Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: reanalysis of Viking Mission data consistent with aromatic organic compounds on Mars

Motivated by the detection of chlorobenzene by the Sample Analysis at Mars instrument suite on the Curiosity rover, and the identification of its carbon source as indigenous to the martian sample, a reexamination was conducted of the original, microfilm preserved, Viking GC-MS data sets. There is evidence for the presence of chlorobenzene in Viking Lander 2 (VL-2) data at levels corresponding to 0.08-1.0 ppb (relative to sample mass), in runs when the sample was heated to 350°C and 500°C. Additionally, there is a correlation between the temperature dependence of the chlorobenzene signal and the dichloromethane signal originally identified by the Viking GC-MS team. Possible sources of carbon that may have produced the chlorobenzene signal were considered, by reaction with perchlorate during pyrolysis, including organic carbon indigenous to the martian parent sample and instrument contamination. The chlorobenzene signal measured by VL-2 likely originated from martian chlorine sources. The carbon source could originate from the martian parent sample, though a carbon source contributed from instrument background cannot yet be ruled out.

II.

Preface

This thesis includes studies based on published articles (Chapter II, Chapter III) and manuscripts in preparation (Chapter IV). The thesis also contains an introduction (Chapter I) and a perspectives chapter (Chapter V), the latter of which presents (i) a review of demonstrated detections of amino acids utilizing MTBSTFA derivatization and their applicability to space experimentation and (ii) the implications of preliminary testing of thermodesorption and derivatization testing of natural samples on laboratory setups for future optimization studies in the context of space experiments. A conclusions chapter completes the thesis by summarizing the main results, conclusions, and recommendations of this thesis as well as future work that can be done as a continuation to the work presented here.

The following published articles are a part of this thesis. [START_REF] Guzman | Identification of Chlorobenzene in the Viking Gas Chromatograph-Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars[END_REF]. Identification of chlorobenzene in the Viking gas chromatograph-mass spectrometer data sets: Reanalysis of Viking mission data consistent with aromatic organic compounds on Mars. Journal of Geophysical Research: Planets, 123. https://doi.org/10.1029/ 2018JE005544 Guzman, M., [START_REF] Guzman | Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars[END_REF]. Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars. Planetary and Space Science, 186. https://doi.org/10.1016/j.pss.2020.104903

Abstract

The question of whether or not terrestrial life is alone in the universe is a philosophical and scientific question that has captivated humanity since ancient times. This thesis approaches its science and technical questions from the foundational scientific idea that life is composed of, and generates, organic matter. Additionally, organic matter of biological origin may be differentiated from abiotic matter as life can preferentially select and use specific organic molecules. The search for life, and the environmental ingredients necessary to sustain life, on Mars have revealed that the martian environment has had the prerequisite environmental ingredients and preservation potential, alongside destructive forces for organic matter, for the development of life in its past or even in its present in the subsurface. This thesis focuses on the search for organic matter using the Viking Lander Gas Chromatograph-Mass Spectrometer (GC-MS) and the future ExoMars Mars Organic Molecule Analyser (MOMA) GC-MS experiments, with applications also to the Sample Analysis at Mars (SAM) experiment onboard the Mars Science Laboratory (MSL).

In Chapter II, the original, microfilm preserved, Viking gas chromatograph-mass spectrometer data sets are reexamined, motivated by the detection of chlorobenzene by the SAM instrument suite on the Curiosity rover, and the identification of its carbon source as indigenous to martian samples. There is evidence for the presence of chlorobenzene in Viking Lander 2 (VL-2) data at levels corresponding to 0.08-1.0 ppb (relative to sample mass), in runs when the sample was heated to 350°C and 500°C. Additionally, there is a correlation between the temperature dependence of the chlorobenzene signal and the dichloromethane signal originally identified by the Viking GC-MS team. Possible sources of carbon that may have produced the chlorobenzene signal are considered, by reaction with perchlorate during pyrolysis, including organic carbon indigenous to the martian parent sample and instrument contamination. It is concluded that the chlorobenzene signal measured by VL-2 originated from martian chlorine sources. The carbon source could originate from the martian parent sample, though a carbon source contributed from instrument background cannot yet be ruled out.

MOMA could be called the child of Viking, in that it will conduct an inventory of the organic molecular composition at the martian surface, but as a function of depth below the martian surface. MOMA is an instrument onboard the Rosalind Franklin rover that is scheduled to be launched to Mars in the summer of 2022 as part of the ExoMars mission. This experiment includes a GC-MS instrument dedicated to the in situ analysis of organic molecules, and their enantiomers, present in martian samples collected by the rover at the surface down to 2 m depth. In order to evaluate the performance of the integrated chromatographic system which was selected for the flight model, experiments were carried out with a laboratory setup that reproduced the flight configuration and mimicked the in situ operating conditions (Chapter III). Chapter III shows that the column instrument package can separate and detect a wide range of organic and inorganic volatile compounds, from noble gases to hydrocarbon chains with up to 29 carbon atoms (C29). A laboratory study of the enantiomeric resolution of selected chiral chemical standards is compared to: i. tests performed with the same instrumental setup but using a natural sample spiked with amino acids in order to evaluate the influence of a mineral phase on the analysis, and ii. tests run on a MOMA engineering test unit (ETU) which is representative of the flight model. Tests on the more complex sample and the more flight-like instrument allows a comparison with laboratory results, in order to confirm that laboratory data are reliable for supporting peak identification within flight data. The obtained results demonstrate the ability of the gas chromatographic subsystem to identify a wide range of organic and inorganic volatile compounds, including biomolecular signatures, within the constrained space operating conditions of MOMA. The results form a retention time and mass spectral database for MOMA which will be critical for analysis of the eventual flight data.

Continuing the study of the capabilities of the MOMA GC-MS experiment, GC-MS analyses were conducted on samples containing four potential representative organic compounds, adenosine 5'monophosphate (AMP), L-glutamic acid (Glu), L-phenylalanine (Phe), and phthalic acid (PhA), which have been adsorbed on to a mineral, montmorillonite (Mont), at three concentrations (5, 1, 0.1 wt. %) and with or without the addition of magnesium perchlorate. These samples were tested using MOMA-like pyrolysis and wet chemistry (derivatization, thermochemolysis) protocol coupled to GC-MS analysis. Many studies have explored the capabilities of the GC-MS analytical and wet chemistry protocols using chemical standards, but it is yet to be fully explored how the solid mineral matrix of samples may impact the analysis. The presence of salts and a mineral matrix have been shown to deactivate or reduce the derivatization reaction efficiency. It is also known that the presence of perchlorate in martian samples can cause potential problems for detection of organics by GC-MS. This study demonstrates that (i) the derivatization reaction is preserved in the presence of salts and in the presence of montmorillonite clay, (ii) the presence of the mineral matrix likely does influence the number and types of organic products based on catalytic or preservative effects and based on the specific adsorption efficiency and location of organics to the mineral, (iii) chlorinated hydrocarbons are produced during the higher temperature analyses (pyrolysis and thermochemolysis), but detection of target organics are not hindered at the tested concentrations, and (iv) the MOMA GC-MS package enables detection of each target organic molecule or its products in the presence of a clay mineral across the multiple GC-MS submodes, while certain sub-modes have limitations for the detection of certain compounds in this sample set. These results will be important analog GC-MS runs during MOMA operations on Mars in order to predict and identify compounds of interest, including degradation and reaction products, in flight chromatograms.

The initial experimental chapters of this thesis (Chapters III-IV) explore the laboratory analysis of relatively straight-forward samples (chemical standards, mineral samples with a single spiked organic compound) using commercial off-the-shelf (COTS) laboratory GC-MS setups. However, there are specific complexities to natural samples (e.g., suites of species, trace organics) and to space experimentation (e.g., complex gas processing systems, adsorption/desorption trapping) that may present unique challenges for strict detection of target compounds such as amino acids. A perspectives chapter (Chapter V) explores the demonstrated detections of amino acids using Nmethyl-N-tert-butyl-dimethylsilyltrifluoroacetamide (MTBSTFA) derivatization through a review from the literature of demonstrated detections of amino acids using MTBSTFA derivatization, with focused attention on the complexity of the sample under testing and to the fidelity of the experimental setup to space-like experimentation on SAM and MOMA. Laboratory experimental setups for derivatization testing of natural samples are explored, with examples from preliminary results and a discussion of the pros and cons of each setup for its applicability and usefulness to the implementation of the space experiment. Perspectives for future laboratory testing of flightlike derivatization and thermodesorption testing of natural samples are also presented.

In summary, the results presented in this thesis reevaluate the interpretation of past Mars GC-MS mission data (Viking, Chapter II) and will collectively aid in the implementation of Mars operations and the valid and accurate interpretation of potential data obtained by the MOMA instrument during the ESA/Roscosmos ExoMars 2022 rover mission (Chapter III-V). The studies show the capabilities and limitations of the planned GC-MS analysis. In addition, this thesis offers results and commentary that can be applied to the interpretation of the SAM GC-MS analysis currently operating on Mars.

Résumé

La question de savoir si la vie terrestre est seule dans l'univers est une question philosophique et scientifique qui a captivé l'humanité depuis l'Antiquité. Cette thèse aborde ses questions scientifiques et techniques à partir de l'idée que la vie est composée et génère de la matière organique. Elle se concentre sur la recherche de matière organique à la surface de Mars par chromatographie en phase gazeuse-spectrométrie de masse (GC-MS) à bord de l'atterrisseur Viking, de la future mission ExoMars Mars Organic Molecule Analyzer (MOMA), et avec quelques applications à l'analyse d'échantillons at Mars (SAM) à bord du Mars Science Laboratory (MSL). Dans le cadre de cette thèse, les ensembles de données Viking GC-MS ont été réexaminés et des preuves ont été découvertes soutenant la présence de chlorobenzène, un produit de réaction potentiel du carbone martien et du chlore martien pendant la pyrolyse. Le MOMA pourrait être appelé « l'enfant de Viking », dans la mesure où il effectuera un inventaire de la composition moléculaire organique à la surface martienne, mais en fonction de la profondeur sous la surface martienne. MOMA est un instrument embarqué à bord du rover Rosalind Franklin qui devrait être lancé entre Mars et l'été 2022 dans le cadre de la mission ExoMars. Cette expérience comprend un instrument GC-MS dédié à l'analyse in situ de molécules organiques, et de leurs énantiomères, présentes dans des échantillons martiens collectés par le rover en surface jusqu'à 2 m de profondeur. Afin d'évaluer les performances du système chromatographique intégré qui a été sélectionné pour le modèle de vol, des expériences ont été réalisées avec une configuration de laboratoire reproduisant la configuration de vol et imitant les conditions de fonctionnement in situ (chapitre III). Le chapitre III montre que l'ensemble d'instruments à colonne peut séparer et détecter une large gamme de composés volatils organiques et inorganiques, des gaz rares aux chaînes d'hydrocarbures contenant jusqu'à 29 atomes de carbone (C29). Une étude en laboratoire de la résolution énantiomérique d'étalons chimiques chiraux sélectionnés est comparée à : i. des tests réalisés avec le même montage instrumental mais en utilisant un échantillon naturel dopé en acides aminés afin d'évaluer l'influence d'une phase minérale sur l'analyse, et ii. tests réalisés sur une unité d'essais d'ingénierie (ETU).

MOMA est représentative du modèle de vol. Les tests sur l'échantillon le plus complexe et l'instrument le plus proche du vol permettent une comparaison avec les résultats de laboratoire, afin de confirmer que les données de laboratoire sont fiables pour soutenir l'identification des pics dans les données de vol. Les résultats obtenus démontrent la capacité du sous-système de chromatographie en phase gazeuse à identifier une large gamme de composés volatils organiques et inorganiques, y compris les signatures biomoléculaires, dans les conditions d'exploitation spatiales restreintes de MOMA. Les résultats forment une base de données de temps de rétention et de spectre de masse pour MOMA qui sera critique pour l'analyse des données de vol éventuelles. Ensuite, le protocole de pyrolyse et de chimie humide MOMA GC-MS est exploré avec un ensemble plus complexe d'échantillons dans lesquels les composés organiques sont absorbés sur une matrice minérale de montmorillonite en fonction des concentrations et avec ou sans addition de perchlorate de magnésium. Cette étude montre que le package MOMA GC-MS permet la détection de chaque molécule organique cible ou de ses produits en présence du minéral argileux. Enfin, la thèse présente des perspectives sur les complexités spécifiques aux échantillons naturels plus complexes (par exemple, suites d'espèces, traces de matières organiques) et à l'expérimentation spatiale (par exemple, systèmes complexes de traitement de gaz, piégeage par adsorption / désorption) qui peuvent présenter des défis uniques pour les expériences de surface de Mars dans l'identification stricte des composés cibles tels que les acides aminés. Les résultats présentés dans cette thèse réévaluent l'interprétation des données de la mission précédente Mars GC-MS et aideront collectivement à la mise en oeuvre des opérations de surface de Mars et à l'interprétation des données potentielles obtenues par l'expérience MOMA d'ExoMars. De plus, cette thèse propose des résultats et des discussions qui peuvent être appliqués à l'interprétation de l'analyse SAM GC-MS actuellement en cours sur Mars. The question of whether or not terrestrial life is alone in the universe is a philosophical and scientific question that has captivated humanity since ancient times. Astrobiology explores such questions using a multidisciplinary and multipronged approach by combining measurements collected from the remote sensing of other planetary bodies, the in situ analysis of planetary surfaces and atmospheres, and the analog simulation of planetary environments and space experiments in the laboratory. The search for life, and the environmental ingredients necessary to sustain life, are contextualized by the formation of life on our own planet, Earth, and its environmental and physiochemical processes between 3.5 and 2.8 billion years ago [START_REF] Schopf | Cradle of Life: The Discovery of Earth's Earliest Fossils[END_REF]. This section explores the conditions and the ingredients necessary for the emergence of life on Earth which provide context in exploring other planetary environments and their ability to sustain life. This section also discusses what astrobiologists define as signatures and indications of life (bioindicators and biosignatures are discussed in Section I.1.2) which then set the foundations for quantitative measurement.

Acronyms

I.1.1. Conditions necessary for the emergence of life

Life on Earth reveals fundamental biochemical and genetic principles which underlie all life. The main polymers of biology (nucleic acids, proteins, and polysaccharides) are built from the same building blocks of 20 amino acids, 5 nucleotide bases and sugars. [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF] describes these components, along with lipids and fatty acids, as the hardware of life, with DNA and RNA forming a common software [START_REF] Lehninger | Biochemistry[END_REF][START_REF] Woese | Bacterial evolution[END_REF]. However, no single definition of life is agreed upon among scientists and philosophers alike. [START_REF] Koshland | The Seven Pillars of Life[END_REF] lists seven features of life, including programming (DNA), improvisation (response to environment), compartmentalization, energy, regeneration, adaptability, and seclusion (chemical control and selectivity). A simpler definition is that life is a material system that undergoes reproduction, mutation, and natural selection [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF]. [START_REF] Cleland | Defining 'Life'. Origins of life and evolution of the biosphere[END_REF] suggests that life might be like water, hard to define phenomenologically, but easy to define at the fundamental level, while [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF] suggests life is more alike to fire, a process, not a pure substance. Practical approaches to the search for life on other worlds have mainly targeted habitability by determining what life needs and to search for that. Other frameworks and related measurement techniques have been geared toward life detection from the perspective of searching for evidence of life (Section I. 1.2) based on what is known about terrestrial life. There are also initiatives to form frameworks for the measurement of agnostic biosignatures which consider signs of life on other worlds as independently from terrestrial biology as possible [START_REF] Johnson | Fingerprinting Non-Terran Biosignatures[END_REF].

The simplest list of what life needs, and therefore the list of what to search for on other worlds, includes energy, organic molecules, and liquid water [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF][START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF], although it is important to note that the conditions required for the emergence of life may be more stringent than for the sustainability of life. Metals and minerals such as calcium are also required in terrestrial life as construction materials in living organisms or to catalyze reactions. Life requires energy to maintain itself against entropy, as does any self-organizing open system. The presence of an energy source is essential for the activation of chemical reactions leading to the complexification of organic molecules into macromolecules. On Earth, the vast majority of lifeforms ultimately derive their energy from sunlight. The only other known source of primary productivity is chemical energy, and there are only two known ecosystems, both methanogen-based [START_REF] Chapelle | A hydrogen-based subsurface microbial community dominated by methanogens[END_REF][START_REF] Stevens | Lithoautotrophic Microbia, Ecosystems in Deep Basalt Aquifers[END_REF], that rely exclusively on chemical energy [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF]. Photosynthetic organisms can use sunlight at levels below the level of sunlight at the orbit of Pluto [START_REF] Raven | Put out the light, and then put out the light[END_REF]; therefore, energy is not the limitation for the existence of life [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF]. Some frameworks suggest that the biological demand for energy should be fundamental for determining habitability and the potential for the development of life on other worlds, as illustrated in Figure 1 [START_REF] Hoehler | An energy balance concept for habitability[END_REF]. Energy contributions necessary for biological activities within living organics (e.g., replication of DNA) may have been found on primitive Earth in different forms, including internal heat sources such as geothermal energy resulting from the disintegration of radioactive elements contained in the Earth's mantle, also at the origin of volcanism [START_REF] Martin | Hydrothermal vents and the origin of life[END_REF] or external heat sources such as electric discharges within the atmosphere [START_REF] Miller | A Production of Amino Acids Under Possible Primitive Earth Conditions[END_REF]. Sources of radiation, generally UV radiation coming from a planetary system's star [START_REF] Chyba | Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life[END_REF] or a contribution of energetic particles, are components of environments with energy gradients favorable to redox reactions occurring in serpentinization regions [START_REF] Mccollom | Serpentinites, Hydrogen, and Life[END_REF][START_REF] Russell | Serpentinization as a source of energy at the origin of life[END_REF] or in rocks where the natural catalytic and reactive qualities of transition metal sulfides [START_REF] Cody | TRANSITION METAL SULFIDES AND THE ORIGINS OF METABOLISM[END_REF][START_REF] Huber | Peptides by activation of amino acids with CO on (Ni,Fe)S surfaces: implications for the origin of life[END_REF] have been conducive to the development of life on primitive Earth.

Life uses organic molecules as its basic building blocks. These building blocks consist of at least a carbon skeleton associated with one or more hydrogen atoms. The set of atoms used by living organisms are carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur, commonly known as CHNOPS. These atoms come together to reach the level of complexity characterizing living systems [START_REF] Henning | Carbon in the Universe[END_REF]. However, it is also now known that the universe is full of the atoms that make up the building blocks of life and they are continually combining to form organic molecules through abiotic processes [START_REF] Kwok | Complex organics in space from Solar System to distant galaxies[END_REF]. Once organic molecules are formed in the universe, they can be accreted, either directly during the formation of planets and objects in the solar system, or brought to planetary surfaces by these same planetary bodies and objects after their formation. Indeed, the Sun and the outer Solar System have more than 10,000 times the carbon content of the bulk of Earth [START_REF] Mckay | Urey prize lecture: Planetary evolution and the origin of life[END_REF]. This is the reason why organic molecules have been identified in each of these planetary bodies [START_REF] Botta | Extraterrestrial Organic Compounds in Meteorites[END_REF][START_REF] Goesmann | Organic compounds on comet 67P/Churyumov-Gerasimenko revealed by COSAC mass spectrometry[END_REF][START_REF] Pizzarello | The Nature and Distribution of the Organic Material in Carbonaceous Chondrites and Interplanetary Dust Particles[END_REF]) and were probably already present during formation. Additionally, these compounds can be delivered to planetary surfaces via exogenous sources of organic matter or can be synthesized within primitive atmospheres, favored by a predominantly reducing environment, activated by energy sources (UV radiation and/or electric discharges) [START_REF] Bernstein | Prebiotic materials from on and off the early Earth[END_REF]), but also on the surface, when liquid water interacts with minerals [START_REF] Hazen | Mineral surfaces, geochemical complexities, and the origins of life[END_REF]James Cleaves Ii et al. 2012) or from chemical reactions in hydrothermal vents [START_REF] Konn | The production of methane, hydrogen, and organic compounds in ultramafic-hosted hydrothermal vents of the Mid-Atlantic Ridge[END_REF][START_REF] Mccollom | Abiotic Synthesis of Organic Compounds in Deep-Sea Hydrothermal Environments[END_REF], 2013;[START_REF] Mccollom | Investigation of extractable organic compounds in deep-sea hydrothermal vent fluids along the Mid-Atlantic Ridge[END_REF]. The endogenous and exogenous sources of organic matter with an application to Mars will be discussed in Section I.2.3.1. The effects of sources of radiation and oxidation are also discussed in the context of preservation of organics in Section I.2.3.2.

and preservation of organic matter on a planetary surface. The focus will also be on the presence of organic matter in surface materials rather than atmospheric, again recognizing that the processes are linked and discussing these links when applicable. In the next section, types of complex organic molecules are discussed as well as their characteristics which can arise in the essential conditions discussed in this section and which form the basis for designing experiments and making measurements which can indicate the presence of extinct or extant life on other worlds.

I.1.2. Biomarkers and bioindicators

While it is possible that extraterrestrial organisms exist based on a different type of chemistry than the terrestrial carbon-hydrogen-nitrogen-oxygen chemistry, the astrobiology community seeks in priority a life resembling that which is known on Earth. The search for extraterrestrial life is based on a search for phenomena that could only have been produced by extinct or extant life. A biosignature is defined by the most recent NASA Astrobiology Strategy as an object, substance, and/or pattern whose origin specifically requires a biological agent (NASA 2015). A biomarker or biosignature is a phenomenon that can be interpreted without ambiguity as having been produced by life. A bioindicator is a phenomenon that could have been produced by life, but also has a possible abiotic origin. Different groupings and types of categorical work for biomarkers and bioindicators exist in the community to distinguish between types of measurements such as chemical (e.g., elementary composition, isotopic ratios, chirality), morphological (macroscopic and microscopic inspection of the surface of samples), or a global signature (e.g., the infrared signature of atmospheric carbon dioxide can indicate a telluric exoplanet, the presence of water, a detection of O3). Biosignatures have been categorized and discussed at length in the community and are sometimes an open topic of debate. There are some debates about the probability or robustness of a detection of life using the detection of only one biosignature. Confidence frameworks for the biology-related science objectives of life detection and habitability missions are discussed in Section I. 1.3 and shown for the ExoMars 2022 mission in Figure 7.

Morphological signatures such as the presence of fossils of multicellular organisms in an extraterrestrial environment would be irrevocable proof of the presence of extant or extinct life, though it can be difficult to deconvolute the biotic or abiotic origin of certain structures [START_REF] Mckay | Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001[END_REF][START_REF] Mittlefehldt | ALH84001, a cumulate orthopyroxenite member of the martian meteorite clan[END_REF]. To be recognized as biomarkers, microbial fossils should therefore have physicochemical attributes clearly indicating the biotic origin of these structures. Sedimentary structures of microbial origin such as benthic microbial communities on Earth are likely to influence the microstructure of deposits that accumulate in their presence, e.g., stromatolites [START_REF] Schopf | Evidence of Archean life: Stromatolites and microfossils[END_REF]). Microbial films and mats are other sedimentary structures of microbial origin that can leave bioindicators. Mineral signatures, or inorganic solids produced by living organisms, can serve as markers or indicators of life (biomineralization), such as silicates formed by algae and diatoms, carbonates by invertebrates, and calcium phosphates and carbonates by vertebrates [START_REF] Westall | Biosignatures on Mars: What, Where, and How? Implications for the Search for Martian Life[END_REF]. Isotopic signatures such as isotopic carbon ratios ( 13 C/ 12 C or δ 13 C) are biomarkers and have been used to search for traces of life on Earth [START_REF] Mojzsis | Evidence for life on Earth before 3,800 million years ago[END_REF][START_REF] Van Zuilen | Reassessing the evidence for the earliest traces of life[END_REF], as well as to determine the origin of extraterrestrial organic molecules found in meteorites [START_REF] Botta | Extraterrestrial Organic Compounds in Meteorites[END_REF] since in general, the 13 C/ 12 C ratio is lower in living things than in the inorganic world. Other isotopic ratios can be used as bioindicators due to fractionation during bacterial metabolism such as deuterium-to-hydrogen (D/H) ratios [START_REF] Brack | An integrated exobiology package for the search for life on Mars[END_REF] or isotopic analysis of other elements (e.g., O, N and S).

Metabolic signatures from both catabolism (processes of breakdown of complex molecules into simpler molecules) and anabolism (processes of the synthesis of complex molecules from simple molecules, such as the synthesis of proteins from amino acids) can serve as biomarkers and bioindicators. Molecules such as adenosine triphosphate (ATP), a universal molecule of energy coupling which has been retained during evolution and used in metabolic processes, could be a strong indication in favor of a past or present life, although the molecule is fragile and may degrade quickly on planetary geological time scales [START_REF] Schuerger | Slow degradation of ATP in simulated martian environments suggests long residence times for the biosignature molecule on spacecraft surfaces on Mars[END_REF]). However, certain metabolic products or intermediates may be targeted, including biogenic gases such as dioxygen (O2), which is produced during photosynthesis by photoautotrophic organisms, as well as ozone, (O3), nitrous oxide (N2O), and methane (CH4), which are produced by photolysis. N2O is produced during denitrification (microbial conversion of nitrates into nitrites and then into gaseous nitrogen compounds) while CH4 can be produced by microorganisms during methanogenesis. Other compounds are produced by certain metabolisms, such as dimethyl sulfide (DMS), which is produced by phytoplankton on Earth. These sorts of indicators require deconvolution from potential abiotic sources; for example, detection of CH4 could indicate a biotic source, but can also be explained by an abiotic process [START_REF] Des Marais | Remote sensing of planetary properties and biosignatures on extrasolar terrestrial planets[END_REF].

The usefulness of a biosignature is determined not only by the probability of life creating it, but also by the improbability of non-biological processes producing the signature, which could result in a false positive. Thus, investigations into biosignatures must also consider how such signatures could be generated, preserved, and/or detected within the context of other environments (NASA 2015). The NASA Astrobiology Strategy report groups biosignatures and habitable environment signatures into ten broad categories, including stable isotope patterns, chemical features that require biological activity, organic matter, minerals, microscopic structures and textures, macroscopic physical structures and textures, temporal variability, surface reflectance features, atmospheric gases, and technosignatures (NASA 2015). A Science Definition Team for the Mars 2020 rover identified six types of potential biosignatures as illustrated in Figure 2. The work of this thesis is related to the investigation of organic matter and of chemical features of this matter that require biological activity. This thesis will focus primarily on the detection of biopolymers, their monomers, and other organic molecules which are of interest as biomarkers and bioindicators (Section I.1.2.1 and Section I.1.2.2).

I.1.2.1. Organic matter as the building blocks of life

This thesis operates based on the idea that life is composed of, and generates, carbon-based (organic) compounds. Terrestrial life is based on the basic unit of the cell. The cell is made up of molecules such as nucleic acids, proteins, polysaccharides, and lipids, which are all considered to be biomarkers since they require synthesis by organisms. However, these macromolecules can be easily degraded by several natural processes such as the presence of powerful oxidants as well as exposure to ionizing radiation that could destroy or alter such molecules (Section I.2.3.2). For example, while DNA is able to withstand certain conditions for thousands of years, RNA degrades much faster [START_REF] Pääbo | Genetic analyses from ancient DNA[END_REF]). Upon the death of living organisms, their organic matter can also be transformed by microorganisms (e.g., the formation of kerogens by biochemical diagenesis). The degradation of these biomarkers leads to their monomers, including nitrogenous bases, amino and polysaccharides (formed from 10 to several thousand ose, also called polysaccharides).

Heterosides and polysaccharides have important functions in living things. There are homogeneous polysaccharides and heterogeneous polysaccharides. Homogeneous polysaccharides are formed by the repetitive condensation of an ose by a sugar link and have two types of functions, including as biological energy reserves, and to provide structure, e.g., polysaccharides that form the frameworks of the exoskeletons of algae, plants (cellulose) and animals (chitin shell of arthropods). Heterogeneous polysaccharides are different chains of oses (or derivatives), most of the time limited to two types: gums (hydrophilic part of the secretions of certain plants) and agar (red algae extract used in microbiology for cell culture). Heterosides are molecules resulting from the covalent association of carbohydrates with other types of molecules, for example glycolipids (lipids from membranes carrying oligo or polysaccharide chains) or glycoproteins (proteins on which short carbohydrate chains are grafted).

I. 1.2.1.4. Lipids Lipids are hydrophobic or amphiphilic molecules of various structures, having numerous and varied biological functions, such as energy storage and production (triglycerides), the structure of cell membranes (the amphiphilic property of phospholipids allowing them to form a double membrane), and the transmission of hormonal messages. They are also synthesized via complex metabolic processes. Fatty acids, in particular, have various roles within the cell, such as energy storage (as triglycerides stored in adipose tissue), structure (they participate in the synthesis of phospholipids, constituents of cell membranes), and hormonal messaging (precursors of several hormones). They are synthesized by living organisms during lipogenesis. During their degradation, fatty acids can be transformed into carboxylic acids, which are much more resistant to degradation. Additional properties of lipids which can be biomarkers are discussed in Section I.1.2.2.

I. 1.2.1.5. Carboxylic acids [START_REF] Benner | The missing organic molecules on Mars[END_REF] considered the hypothesis that a powerful oxidant present in the martian regolith would convert all organic molecules into CO2, and concluded that carboxylic acids, specifically non-volatile salts of benzenecarboxylic acids, and possibly oxalic acid and acetic acid, should be present in the martian regolith as metastable intermediates in the oxidation of meteorite organic compounds under martian conditions (Figure 5). Formic acid, the simplest of the carboxylic acids, has been detected in the most arid zone of the Atacama Desert (an analogue of martian soil), an environment hostile to life [START_REF] Navarro-González | Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life[END_REF]. The destruction of organic matter on Mars by oxidation is further discussed in Section I.2.3.2.

I. 1.2.1.6. Complex organic matter Kerogens, insoluble organic solids of a mixed aromatic and aliphatic nature, can be formed on Earth in part by the sedimentation and degradation of organic matter left behind by dead organisms. An open area of research exists on the presence of polycyclic aromatic hydrocarbons (PAHs), apolar organic molecules that contain at least two benzene rings and can be arranged in different configurations, in the interstellar medium and their potential origin and evolution if present [START_REF] Gudipati | In-situ probing of radiation-induced processing of organics in astrophysical ice analogs-novel laser desorption laser ionization time-of-flight mass spectroscopic studies[END_REF][START_REF] Kwok | Mixed aromatic-aliphatic organic nanoparticles as carriers of unidentified infrared emission features[END_REF][START_REF] Öberg | The Spitzer ice legacy: ice evolution from cores to protostars[END_REF]. [START_REF] Kwok | Mixed aromatic-aliphatic organic nanoparticles as carriers of unidentified infrared emission features[END_REF] suggest that potential signatures of PAHs in the interstellar medium is more likely to be complex organic Low molecular weight amino acids such as glycine (Gly) and alanine (Ala) dominate in abiotic systems, where the relative abundance of amino acids is set by thermodynamic equilibrium conditions that favor the synthesis of smaller molecules with the lowest free energy of formation [START_REF] Higgs | A Thermodynamic Basis for Prebiotic Amino Acid Synthesis and the Nature of the First Genetic Code[END_REF]. On the other hand, higher molecular weight amino acids tend to predominate in systems with biological activity, in which environmental adaptations have been optimized for polymer function and stability. Therefore, the distribution between low molecular weight (e.g., Gly, Ala) and higher molecular weight amino acids (e.g., Ser, Val, Leu), in the case that suites of amino acids are detected in a sample, could serve to differentiate between a biotic and abiotic origin for these compounds [START_REF] Davila | Chance and necessity in biochemistry: implications for the search for extraterrestrial biomarkers in Earth-like environments[END_REF][START_REF] Higgs | A Thermodynamic Basis for Prebiotic Amino Acid Synthesis and the Nature of the First Genetic Code[END_REF].

I.1.2.2.2. Chain-length distributions and carbon-number patterns in lipids

On Earth, patterns in carbon number are uniquely produced by the presence of past or present life. For example, terrestrial life uses C2-acetate and C5-isoprene subunits in the biosynthesis of phospholipid fatty acids and isoprenoid lipids, respectively [START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF][START_REF] Georgiou | Lipids as Universal Biomarkers of Extraterrestrial Life[END_REF][START_REF] Summons | Molecular Biosignatures[END_REF]). The addition of C2 subunits results in an even-over-odd predominance in carboxylic acid chain lengths or odd-over-even predominance in derivative species such as alkanes. A repeated C5 predominance in isoprenoids is also maintained in derivatives species. On the other hand, abiotic synthesis is random and leads to non-patterning [START_REF] Dorn | Monomer Abundance Distribution Patterns as a Universal Biosignature: Examples from Terrestrial and Digital Life[END_REF][START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF][START_REF] Summons | Molecular Biosignatures[END_REF]. Chain-length distributions as a function of carbon number in lipids are also considered as a biosignature for terrestrial life. C12 to C30 lipid hydrocarbons are typical of terrestrial cellular membranes [START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF]. On the other hand, the abiotic synthesis of hydrocarbon chains is indicated by short chain lengths (<C8) with an exponential decay in molecular abundance as a function of carbon number. Longer chain lengths (>C12) are rarely produced by abiotic processes [START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF][START_REF] Georgiou | Lipids as Universal Biomarkers of Extraterrestrial Life[END_REF][START_REF] Summons | Molecular Biosignatures[END_REF], except in the case of water-rock reactions such as the Fischer-Tropsch process [START_REF] Mccollom | Methanogenesis as a potential source of chemical energy for primary biomass production by autotrophic organisms in hydrothermal systems on Europa[END_REF][START_REF] Mccollom | The influence of carbon source on abiotic organic synthesis and carbon isotope fractionation under hydrothermal conditions[END_REF][START_REF] Mccollom | Abiotic Synthesis of Organic Compounds in Deep-Sea Hydrothermal Environments[END_REF]. In addition to an affinity for >C12 chain-length, biological samples also have modal or clustered distributions at higher chain length. For example, a predominance of C16-C20 chains is commonly observed in terrestrial organisms [START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF][START_REF] Summons | Molecular Biosignatures[END_REF]. Distillation processes can modify the chainlength distributions at low or high ends of the range, but rarely generate clusters. Detectable targets include straight or branched, saturated or unsaturated carboxylic acids and fatty acids, alcohols, alkenones or amines, bound lipids, such as phospholipids, or geological derivatives, such as alkanes and alkenes. Some of these molecules are targeted in the studies described in Chapter III and IV of this thesis.

I.1.3. Confidence frameworks for biology-related science objectives

The principle ingredients for life on a planetary body include liquid water, suitable energy source(s), and the presence of essential elements for biology, including organic matter. Organic matter is a prerequisite ingredient for the formation of life as well as can be produced by life and therefore leave behind indications or evidence of past or present life on another planet. The search for traces of past or present life in extraterrestrial environments allows us to obtain evidence on the possibility of life elsewhere beyond the Earth, in the form of evidence (biomarkers), such as fossils, sedimentary structures of mineral origin, isotopic or metabolic signatures, and biopolymers such as DNA, proteins, and polysaccharides. Investigations can also target clues (bioindicators),

that geologic history on the potential for traces of life on Mars today as well as potential sources of organic molecules at the surface of Mars.

I.2.1. Geologic periods in Mars history

Based on the density of meteorite impact craters in a region, the relative stratigraphy method allows dating of martian terrains (Hartmann & Neukum 2001). A theoretical model of the number of craters and the type of impact as a function of time was established using data of lunar craters following the return of samples from the Apollo missions which allows absolute dating of land [START_REF] Neukum | Cratering Records in the Inner Solar System in Relation to the Lunar Reference System[END_REF][START_REF] Stöffler | Stratigraphy and Isotope Ages of Lunar Geologic Units: Chronological Standard for the Inner Solar System[END_REF]. The history of Mars has been divided into three major geological periods:

(1) the Noachian, from -4.1 to 3.7 billion years ago;

(2) the Hesperian, from -3.7 to 3.0 billion years ago;

(3) the Amazon from -3.0 billion years ago to today.

The period from the formation of Mars (-4.56 Ga) to -4.1 billion years, of which there would be almost no trace remaining, is called the pre-Noachian. This period began with the accretion of the planetesimals that formed Mars, the differentiation of Mars, and the formation of the martian crust [START_REF] Brasser | Oort cloud and Scattered Disc formation during a late dynamical instability in the Solar System[END_REF][START_REF] Dauphas | Hf-W-Th evidence for rapid growth of Mars and its status as a planetary embryo[END_REF][START_REF] Mezger | Core Formation and Mantle Differentiation on Mars[END_REF]. Mars then experienced a period of intense bombardment, marked by intense geophysical activity such as volcanism [START_REF] Werner | Theoretical analysis of secondary cratering on Mars and an image-based study on the Cerberus Plains[END_REF]) and potential plate tectonics [START_REF] Breuer | Early plate tectonics versus single-plate tectonics on Mars: Evidence from magnetic field history and crust evolution[END_REF]. A magnetic field likely protected the martian surface from energetic radiation.

The Noachian period is characterized by either perennial precipitation on a global scale or episodic precipitation, with morphological and mineralogical indicators testifying to the presence of liquid water at the martian surface during this period (Section I.2.2.2). Volcanic activity continued during the Hesperian period [START_REF] Carr | Geologic history of Mars[END_REF], though liquid water flows became rarer and climatic conditions began to change in that the planet became colder with a thinner atmosphere. Finally, activity during the Amazonian period is more limited, including mainly glacial and/or wind hydrological processes as the planet gradually turns into a cryosphere. Amazonian aeolian processes involve the erosion of rocks at the martian surface, in which the most friable rocks fragmented into grains and dust [START_REF] Sullivan | Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site[END_REF] as evidenced by the thick layer of dust present today on the surface and in the martian dune fields.

Figure 8 represents the chronological map of the martian surface, established by dating of geological terrains [START_REF] Bouvier | Martian meteorite chronology and the evolution of the interior of Mars[END_REF][START_REF] Breuer | Early plate tectonics versus single-plate tectonics on Mars: Evidence from magnetic field history and crust evolution[END_REF]. The oldest martian lands that have been preserved are the highly cratered lands of the Southern Hemisphere, dated between -4.1 and -3.7 Ga, during the Noachian period. Since Mars formed 4.56 Ga ago, at the same time as the Earth, it could have preserved traces of similar prebiotic chemistry or early life in its ancient lands and provided information on its past environmental conditions. The following sections explore evidence of the availability of the ingredients for habitability (Section I.1.1) during martian geologic times and the potential for preservation of organic matter at or near the martian surface given climatic conditions and changes over time. [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF] also proposed a chronology of martian geologic times scales based on the main mineralogical regimes of Mars which are related to the conditions present at the surface. This

Mars is known to have experienced intense geophysical activity evidenced by volcanism [START_REF] Werner | Theoretical analysis of secondary cratering on Mars and an image-based study on the Cerberus Plains[END_REF]) and probably associated with plate tectonics [START_REF] Breuer | Early plate tectonics versus single-plate tectonics on Mars: Evidence from magnetic field history and crust evolution[END_REF]. The gradient of the geothermal flow is therefore a possible energy source and would have been available until volcanism stopped during the Amazonian period. Several mineralogical indices (e.g., serpentine, carbonates, phyllosilicates and silica), distributed throughout the planet, also show evidence of localized hydrothermal activity [START_REF] Abramov | Thermal effects of impact bombardments on Noachian Mars[END_REF][START_REF] Bultel | Detection of Carbonates in Martian Weathering Profiles[END_REF][START_REF] Ehlmann | Geologic setting of serpentine deposits on Mars[END_REF][START_REF] Squyres | Detection of Silica-Rich Deposits on Mars[END_REF] which will be further discussed in Section I.2.3. On Earth, in addition to being highly energetic zones, hydrothermal vents are environments conducive to redox reactions, even to the development of extremophiles or organisms capable of surviving in extreme environments not previously expected to be able to sustain life. Energy sources available on primitive Mars could potentially fuel intramolecular reactions or promote metabolic activity. Additionally, the total available energy provided by meteoritic impacts has been estimated by the thermodynamic properties of mineral alteration involved in these impact events [START_REF] Jakosky | The biological potential of Mars, the early Earth, and Europa[END_REF][START_REF] Varnes | Biological Potential of Martian Hydrothermal Systems[END_REF]. A dense atmosphere, formed via planetary degassing of volatile species, would be rich in H2, H2O, CH4, and CO2 and would support the hypothesis of a hot and humid climate favorable to the subsistence of liquid water on the martian surface [START_REF] Wordsworth | The Climate of Early Mars[END_REF]. Massive and repetitive impacts during the first 500 million years would contribute to an ejection of atmospheric molecules and also to the water supply at the surface and subsurface. Bombardment can also create local hydrothermal vents from the increase in temperature at the point of impact (Section I.2. Hynek 2010). During this period, craters could have been vehicles for water storage, forming lacustrine environments regularly fed by episodic fluvial networks [START_REF] Kraal | Martian stepped-delta formation by rapid water release[END_REF] or over several thousand years [START_REF] Barnhart | Long-term precipitation and late-stage valley network formation: Landform simulations of Parana Basin, Mars[END_REF]. The resurgence of groundwater would cause the formation of other lakes due to perennial and/or episodic precipitation. The flows dating from the Noachian period could have been formed via two distinct processes:

I
(1) Perennial precipitation on a global scale, typically during the establishment of a water cycle as is present on Earth. (2) Episodic precipitation caused by evaporation of the water contained in the soil during frequent meteoritic impacts.

Detections of carbonates in the southern hemisphere [START_REF] Niles | Geochemistry of Carbonates on Mars: Implications for Climate History and Nature of Aqueous Environments[END_REF] and recently on a global scale [START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF] support the hypothesis of a hot and humid Mars during this time period and support a sub-surface rich in hydrothermal activities. The hypothesis of a hot and humid climate is also supported by detections of clays rich in Al and Fe/Mg, compatible with alteration sequences of widespread aqueous matter at the martian surface [START_REF] Carter | Widespread surface weathering on early Mars: A case for a warmer and wetter climate[END_REF]. The detection of hydrated minerals on the surface of Mars may also constitute evidence that water was present in the liquid state during the Noachian period (Section I.2.3.2) [START_REF] Poulet | Abundance of minerals in the phyllosilicate-rich units on Mars[END_REF].

I.2.2.2.3. Liquid water during the Hesperian

During the Hesperian period, liquid water flows become rarer due to the escape of atmospheric molecules under the action of the sun, associated with the precipitation of CO2 into carbonates and the trapping of water in the subsurface, by serpentinization, or in the form of water ice [START_REF] Chassefière | The combined effects of escape and magnetic field histories at Mars[END_REF][START_REF] Lammer | Outgassing History and Escape of the Martian Atmosphere and Water Inventory[END_REF]). However, catastrophic flow morphologies from this period are observed in the northern hemisphere and attest to the presence of liquid water during the Hesperian. Branched valleys like those dating from the Noachian are present to a lesser extent in the Hesperian [START_REF] Hynek | Updated global map of Martian valley networks and implications for climate and hydrologic processes[END_REF], including breakup valleys which have been attributed to catastrophic flows. Hypotheses for the formation of these features include a brutal release of a large quantity of underground water present under the permafrost, causing torrents of violent and massive flooding during their ascent to the surface [START_REF] Dohm | Ancient drainage basin of the Tharsis region, Mars: Potential source for outflow channel systems and putative oceans or paleolakes[END_REF][START_REF] Lasue | Quantitative Assessments of the Martian Hydrosphere[END_REF][START_REF] Wilson | Explosive volcanic eruptions on Mars: Tephra and accretionary lapilli formation, dispersal and recognition in the geologic record[END_REF] or that the valleys were formed via very fluid lava flows [START_REF] Hopper | Formation of Hrad Vallis (Mars) by low viscosity lava flows[END_REF]. Like the river networks, most of the breakup valleys open out into the plains of the Northern Hemisphere at lower altitudes, favoring the hypothesis of a global ocean at the end of the Hesperian. This scenario is supported by geomorphological evidence such as the presence of a shore line [START_REF] Perron | Evidence for an ancient martian ocean in the topography of deformed shorelines[END_REF], deltas [START_REF] Di Achille | Ancient ocean on Mars supported by global distribution of deltas and valleys[END_REF][START_REF] Dibiase | Deltaic deposits at Aeolis Dorsa: Sedimentary evidence for a standing body of water on the northern plains of Mars[END_REF] and geophysical indicators such as the presence of sedimentary deposits in the subsurface [START_REF] Mouginot | Dielectric map of the Martian northern hemisphere and the nature of plain filling materials[END_REF]. Liquid water would have become less stable on the surface during the Hesperian period and would have gradually evaporated as evidenced by the presence of evaporate deposits. The global cooling of the planet is evidenced by the observation of glaciers in the tropics, dating from the end of the Hesperian and water ice deposits at the South Pole, covering 2% of the Hesperian surface [START_REF] Head Iii | Extensive Hesperian-aged south polar ice sheet on Mars: Evidence for massive melting and retreat, and lateral flow and ponding of meltwater[END_REF]. If liquid water was still present at the surface during this period of Mars's history, it was only present in the subsurface, except during the violent and episodic releases due to volcanism and impacts.

I.2.2.2.4. Liquid water during the Amazonian

During the past three billion years, Mars has been gradually transforming into a cryosphere via the loss of water by atmospheric exhaust [START_REF] Villanueva | Strong water isotopic anomalies in the martian atmosphere: Probing current and ancient reservoirs[END_REF]. Its hydrological activity is considerably reduced and activity is limited mainly to glacial and/or wind hydrological processes during this period. River networks formed by localized conditions of volcanism remained active until the last 100 to 200 million years [START_REF] Robbins | The volcanic history of Mars: Highresolution crater-based studies of the calderas of 20 volcanoes[END_REF]. From the beginning of the Amazonian period until today, the largest known water reservoirs on Mars are in the form of water ice and are limited to the polar ice caps from high to mid-latitudes at the surface and subsurface [START_REF] Boynton | Distribution of Hydrogen in the Near Surface of Mars: Evidence for Subsurface Ice Deposits[END_REF][START_REF] Feldman | Hydrated states of MgSO4 at equatorial latitudes on Mars[END_REF][START_REF] Milkovich | North polar cap of Mars: Polar layered deposit characterization and identification of a fundamental climate signal[END_REF][START_REF] Orosei | Radar evidence of subglacial liquid water on Mars[END_REF]. The presence of water ice on the flanks of Olympus Mons suggests that glaciers and the still active volcanism may have interacted until late in the Amazonian [START_REF] Milkovich | Debris-covered piedmont glaciers along the northwest flank of the Olympus Mons scarp: Evidence for low-latitude ice accumulation during the Late Amazonian of Mars[END_REF]. Contemporary flow morphologies (a few million years old) called linear gullies or gullies have recently been observed along the slopes of impact craters. Several scenarios have been proposed to explain their formation, including the sublimation of blocks of water ice or CO2, causing their gradual descent along the slopes and stoppage by friction [START_REF] Diniega | A new dry hypothesis for the formation of martian linear gullies[END_REF]) and sporadic flows of brines which would solidify at lower temperatures than the average martian temperature [START_REF] Goldspiel | Groundwater discharge and gully formation on martian slopes[END_REF][START_REF] Martínez | Water and Brines on Mars: Current Evidence and Implications for MSL[END_REF]. Hydrated salts at several ravines (Recurring Slope Lineae or RSL) have been observed, such as magnesium chlorate salts and perchlorate and sodium perchlorate salts [START_REF] Ojha | Spectral evidence for hydrated salts in recurring slope lineae on Mars[END_REF], possibly signifying the contemporary presence of water in the liquid state at the martian surface; however, recent bodies of evidence have suggested that RSLs are more consistent with dry flows [START_REF] Vincendon | Observational evidence for a dry dust-wind origin of Mars seasonal dark flows[END_REF].

Thin films and near surface water on Mars have recently been suggested to show a water activity >0.7, slightly less favorable to the presence of life than previously thought, at least by most terrestrial standards [START_REF] Sizemore | Habitability of High Latitude Martian Ground Ice, Revisited[END_REF].

I.2.3.

Organic molecules at the surface of Mars: origins, processes, evolution

I.2.3.1.

Past and present origins of organic matter on Mars

The contribution of organic molecules during the Amazonian period of Mars's history comes mainly from exogenous sources such as micrometeorites and interplanetary dust particles (IDPs), which were active since pre-Noachian times. Results from the Curiosity rover at Gale crater, including isotope ratios and the peak temperatures of evolved gases, suggest exogenous input from meteorites and interplanetary dust, and possibly in situ formation processes such as abiotic photosynthesis or electrochemical reduction of CO2 [START_REF] Franz | Indigenous and exogenous organics and surface-atmosphere cycling inferred from carbon and oxygen isotopes at Gale crater[END_REF].

I.2.3.1.1. Exogenous sources of organic matter on Mars

During the formation of the solar system, organic matter was associated with the silicate grains of objects in the interplanetary medium [START_REF] Kwok | Complex organics in space from Solar System to distant galaxies[END_REF]. Since the formation of the solar system, the impact of these objects on the surface of telluric planets allows a continuous supply of organic matter to planetary surfaces [START_REF] Flynn | The delivery of organic matter from asteroids and comets to the early surface of Mars[END_REF]. These objects have been classified, according to their size, into four groups (Rubin & Grossman 2010), including IDPs, micrometeorites, meteorites, and comets and asteroids. Elemental analysis, including that of organic carbon, are possible on these objects in the laboratory due to sample return missions and the natural arrival on Earth of meteorites. Compositional data and knowledge of these objects is discussed in the following sections, which forms the basis for our understanding of potential types and sources of organic matter to be delivered on to the surface of planetary bodies such as Mars. This understanding forms an initial assumption on quantitative availability of organic matter at the surface of Mars before the evolution of that organic matter occurs under Mars surface conditions (Section I.2.3).

The flux of exogenous objects on Mars has been estimated by [START_REF] Flynn | The delivery of organic matter from asteroids and comets to the early surface of Mars[END_REF] who started by simulating the flux of the total exogenous organic matter arriving on the Earth's surface, estimating a carbon input between 10 tons for meteorites to 106 tons for IDPs and micrometeorites. These values were then transposed to Mars, considering Mars's more tenuous atmosphere and lower gravity, which facilitates the intact arrival of objects on the surface. According to these estimates, there would be ten times more carbonaceous matter delivered to Mars than to Earth [START_REF] Flynn | The delivery of organic matter from asteroids and comets to the early surface of Mars[END_REF].

Other studies have estimated ~240 tons of carbonaceous matter provided by micrometeorites in one year, i.e., an average global coverage per year of approximately 0.1 nm [START_REF] Steininger | Influence of magnesium perchlorate on the pyrolysis of organic compounds in Mars analogue soils[END_REF], assuming the organic carbon content is 10% by mass. Other modeling has estimated the delivery rate of organic matter to Mars by meteorites to be about 1.61 tons per year [START_REF] Bland | Meteorite Accumulations on Mars[END_REF], correlating to a flux between 640 and 1280 g of organic carbon per year on the surface of Mars, assuming 2% organic content by mass on average at 2 to 4% of the total falls (carbonaceous chondrites) [START_REF] Millan | Etude de la composition de la surface de Mars : recherche de molécules organiques par analyse physico-chimique in situ avec l'instrument SAM de la mission Mars[END_REF]). This quantity is much less than that provided by micrometeorites and IDPs [START_REF] Millan | Etude de la composition de la surface de Mars : recherche de molécules organiques par analyse physico-chimique in situ avec l'instrument SAM de la mission Mars[END_REF]. Estimates of the total accumulated carbonaceous matter on the surface of Mars assume a constant flux over time, which is likely not the case, with more intense flows during early periods in Mars's past [START_REF] Chyba | Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life[END_REF][START_REF] Lowe | The terrestrial record of Late Heavy Bombardment[END_REF][START_REF] Maurette | Carbonaceous Micrometeorites and the Origin of Life[END_REF][START_REF] Westall | Biosignatures on Mars: What, Where, and How? Implications for the Search for Martian Life[END_REF]. Therefore, the amount of carbon present on the surface of Mars, due to the contribution of exogenous sources, would be underestimated. The survival potential of this delivered organic matter is explored in Section I.2.3.2.

Micrometeorites and IDPs

Micrometeorites generally have a carbon content of between 0.2 and 2.8% by mass [START_REF] Matrajt | A nuclear microprobe study of the distribution and concentration of carbon and nitrogen in Murchison and Tagish Lake meteorites, Antarctic micrometeorites, and IDPs: Implications for astrobiology[END_REF][START_REF] Maurette | Accretion of neon, organics, CO2, nitrogen and water from large interplanetary dust particles on the early Earth[END_REF] and up to between 35 and 55% by mass for some ultra-carbon Antarctic micrometeorites (UCAMM) [START_REF] Dobrică | Raman characterization of carbonaceous matter in CONCORDIA Antarctic micrometeorites[END_REF]. Micrometeorites contain organic matter in an insoluble and soluble phase. Soluble organic matter is present mainly in the form of PAHs such as chrysene, pyrene, phenanthrene or tetramethylphenanthrene [START_REF] Clemett | Observation of Indigenous Polycyclic Aromatic Hydrocarbons in 'Giant' carbonaceous Antarctic Micrometeorites[END_REF]) at abundances similar to those found in the Murchison meteorite [START_REF] Maurette | Carbonaceous Micrometeorites and the Origin of Life[END_REF]. Amino acids are also present in micrometeorites, the most abundant of which are α-aminoisobutyric acid (AIB) and alanine detected in a racemic mixture [START_REF] Brinton | A Search for Extraterrestrial Amino Acids in Carbonaceous Antarctic Micrometeorites[END_REF][START_REF] Maurette | Carbonaceous Micrometeorites and the Origin of Life[END_REF]. IDPs are also rich in organic molecules, with a carbon content of around 12% by mass, which can sometimes represent up to 90% of the total volume of IDPs [START_REF] Flynn | Physical properties of meteorites and interplanetary dust particles: clues to the properties of the meteors and their parent bodies[END_REF]). Organic matter is present in the form of globules (<1 μm), films of around 100 nm, or matrix binding minerals [START_REF] Flynn | The origin of organic matter in the solar system: evidence from the interplanetary dust particles[END_REF]. It mainly consists of refractory materials, close to those found in meteorites, such as aromatic structures C=C and PAHs, aliphatic structures (CH2 and CH3), nitriles (C≡N) and carbonyls (C=O) [START_REF] Clemett | Identification of Complex Aromatic Molecules in Individual Interplanetary Dust Particles[END_REF][START_REF] Dobrică | Raman characterization of carbonaceous matter in CONCORDIA Antarctic micrometeorites[END_REF][START_REF] Flynn | Physical properties of meteorites and interplanetary dust particles: clues to the properties of the meteors and their parent bodies[END_REF][START_REF] Matrajt | The origin of the 3.4 µm feature in WILD 2 cometary particles and in ultracarbonaceous interplanetary dust particles[END_REF].

Meteorites

Meteorites are fragments of comets or asteroids, classified into several categories according to their composition and their parent body. The richest in organic materials (around 2.5% by mass) are carbonaceous chondrites (CC) representing 4.6% of meteorites that fall on Earth [START_REF] Geiger | Meteorite Find Locations, Shock Classification, and Pairing of 464 Meteorites from the Sahara and the Mineralogical and Chemical Characterization of Rare Types[END_REF]. Soluble organic matter in meteorites is very diverse. 14,000 compounds have been identified in the Murchison meteorite by ultra-high molecular resolution Fourier transform mass spectrometry. Among these molecules are carboxylic acids, phosphonic and sulfonic acids, amino acids, polycyclic and linear aromatic hydrocarbons, amines and amides, alcohols, aldehydes, ketones, compounds that can lead to the formation of sugars, and nitrogen heterocycles [START_REF] Schmitt-Kopplin | High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall[END_REF].

Martian meteorites which have landed and been collected on Earth are the only samples of the surface of Mars that are available for terrestrial analytical evaluation today. Molecules of astrobiological interest (Section I.1.2) have been detected in meteorites. Although the origins (martian or terrestrial contamination) are still debated, several organic materials have been identified in these meteorites, including PAHs, amino acids, and insoluble macromolecular matter [START_REF] Becker | Fullerenes, fulleranes and polycyclic aromatic hydrocarbons in the Allende meteorite[END_REF][START_REF] Callahan | A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry[END_REF][START_REF] Jull | Isotopic evidence for extraterrestrial organic material in the Martian meteorite, Nakhla[END_REF][START_REF] Sephton | Organic compounds in carbonaceous meteorites[END_REF][START_REF] Steele | Graphite in the martian meteorite Allan Hills 84001[END_REF][START_REF] Wright | Organic matter in a martian meteorite[END_REF]. In the more than 100 amino acids of forms L and D detected in the soluble organic matter of meteorites [START_REF] Pizzarello | The organic composition of carbonaceous meteorites: the evolutionary story ahead of biochemistry[END_REF], around twenty are present in the proteins of living organisms [START_REF] Kwok | Complex organics in space from Solar System to distant galaxies[END_REF]. Others are present in the membranes of bacteria such as β-alanine, AIB and sarcosine [START_REF] Burton | Extraterrestrial amino acids identified in metal-rich CH and CB carbonaceous chondrites from Antarctica[END_REF][START_REF] Martins | Extraterrestrial nucleobases in the Murchison meteorite[END_REF]Sephton & Botta 2008). Nitrogen bases such as adenine, guanine, cytosine and thymine, the main constituents of DNA and RNA (Section I.1.2), and isomers of diaminopurine, which is extremely rare on Earth, have also been detected [START_REF] Callahan | Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases[END_REF]. Formaldehyde, leading to the formation of sugars via formose reactions and constituting DNA and RNA, has been detected in the Murchison meteorite [START_REF] Botta | Extraterrestrial Organic Compounds in Meteorites[END_REF]. Following the detections of glycine, alanine, and β-alanine in multiple meteorites (Nakhla, EETA 79001, Roberts Massif, and ALH84001), analyzes of recovery sites in Antarctica were conducted to determine the potential contamination content of organic materials along with their isotopy. The closeness of these results with those of the meteorites, the absence of AIB, a non-protein amino acid but abundant in exogenous sources, and an enantiomeric excess of L-form, suggested a terrestrial origin of the organic molecules; however, it was not possible to exclude an extraterrestrial origin [START_REF] Callahan | A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry[END_REF][START_REF] Glavin | Amino acids in the Martian meteorite Nakhla[END_REF][START_REF] Jull | Isotopic evidence for extraterrestrial organic material in the Martian meteorite, Nakhla[END_REF][START_REF] Mcdonald | A search for endogenous amino acids in the Martian meteorite EETA79001[END_REF]. The absence of the detection of nitrogen bases and protein amino acids within the Roberts Massif meteorite by [START_REF] Callahan | A search for amino acids and nucleobases in the Martian meteorite Roberts Massif 04262 using liquid chromatography-mass spectrometry[END_REF] could indicate that it was not contaminated.

Among the molecules detected in meteorites, a large number of them are of prebiotic interest and may have contributed to the supply of organic matter to Earth and to the emergence of life. As discussed in Section I.1.2, organic molecules display attributes or patterns indicative of biology, but it can still be challenging to distinguish between biotic origins for these molecular qualities since some have been observed in abiotic sources such as meteorites. For example, a slight excess of L-amino acids has been observed in meteorites (e.g., Murchison) [START_REF] Aponte | Assessing the origins of aliphatic amines in the Murchison meteorite from their compound-specific carbon isotopic ratios and enantiomeric composition[END_REF][START_REF] Cronin | Enantiomeric excesses in meteoritic amino acids[END_REF] and results have shown a strong enantiomeric excess in CCs rich in ammonia [START_REF] Pizzarello | Enantiomeric excesses of chiral amines in ammonia-rich carbonaceous meteorites[END_REF]. If Mars was formed from objects rich in volatile materials [START_REF] Brasser | Oort cloud and Scattered Disc formation during a late dynamical instability in the Solar System[END_REF], the probability that it has at the same time increased its supply of organic molecules (due to exogenous deposit) is important. During the crystallization of magma, carbon can be precipitated into organic molecules. Organic molecules of different chemical families, detected in several martian meteorites, are potential evidence of this synthetic route [START_REF] Steele | Graphite in the martian meteorite Allan Hills 84001[END_REF].

Comets

Comets are among the most primitive objects and witnesses of the formation of the solar system (4.6 Ga). These bodies are made up of rocks and ice rich in volatile and complex organic compounds. Remote observations of cometary atmospheres have highlighted the presence of more than 25 volatile compounds including organic molecules such as CH4, C2H2, C2H6, CH3OH, H2CO, HCOOH, CH3CHO, NH2CO (Bockelée-Morvan 2011) produced in a comet coma during the degradation of dust grains [START_REF] Mumma | The Chemical Composition of Comets-Emerging Taxonomies and Natal Heritage[END_REF]. In situ analyzes of the chemical composition of cometary grains [START_REF] Brownlee | Comet 81P/Wild 2 Under a Microscope[END_REF][START_REF] Fomenkova | On the Organic Refractory Component of Cometary Dust[END_REF]) have revealed the presence of complex organic matter of up to 50% by mass [START_REF] Kissel | The organic component in dust from comet Halley as measured by the PUMA mass spectrometer on board Vega 1[END_REF][START_REF] Kissel | Composition of comet Halley dust particles from Vega observations[END_REF]) and between 1 and 37% by mass of carbon with PAHs such as naphthalene, phenanthrene and pyrene [START_REF] Sandford | Organics Captured from Comet 81P/Wild 2 by the Stardust Spacecraft[END_REF][START_REF] Sandford | Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2[END_REF], two amines, methylamine and ethylamine [START_REF] Glavin | Detection of cometary amines in samples returned by Stardust[END_REF], and glycine, an amino acid [START_REF] Elsila | Cometary glycine detected in samples returned by Stardust[END_REF]. Some of the complex organic compounds could not be identified, but their chemical composition would be similar to the IOM of CC. These complex organic compounds would include several chemical groups such as aromatic rings, aliphatic groups, carboxyls, alcohols, nitriles and amides [START_REF] Sandford | Organics Captured from Comet 81P/Wild 2 by the Stardust Spacecraft[END_REF]). However, the discovery of these organic materials was controversial, due to a question of deconvoluting terrestrial from extraterrestrial organics and due to potential alteration of the grains during the analysis [START_REF] De Gregorio | Correlated microanalysis of cometary organic grains returned by Stardust[END_REF][START_REF] Sandford | Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2[END_REF].

Remote sensing measurements of the surface of a cometary nucleus showed the presence of aromatic and aliphatic CH bonds, and of OH bonds compatible with carboxylic groups, or alcohols integrated in a solid macromolecular organic matrix [START_REF] Capaccioni | The organic-rich surface of comet 67P/Churyumov-Gerasimenko as seen by VIRTIS/Rosetta[END_REF]. The chemical groups are thought to come mainly from carboxylic acids [START_REF] Quirico | Refractory and semi-volatile organics at the surface of comet 67P/Churyumov-Gerasimenko: Insights from the VIRTIS/Rosetta imaging spectrometer[END_REF]. In situ measurements of the same cometary nucleus showed the presence of organic molecules previously observed in the coma of other comets and molecules that had never been previously detected in comets or in IDPs [START_REF] Flynn | Comparison of Organic Matter in Comets Churyumov-Gerasimenko and Wild 2 and in IDPs[END_REF][START_REF] Goesmann | Organic compounds on comet 67P/Churyumov-Gerasimenko revealed by COSAC mass spectrometry[END_REF]. Glycine was once again detected as well as phosphorus [START_REF] Altwegg | Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov-Gerasimenko[END_REF]. Some of these molecules are indeed of interest for prebiotic chemistry (Section I.1.2). For example, phosphorus is used by cell membranes.

Laboratory experiments which simulate cometary atmospheres also improve our understanding of the chemical composition of the cometary nucleus. Organic molecules detected in these experiments include hydrocarbons, amides, amines, aldehydes, ketones, carboxylic acids, aromatic compounds, alcohols, amino acids, esters, ethers [START_REF] Cottin | Cometary organic chemistry: a review from observations, numerical and experimental simulations[END_REF], and macromolecules [START_REF] Cottin | Distributed Sources in Comets[END_REF]. The irradiation of interstellar ice analogs with UV radiation during laboratory experiments has demonstrated the detection of amino acids in formed residues [START_REF] Caro | Amino acids from ultraviolet irradiation of interstellar ice analogues[END_REF]. When UV radiation is polarized, it would also be possible to produce these amino acids in L-enantiomeric excess, which could partially explain the asymmetry of living molecules [START_REF] Modica | Enantiomeric excesses induced in amino acids by ultraviolet circularly polarized light irradiation of extraterrestrial ice analogs: a possible source of asymmetry for prebiotic chemistry[END_REF]).

Asteroids

Asteroids have not yet been studied in situ, so current compositional data is from remote sensing. The low surface albedo and red coloring of some asteroids suggests the presence of complex organic molecules such as carbon macromolecules [START_REF] Gradie | The composition of the Trojan asteroids[END_REF]. This hypothesis would be confirmed by the presence of an absorption band in the infrared range at 3.4 μm, representative of aromatic and aliphatic organic compounds [START_REF] Campins | The Origin of Asteroid 101955 (1999 RQ 36 )[END_REF][START_REF] Licandro | 65) Cybele: detection of small silicate grains, water-ice, and organics[END_REF]. Tholins have also been proposed as organic molecules potentially present in asteroids and which could also explain the red coloring of some asteroids [START_REF] Cruikshank | Tholins as coloring agents on outer Solar System bodies[END_REF][START_REF] Sagan | Tholins: organic chemistry of interstellar grains and gas[END_REF]. However, analysis of the samples returned from the Itabawa asteroid by the Hayabusa mission did not reveal the presence of organic compounds native to the asteroid (Naraoka et al. 2015). The NASA Osiris-Rex and the Japan Aerospace Exploration Agency (JAXA) Hayabusa 2 missions are current ongoing asteroid study and sample return missions, expected to return asteroid samples to Earth by the end of 2023 and 2020, respectively, and which will provide the ability to conduct organic inventories of asteroids in the laboratory [START_REF] Kitazato | The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy[END_REF][START_REF] Lauretta | OSIRIS-REx: Sample Return from Asteroid (101955) Bennu[END_REF][START_REF] Watanabe | Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu-A spinning topshaped rubble pile[END_REF].

I.2.3.1.2. Potential indigenous sources of organic matter on Mars

In addition to the contribution of organic molecules by exogenous sources, organic molecules could be synthesized directly on Mars by various endogenous processes, including within the atmosphere, hydrothermal sources, or magma sources. These processes are abiotic generators of organic materials aided by thermal activators. It is also possible that organic molecules were present on Mars from biotic sources at some point in its geologic history or potentially in the subsurface environment today.

Atmospheric syntheses

Organic molecules can be abiotically synthesized in a reducing atmosphere in the presence of liquid water and an energy source [START_REF] Chyba | Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life[END_REF][START_REF] Miller | A Production of Amino Acids Under Possible Primitive Earth Conditions[END_REF][START_REF] Miller | Organic Compound Synthesis on the Primitive Earth[END_REF][START_REF] Takahashi | Photochemical abiotic synthesis of amino-acid precursors from simulated planetary atmospheres by vacuum ultraviolet light[END_REF]. [START_REF] Jiang | Abiotic synthesis of amino acids and self-crystallization under prebiotic conditions[END_REF] showed the possibility of spontaneously forming chiral molecules, a feature of prebiotic chemistry on Earth (Section I.1.2). Simple and complex organic molecules are produced from the reaction as a result of the energy source, some of which are the building blocks of living organisms (Section I.1.2), including amino acids, carboxylic acids, nitriles, alkenes, and nitrogen bases. The scientific community does not agree on the specific reducing or oxidizing properties of the atmospheric composition of early Earth that was necessary for the emergence of prebiotic chemistry. For example, some favor an atmosphere that reduces CO2 and N2 [START_REF] Shaw | Earth's atmosphere -Hadean to early Proterozoic[END_REF], while others support an atmosphere composed mainly of H2 from the protosolar nebula sufficiently rich to allow the production of organic matter [START_REF] Chyba | Rethinking Earth's Early Atmosphere[END_REF]Tian et al. 2005;[START_REF] Wordsworth | Hydrogen-Nitrogen Greenhouse Warming in Earth's Early Atmosphere[END_REF].

Mars likely had an atmosphere composed mainly of H2 and reduced gases during its pre-Noachian period, which was then replaced by a CO2 and H2O neutral atmosphere during the Noachian period, which gradually disappeared during the Hesperian and Amazonian [START_REF] Lammer | Outgassing History and Escape of the Martian Atmosphere and Water Inventory[END_REF]. Under these conditions, only sulfur compounds (H2S or SO2), assumed to be present at the end of the Noachian and in the Hesperian, would still contribute to the synthesis of organic molecules in the atmosphere. [START_REF] Parker | Primordial synthesis of amines and amino acids in a 1958 Miller H<sub>2</sub>S-rich spark discharge experiment[END_REF] demonstrated a significant rate of production of amino acids, amines, and sulfur-containing organic compounds from a mixture of CH4, NH3 and H2O, to which H2S was added. Since the Amazonian period, the martian atmosphere has been mainly oxidizing and is composed of up to 96% CO2, which is unfavorable to the synthesis of organic matter. However, certain molecules made up of one to two carbon atoms like formic acid (HCOOH), can be produced in the presence of water, by reactions of reduction of carbon monoxide (CO) adsorbed on mineral surfaces [START_REF] Hubbard | Photocatalytic Production of Organic Compounds from CO and H<sub>2</sub>O in a Simulated Martian Atmosphere[END_REF][START_REF] Hubbard | Photocatalytic synthesis of organic compounds from CO and water: Involvement of surfaces in the formation and stabilization of products[END_REF]. More recent results which suggest small seasonal variations of methane in the Mars atmosphere [START_REF] Formisano | Detection of Methane in the Atmosphere of Mars[END_REF][START_REF] Mumma | Strong Release of Methane on Mars in Northern Summer 2003[END_REF][START_REF] Webster | Background levels of methane in Mars' atmosphere show strong seasonal variations[END_REF]) are currently a topic of debate within the planetary community. If methane was present in the martian atmosphere in large quantities in the past, it could have been an early source for the production of organic materials.

Hydrothermal sources

The synthesis of organic molecules is possible on Earth in reducing environments such as at the interface between seawater and ultramafic and magmatic rocks at the oceanic crust, known as hydrothermal vents. These sources are rich in volatile compounds (CO2, H2, and H2S) which, when subjected to high pressure and temperature, can produce CH4, hydrocarbons and fatty acids through a collection of reactions known as the Fischer-Tropsch process (Miller et al. 2016a;[START_REF] Sherwood Lollar | Hydrogeologic Controls on Episodic H2 Release from Precambrian Fractured Rocks-Energy for Deep Subsurface Life on Earth and Mars[END_REF]). The following reaction shows the production of hydrocarbons and fatty acids according to the Fischer-Tropsch reactions.

n CO2 (aq) + (3n + 1) H2 à CnH2n+2 + 2n H2O

An additional indication of hydrothermal environments on Earth is the formation of a hydrated mineral called serpentine, which is formed through the reduction of Fe2+ in peridotite rock, through which H2 is produced and Fe2+ is oxidized to Fe3 and Fe3O4 [START_REF] Konn | Hydrocarbons and oxidized organic compounds in hydrothermal fluids from Rainbow and Lost City ultramafic-hosted vents[END_REF]) through the following reaction. Several methods used to determine the type of organic molecules produced in hydrothermal vents have shown the production of mostly branched linear hydrocarbons (C7-C29), monocyclic aromatic hydrocarbons (C7-C8; toluene and styrene), PAHs (C10-C16; naphthalene to pyrene) [START_REF] Charlou | Geochemistry of high H2 and CH4 vent fluids issuing from ultramafic rocks at the Rainbow hydrothermal field (36°14′N, MAR)[END_REF][START_REF] Holm | Initial indications of abiotic formation of hydrocarbons in the Rainbow ultramafic hydrothermal system, Mid-Atlantic Ridge[END_REF][START_REF] Konn | Hydrocarbons and oxidized organic compounds in hydrothermal fluids from Rainbow and Lost City ultramafic-hosted vents[END_REF], carboxylic acids (C9-C18), long chain aliphatic alcohols [START_REF] Konn | Hydrocarbons and oxidized organic compounds in hydrothermal fluids from Rainbow and Lost City ultramafic-hosted vents[END_REF][START_REF] Lang | Elevated concentrations of formate, acetate and dissolved organic carbon found at the Lost City hydrothermal field[END_REF][START_REF] Mccollom | Serpentinites, Hydrogen, and Life[END_REF], and amino acids, amines, and nitrogen bases [START_REF] Hennet | Abiotic synthesis of amino acids under hydrothermal conditions and the origin of life: A perpetual phenomenon[END_REF][START_REF] Holm | Hydrothermal Simulation Experiments as a Tool for Studies of the Origin of Life on Earth and Other Terrestrial Planets: A Review[END_REF][START_REF] Mccollom | Serpentinites, Hydrogen, and Life[END_REF]. While the detection of amino acids near hydrothermal vents has been attributed to a biotic origin [START_REF] Horiuchi | Amino acids in water samples from deep sea hydrothermal vents at Suiyo Seamount, Izu-Bonin Arc, Pacific Ocean[END_REF], laboratory experiments have shown that it is possible to form them abiotically [START_REF] Kitadai | Energetics of Amino Acid Synthesis in Alkaline Hydrothermal Environments[END_REF].

Hydrothermal vents could have been induced on Mars by processes such as geothermal flux, volcanism or meteoritic impacts. Also, since hydrothermal activity occurs mainly underground, organic products would be less subjected to the harsh environmental conditions at the martian surface over geologic time scales. In addition to the abiotic synthesis of organic molecules, serpentinization and carbonation are energy sources favorable to the emergence of life and its development [START_REF] Mccollom | Serpentinites, Hydrogen, and Life[END_REF][START_REF] Russell | Serpentinization as a source of energy at the origin of life[END_REF][START_REF] Westall | Biosignatures on Mars: What, Where, and How? Implications for the Search for Martian Life[END_REF]. Minerals produced in hydrothermal environments such as serpentine, carbonates, and other minerals (e.g., smectite) could aid in the preservation of organic molecules. During the Amazonian period, there has been a general cessation of internal geophysical activity. If the synthesis of biotic or abiotic organic molecules is still currently occurring on Mars, it is likely in hydrothermal sources below ground.

Geological and mineralogical evidence on the surface of Mars indicates past hydrothermal activity, including remote sensing detections of serpentine across multiple regions [START_REF] Ehlmann | Geologic setting of serpentine deposits on Mars[END_REF][START_REF] Quantin | Composition and structures of the subsurface in the vicinity of Valles Marineris as revealed by central uplifts of impact craters[END_REF][START_REF] Viviano | Implications for early hydrothermal environments on Mars through the spectral evidence for carbonation and chloritization reactions in the Nili Fossae region[END_REF] as well as the regional [START_REF] Bultel | Deep alteration between Hellas and Isidis Basins[END_REF] and global [START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF]) presence of carbonates. These minerals would be formed by serpentinization and carbonation reactions [START_REF] Chassefière | The fate of early Mars' lost water: The role of serpentinization[END_REF][START_REF] Sephton | On the Origins of Deep Hydrocarbons[END_REF]. Silica has also been deposited by hydrothermal processes in the Gusev crater [START_REF] Ruff | Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars[END_REF][START_REF] Squyres | Detection of Silica-Rich Deposits on Mars[END_REF][START_REF] Yen | Hydrothermal processes at Gusev Crater: An evaluation of Paso Robles class soils[END_REF]. Ferromagnesian smectites, the most abundant clays on the surface of Mars, would be produced by hydrothermal alteration [START_REF] Carter | Widespread surface weathering on early Mars: A case for a warmer and wetter climate[END_REF][START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF].

Carbonates and clays have also been identified in meteoritic impacts, indicating that these materials are present in the martian subsurface, are excavated during impacts, and provide trace evidence of past hydrothermal activity on Mars [START_REF] Michalski | Groundwater activity on Mars and implications for a deep biosphere[END_REF][START_REF] Michalski | Deep crustal carbonate rocks exposed by meteor impact on Mars[END_REF].

Meteorite impacts can also release energy in the form of heat, creating crustal cracks and producing local hydrothermal activity conducive to a microcosm for the sheltering of life [START_REF] Abramov | Thermal effects of impact bombardments on Noachian Mars[END_REF][START_REF] Marzo | Evidence for Hesperian impact-induced hydrothermalism on Mars[END_REF][START_REF] Osinski | Impact-generated hydrothermal systems on Earth and Mars[END_REF][START_REF] Rathbun | Hydrothermal Systems Associated with Martian Impact Craters[END_REF]. Serpentine and siderite have also been detected in martian meteorites and suggest low temperature hydrothermal activity [START_REF] Bridges | Chapter 5 -Carbonates on Mars[END_REF][START_REF] Hicks | Ferric saponite and serpentine in the nakhlite martian meteorites[END_REF]. The mineralogy of the surface of Mars is linked to aqueous alteration, evidenced by phyllosilicates and carbonates, and is summarized in the review by [START_REF] Ehlmann | Mineralogy of the Martian Surface[END_REF]. Aqueous alternation is further discussed in Section I.2.3.2 in the context of preservation of organic matter by certain minerals.

Magmatic syntheses

Carbon synthesis of abiotic origin may have occurred during the crystallization of martian magma. Macromolecular carbon (MMC) has been detected in martian meteorites in the form of PAHs present as inclusions in magmatic minerals such as olivine and pyroxene. Martian magma promotes the precipitation of reduced carbon during its crystallization [START_REF] Steele | Graphite in the martian meteorite Allan Hills 84001[END_REF]. Chemical thermodynamics models have shown PAHs and linear hydrocarbons such as alkanes formed when magma rich in CO, CO2, and H2 is cooled [START_REF] Zolotov | Abiotic synthesis of polycyclic aromatic hydrocarbons on Mars[END_REF], which offers a hypothesis for the presence of PAHs in the martian meteorite ALH 84001 [START_REF] Mckay | Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001[END_REF][START_REF] Zolotov | Abiotic synthesis of polycyclic aromatic hydrocarbons on Mars[END_REF].

Biosynthesis

On Earth, life itself is the main source of organic molecules. As discussed in Section I.1.2, terrestrial living organisms are composed of basic building blocks in the form of proteins, nucleic acids, and polysaccharides. Living things are also capable of producing organic polymers such as polysaccharides and proteins, the main constituents of extracellular polymers. The earliest organisms on primitive Earth are believed to have formed from the building blocks of abiotically formed organic molecules. The emergence of life is chronologically compatible with the resistance of polypeptides and nucleic acids under the favorable physicochemical conditions of primitive Earth [START_REF] Gargaud | LA VIE: LA QUÊTE DES ORIGINES: BELIN : POUR LA SCIENCE[END_REF]). On Earth, the classification of life which emerges depends on the energy source and the carbon source which sustains the metabolism of the organism. For example, autotrophs use mineral inorganic molecules to synthesize their own organic constituents, phototrophs produce organic matter from CO2, and chemoautotrophs produce organic molecules by drawing energy from redox reactions involving organic and inorganic compounds. The hypothesis of an origin of life from chemoautotrophs from the ocean floor [START_REF] Martin | Hydrothermal vents and the origin of life[END_REF][START_REF] Sojo | The Origin of Life in Alkaline Hydrothermal Vents[END_REF]) is supported by chemical thermodynamic models [START_REF] Holm | Hydrothermal Simulation Experiments as a Tool for Studies of the Origin of Life on Earth and Other Terrestrial Planets: A Review[END_REF][START_REF] Martin | On the origin of biochemistry at an alkaline hydrothermal vent[END_REF]. If life appeared on Earth in hydrothermal vent environments, it also could have appeared at the bottom of putative martian oceans in the form of chemoautotrophic organisms in a hydrothermal environment [START_REF] Michalski | Groundwater activity on Mars and implications for a deep biosphere[END_REF][START_REF] Summons | Preservation of Martian Organic and Environmental Records: Final Report of the Mars Biosignature Working Group[END_REF][START_REF] Westall | Biosignatures on Mars: What, Where, and How? Implications for the Search for Martian Life[END_REF].

I.2.3.2. Preservation potential and evolution of organic matter on the surface of Mars

Despite possible exogenous and endogenous sources of organic matter on Mars, only trace levels have been detected at the martian surface (Section I.3). Therefore, it is critical to understand both potential destructive and preservative forces acting on organic matter at the martian surface. The following paragraphs explore the main processes for destruction and preservation of organic matter under martian environmental conditions. Destructive forces include energetic particles, cosmic rays and ultraviolet radiation as well as oxidation processes. The preservation power of organics in certain minerals is also discussed.

I.2.3.2.1. Solar energetic particles (SEP) and galactic cosmic rays (GCR)

SEP and GCR continuously irradiate the surface of Mars due to the long-term tenuous atmosphere and lack of magnetosphere of the planet. The energy flux on the surface of Mars and the penetration depth by these particles has been determined from numerical models [START_REF] Banerjee | Simulation of the cosmic-ray induced dose-rate within a Martian soil profile[END_REF][START_REF] Mckenna-Lawlor | Overview of energetic particle hazards during prospective manned missions to Mars[END_REF][START_REF] Morthekai | Modelling of the dose-rate variations with depth in the Martian regolith using GEANT4[END_REF][START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF]. Secondary particles would penetrate the martian regolith to a depth of 5 m, below which their flux would be attenuated to 98%. The flux would reach its maximum in the top 40 cm of the surface [START_REF] Banerjee | Simulation of the cosmic-ray induced dose-rate within a Martian soil profile[END_REF][START_REF] Morthekai | Modelling of the dose-rate variations with depth in the Martian regolith using GEANT4[END_REF]. Experimental data by [START_REF] Kminek | The effect of ionizing radiation on the preservation of amino acids on Mars[END_REF] allowed [START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF] to construct a model estimating the effect of SEP and GCR on organic matter from the surface up to a depth of 5 cm. On the surface, small molecules (on the order of 100 u), would resist for about 100 million years and in the subsurface (buried under 4-5 cm of rock) for a billion years, while more complex molecules (>500 amu) would be degraded up to ten times faster. The energy and flux of these particles has also been recently measured in situ using the Radiation Assessment Detector (RAD) instrument on board the Curiosity rover and these measurements are consistent with the orders of magnitude estimated by numerical models [START_REF] Ehresmann | Charged particle spectra obtained with the Mars Science Laboratory Radiation Assessment Detector (MSL/RAD) on the surface of Mars[END_REF][START_REF] Guo | Modeling the variations of dose rate measured by RAD during the first martian year: 2012-2014[END_REF][START_REF] Hassler | Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover[END_REF].

It is possible that the denser primitive atmosphere of Mars allowed for a flux of up to 2 to 3 orders of magnitude below that of today [START_REF] Molina-Cuberos | Cosmic Ray and UV Radiation Models on the Ancient Martian Surface[END_REF]. The evolution of the flow of energetic particles with the density of the martian atmosphere has implications for the intensity of this energy at the martian surface over geologic times and the potential for destruction of organic molecules essential to the emergence of life in Mars's history [START_REF] Lammer | Exposure of the ancient Martian surface to extraterrestrial radiation and its implication for molecules essential for life[END_REF]). These particles can directly collide with molecules or interact with the atmosphere and the soil, producing reactive chemical species (radicals, oxychlorinated mineral phases) that can oxidize organic matter [START_REF] Court | The alteration of organic matter in response to ionising irradiation: Chemical trends and implications for extraterrestrial sample analysis[END_REF][START_REF] Court | Raman spectroscopy of irradiated organic matter[END_REF][START_REF] Gerakines | In situ measurements of the radiation stability of amino acids at 15-140K[END_REF][START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF]. Irradiation by gamma rays of organic molecules has been studied in the laboratory and has shown fragmentation of macromolecules, e.g., CO2 and amines from decarboxylation of amino acids [START_REF] Gerakines | Glycine's Radiolytic Destruction in Ices: First in situ Laboratory Measurements for Mars[END_REF][START_REF] Gerakines | In situ measurements of the radiation stability of amino acids at 15-140K[END_REF][START_REF] Kminek | The effect of ionizing radiation on the preservation of amino acids on Mars[END_REF]). It should be noted that irradiation may not always have a destructive effect, since it has been shown that irradiation of glycine by protons (~1 MeV) causes the formation of peptide bonds [START_REF] Pilling | The Influence of Crystallinity Degree on the Glycine Decomposition Induced by 1 MeV Proton Bombardment in Space Analog Conditions[END_REF]. SEP and GCR can therefore modify organic molecules, erase their traces, and even modify bioindicators such as isotopic composition over geologic time scales [START_REF] Pavlov | Homochirality Origin in Nature: Possible Versions[END_REF].

I.2.3.2.2. Ultraviolet radiation

Radiative transfer models based on atmospheric compositional data have predicted that photons with wavelengths less than 190 nm cannot reach the martian surface because they are absorbed by CO2 in the atmosphere [START_REF] Cockell | The Ultraviolet Environment of Mars: Biological Implications Past, Present, and Future[END_REF][START_REF] Kuhn | Ammonia photolysis and the greenhouse effect in the primordial atmosphere of the earth[END_REF][START_REF] Patel | Annual solar UV exposure and biological effective dose rates on the Martian surface[END_REF][START_REF] Rontó | Solar UV Irradiation Conditions on the Surface of Mars ¶[END_REF]. Models which consider the denser atmosphere of Mars's past (1 bar of CO2) predict only photons with wavelengths greater than 220 nm [START_REF] Molina-Cuberos | Cosmic Ray and UV Radiation Models on the Ancient Martian Surface[END_REF] or 230 nm [START_REF] Rontó | Solar UV Irradiation Conditions on the Surface of Mars ¶[END_REF] would reach the martian surface. When secondary species are included in the numerical calculations (O3, O2, NO, NO2), the transmission limit wavelength increases to 290 nm [START_REF] Lammer | Exposure of the ancient Martian surface to extraterrestrial radiation and its implication for molecules essential for life[END_REF][START_REF] Rontó | Solar UV Irradiation Conditions on the Surface of Mars ¶[END_REF]. Measurements by the Rover Environmental Monitoring Station (REMS) instrument aboard the Curiosity rover confirmed the transmission of UV radiation through the current atmosphere above 190 nm wavelength [START_REF] Gómez-Elvira | Curiosity's rover environmental monitoring station: Overview of the first 100 sols[END_REF]. Unlike on Earth where these wavelengths are absorbed by the ozone layer, the surface of Mars would therefore be irradiated by UV photons with wavelengths between 190 and 400 nm (ten Kate et al. 2006).

Some studies have shown that UV radiation would penetrate the rocks of the martian regolith up to around 100 nm, much less than GCR and SEP [START_REF] Keppler | Ultravioletradiation-induced methane emissions from meteorites and the Martian atmosphere[END_REF], though a recent study has proposed that detectable levels of UV radiation can penetrate >500 µm in pressed pellets of natural gypsum, kaolinite, Mars simulant basalt, and welded tuff [START_REF] Carrier | Attenuation of Ultraviolet Radiation in Rocks and Minerals: Implications for Mars Science[END_REF]. UV radiation would be attenuated at a 1 mm depth if the regolith is rich in iron or at a 5 cm depth in pure water ices as might be the case in the martian polar regions [START_REF] Rontó | Solar UV Irradiation Conditions on the Surface of Mars ¶[END_REF]. UV radiation can interact directly with organic molecules at the martian surface and initiate photolysis or reactive intermediate species capable of oxidizing organic molecules. If a molecule is not able to dissipate or store the energy of incident photons without dissociating, photolysis will generally induce a change in the structure of the molecule [START_REF] Oró | The photolytic degradation and oxidation of organic compounds under simulated Martian conditions[END_REF][START_REF] Poch | Chemical evolution of organic molecules under Mars-like UV radiation conditions simulated in the laboratory with the "Mars organic molecule irradiation and evolution" (MOMIE) setup[END_REF][START_REF] Stalport | Investigating the Photostability of Carboxylic Acids Exposed to Mars Surface Ultraviolet Radiation Conditions[END_REF][START_REF] Stalport | The Photochemistry on Space Station (PSS) Experiment: Organic Matter under Mars-like Surface UV Radiation Conditions in Low Earth Orbit[END_REF][START_REF] Ten Kate | The effects of Martian near surface conditions on the photochemistry of amino acids[END_REF].

Laboratory experiments have been conducted on the UV irradiation of organic molecules that could be present at the martian surface in order to understand the potential chemical evolution of these molecules. These experiments have shown that amino acids, PAHs, and organic molecules present in the Murchison meteorite are degraded or are oxidized completely under exposure to UV radiation [START_REF] Oró | The photolytic degradation and oxidation of organic compounds under simulated Martian conditions[END_REF]. Studies have shown that the irradiation of glycine and other small amino acids leads to decomposition into CH4 and volatile hydrocarbons [START_REF] Stoker | Organic degradation under simulated Martian conditions[END_REF][START_REF] Stoker | Degradation of Organic Compounds Under Simulated Martian Conditions[END_REF]. Other studies have shown that despite a burial depth of between 1 and 3 cm, amino acids are photodissociated by UV radiation under martian surface environmental conditions [START_REF] Johnson | Extended survival of several organisms and amino acids under simulated martian surface conditions[END_REF]. Experiments conducted in simulated martian environmental conditions amino acids, aliphatic and aromatic carboxylic acids, PAHs, and nitrogenous and kerogenic bases show fragmentation and/or polymerization under the effect of UV radiation, which leads to the formation of volatile organic molecules (alkanes) or inorganic compounds (CO2, CO and H2O) [START_REF] Dartnell | Destruction of Raman biosignatures by ionising radiation and the implications for life detection on Mars[END_REF][START_REF] Dartnell | Degradation of microbial fluorescence biosignatures by solar ultraviolet radiation on Mars[END_REF][START_REF] Gontareva | Photochemical stability of biomolecules in the experiments modelling Martian surface conditions[END_REF][START_REF] Hintze | Alteration of five organic compounds by glow discharge plasma and UV light under simulated Mars conditions[END_REF][START_REF] Keppler | Ultravioletradiation-induced methane emissions from meteorites and the Martian atmosphere[END_REF][START_REF] Noblet | The PROCESS Experiment: Amino and Carboxylic Acids Under Mars-Like Surface UV Radiation Conditions in Low-Earth Orbit[END_REF][START_REF] Poch | Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions[END_REF][START_REF] Poch | Chemical evolution of organic molecules under Mars-like UV radiation conditions simulated in the laboratory with the "Mars organic molecule irradiation and evolution" (MOMIE) setup[END_REF][START_REF] Schuerger | Methane evolution from UV-irradiated spacecraft materials under simulated martian conditions: Implications for the Mars Science Laboratory (MSL) mission[END_REF][START_REF] Schuerger | Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions[END_REF][START_REF] Stalport | Investigating the Photostability of Carboxylic Acids Exposed to Mars Surface Ultraviolet Radiation Conditions[END_REF][START_REF] Stalport | UVolution, a Photochemistry Experiment in Low Earth Orbit: Investigation of the Photostability of Carboxylic Acids Exposed to Mars Surface UV Radiation Conditions[END_REF]. Polymerization leads to the formation of heavy organic residues such as macromolecules upon the irradiation of adenine and mellitic acid [START_REF] Poch | Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions[END_REF][START_REF] Poch | Chemical evolution of organic molecules under Mars-like UV radiation conditions simulated in the laboratory with the "Mars organic molecule irradiation and evolution" (MOMIE) setup[END_REF]. Biopolymers, such as DNA, RNA and proteins, degrade rapidly under the UV radiation and oxidizing conditions of the martian surface environment [START_REF] Martins | Organic chemistry of carbonaceous chondrites[END_REF].

In summary, organic molecules will degrade or evolve more quickly under UV radiation than due to SEP and GCR. Despite the low energy of UV photons, the higher flux compared to higher energy particles results in the degradation or polymerization of organic materials potentially present at the surface of Mars. On the other hand, certain minerals can have photoprotective properties on organic matter, e.g., nontronite [START_REF] Poch | Effect of Nontronite Smectite Clay on the Chemical Evolution of Several Organic Molecules under Simulated Martian Surface Ultraviolet Radiation Conditions[END_REF]. Simulations in martian environmental conditions also show the preservation of amino acids under UV radiation in smectites and sulfates [START_REF] Dos Santos | Influence of mineralogy on the preservation of amino acids under simulated Mars conditions[END_REF].

I.2.3.2.3. Oxidation processes

Martian rocks have gradually oxidized under the effect of the Amazonian atmosphere, evidenced by a surface composed mainly of iron with 20 to 30% in oxidized form (Fe 3+ ) [START_REF] Mcsween | Determining the modal mineralogy of Martian soils[END_REF]. There are multiple forms of oxidants assumed to be present at the martian surface or which have been detected already on Mars [START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF]. In situ analyzes including those made by Viking 1 and 2 in 1976, Phoenix in 2008, and MSL in 2012 (Section I.3.2) have highlighted the presence of several forms of oxidants in the martian soil. These oxidants can provoke the formation of reactive species which can react with and transform organic matter potentially present in the martian soil. This section explores types of oxidants, including hydrogen peroxide (H2O2), metal oxides such as iron-bearing species, and perchlorate and chlorate salts [START_REF] Klein | The Viking biological experiments on Mars[END_REF][START_REF] Klein | The Viking mission and the search for life on Mars[END_REF][START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF]Zent & McKay 1994) and by what processes they can react with martian organic molecules. Table 1 shows oxidants which have been detected or suggested to be present on Mars from a review by [START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF].

Hydrogen Peroxide

Hydrogen peroxide can form either in the atmosphere or regolith [START_REF] Bullock | A Coupled Soil-Atmosphere Model of H2O2 on Mars[END_REF][START_REF] Chyba | Depth to Unoxidized Material in the Martian Regolith[END_REF][START_REF] Hartman | Oxygenic photosynthesis and the oxidation state of Mars[END_REF][START_REF] Hunten | Possible oxidant sources in the atmosphere and surface of Mars[END_REF][START_REF] Zent | On the thickness of the oxidized layer of the Martian regolith[END_REF]. The presence of hydrogen peroxide (H2O2) in the martian atmosphere and its seasonal variations have been measured, mapped, and modeled [START_REF] Clancy | A measurement of the 362 GHz absorption line of Mars atmospheric H2O2[END_REF][START_REF] Encrenaz | Hydrogen peroxide on Mars: evidence for spatial and seasonal variations[END_REF][START_REF] Encrenaz | Hydrogen peroxide on Mars: Observations, interpretation and future plans[END_REF][START_REF] Encrenaz | Seasonal variations of hydrogen peroxide and water vapor on Mars: Further indications of heterogeneous chemistry[END_REF]. The formation of H2O2 begins in the upper martian atmosphere when water molecules are photolysed by UV photons, after which radicals ( • H and • OH) react with CO, CO2 and O2 to form the peroxide radical ( • HO2) which self-reacts to produce H2O2, which can disperse through the atmosphere [START_REF] Encrenaz | Hydrogen peroxide on Mars: Observations, interpretation and future plans[END_REF].

At the surface, H2O2 can penetrate the regolith by diffusion and adsorb on minerals. Models predict a depth by diffusion of between a few centimeters and a few hundred meters [START_REF] Bullock | A Coupled Soil-Atmosphere Model of H2O2 on Mars[END_REF][START_REF] Chyba | Depth to Unoxidized Material in the Martian Regolith[END_REF][START_REF] Davila | Subsurface formation of oxidants on Mars and implications for the preservation of organic biosignatures[END_REF][START_REF] Hartman | Oxygenic photosynthesis and the oxidation state of Mars[END_REF][START_REF] Zent | On the thickness of the oxidized layer of the Martian regolith[END_REF]) though data provided by spectroscopy from the Spirit, Opportunity and Curiosity rovers, suggest the mineral layer would only be oxidized over a few millimeters of thickness of regolith and basaltic rocks [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF]. H2O2 can also be produced by interaction between the regolith and liquid water present on the surface of minerals such as olivine, pyroxene or pyrite [START_REF] Borda | Pyrite-Induced Hydrogen Peroxide Formation as a Driving Force in the Evolution of Photosynthetic Organisms on an Early Earth[END_REF][START_REF] Davila | Subsurface formation of oxidants on Mars and implications for the preservation of organic biosignatures[END_REF][START_REF] Huguenin | Chemical weathering and the Viking Biology Experiments on Mars[END_REF][START_REF] Huguenin | Frost-weathering on Mars: Experimental evidence for peroxide formation[END_REF][START_REF] Hurowitz | Production of hydrogen peroxide in Martian and lunar soils[END_REF] or diffuse deeply during electrically charged dust storms [START_REF] Atreya | Oxidant Enhancement in Martian Dust Devils and Storms: Implications for Life and Habitability[END_REF][START_REF] Delory | Oxidant Enhancement in Martian Dust Devils and Storms: Storm Electric Fields and Electron Dissociative Attachment[END_REF], where it is the product of reactions between CO2 and water present on the surface.

H2O2 will decompose to • OH when exposed to UV radiation or by photodissociation either in the presence of water and iron [START_REF] Walling | Kinetics of the Decomposition of Hydrogen Peroxide Catalyzed by Ferric Ethylenediaminetetraacetate Complex[END_REF]. The • OH radical is a powerful oxidizing species capable of reacting with organic molecules potentially present in the regolith and producing carboxylic acids (e.g., mellitic acid) from the oxidation of PAHs or kerogens [START_REF] Benner | The missing organic molecules on Mars[END_REF]. In the laboratory, degradation of amino acids under UV radiation was shown to be accentuated by the presence of trace water vapor [START_REF] Garry | Analysis and survival of amino acids in Martian regolith analogs[END_REF]). However, the influence of water on the photodissociation of organic molecules could not be confirmed by laboratory experiments carried out on pure organic matter [START_REF] Ten Kate | The effects of Martian near surface conditions on the photochemistry of amino acids[END_REF]), which can be negligible at wavelengths reaching the Martian surface (λ>190 nm) [START_REF] Parkinson | Absorption cross-section measurements of water vapor in the wavelength region 181-199 nm[END_REF]. The observed oxidation of the martian surface cannot be entirely attributed to H2O2 because of its low concentration [START_REF] Atreya | Methane and related trace species on Mars: Origin, loss, implications for life, and habitability[END_REF].

Iron oxides

The martian surface regolith contains high concentrations of iron oxides, about 10-20 wt. %, as evidenced by its famous red color [START_REF] Foley | Final chemical results from the Mars Pathfinder alpha proton X-ray spectrometer[END_REF][START_REF] Rieder | The Chemical Composition of Martian Soil and Rocks Returned by the Mobile Alpha Proton X-ray Spectrometer: Preliminary Results from the X-ray Mode[END_REF]. Hematite (Fe2O3) and goethite (FeOOH) have been identified at the surface of Mars [START_REF] Christensen | Detection of crystalline hematite mineralization on Mars by the Thermal Emission Spectrometer: Evidence for near-surface water[END_REF][START_REF] Christensen | Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover[END_REF]) and in martian meteorites [START_REF] Morris | Mineralogy, composition, and alteration of Mars Pathfinder rocks and soils: Evidence from multispectral, elemental, and magnetic data on terrestrial analogue, SNC meteorite, and Pathfinder samples[END_REF]. Maghemite has not been unambiguously identified in Mars remote sensing data [START_REF] Bell Iii | Mineralogic and compositional properties of Martian soil and dust: Results from Mars Pathfinder[END_REF][START_REF] Mcsween | Chemical, multispectral, and textural constraints on the composition and origin of rocks at the Mars Pathfinder landing site[END_REF][START_REF] Morris | Mineralogy, composition, and alteration of Mars Pathfinder rocks and soils: Evidence from multispectral, elemental, and magnetic data on terrestrial analogue, SNC meteorite, and Pathfinder samples[END_REF]. The weathering of the rocks and the regolith occurred in part during the Amazonian period, under the influence of the CO2-rich atmosphere and high levels of UV radiation [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF]. Hematite (Fe2O3) and maghemite (Fe2O3) are thermodynamically stable in the current martian environment [START_REF] Gooding | Chemical weathering on Mars thermodynamic stabilities of primary minerals (and their alteration products) from mafic igneous rocks[END_REF] and hematite is known to be present at Gale Crater on Mars [START_REF] Fraeman | A hematite-bearing layer in Gale Crater, Mars: Mapping and implications for past aqueous conditions[END_REF]). These oxidized minerals, in conjunction with the effects of UV radiation and by their semi-conductive nature, are capable of catalyzing redox reactions of organic molecules adsorbed to mineral surfaces [START_REF] Quinn | Peroxide-Modified Titanium Dioxide: a Chemical Analog of Putative Martian Soil Oxidants[END_REF].

Iron oxides can also lead to the formation of reactive radical species (e.g., • OH and the superoxide O2 -) by redox reactions if H2O, H2, or H2O2 are adsorbed on the surface of minerals [START_REF] Zent | The formation and stability of the superoxide radical (O2-) on rock-forming minerals: Band gaps, hydroxylation state, and implications for Mars oxidant chemistry[END_REF]. Due to their high reactivity, the • OH radicals and O2 -superoxides act on organic molecules similarly to that described for the case of H2O2 by progressively oxidizing them until their total degradation into final oxidation products [START_REF] Benner | The missing organic molecules on Mars[END_REF][START_REF] Yen | Evidence That the Reactivity of the Martian Soil Is Due to Superoxide Ions[END_REF]. [START_REF] Shkrob | Light Induced Fragmentation of Polyfunctional Carboxylated Compounds on Hydrated Metal Oxide Particles: From Simple Organic Acids to Peptides[END_REF], Shkrob, Chemerisov, &[START_REF] Shkrob | Photocatalytic Decomposition of Carboxylated Molecules on Light-Exposed Martian Regolith and Its Relation to Methane Production on Mars[END_REF][START_REF] Shkrob | Photooxidation of Nucleic Acids on Metal Oxides: Physicochemical and Astrobiological Perspectives[END_REF] conducted laboratory irradiation experiments on iron and titanium oxides such as hematite, goethite, and anatase in order to study the decomposition products induced by these redox reactions. Various types of organic molecules were adsorbed to the minerals, including aliphatic and aromatic carboxylic acids [START_REF] Benner | The missing organic molecules on Mars[END_REF], peptides, amino acids and nucleic acids. These studies found that the organics decompose into CO2 and CH4 and cause the formation of an alkyl radical. Experiments performed with maghemite, hematite, and magnetite in the presence of organics yielded CO2 release. [START_REF] Oyama | A model of Martian surface chemistry[END_REF] proposed a mechanism for the degradation in the liquid phase of organics containing a carboxyl group, in the presence of maghemite and hydrogen peroxide by the formation of a complex between iron oxides and organics, eventually yielding CO2 and H2O.

Perchlorate and chlorate salts

Perchlorate anions (ClO4 -) in association with Mg 2+ , Na + , K + , and Ca 2+ cations were detected by the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) package onboard the Phoenix lander [START_REF] Kounaves | Evidence of martian perchlorate, chlorate, and nitrate in Mars meteorite EETA79001: Implications for oxidants and organics[END_REF]) at average concentrations of 0.4 to 0.6 wt. % [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF]. The presence of perchlorate was confirmed by the Thermal and Evolved Gas Analyzer (TEGA) instrument, also on the Phoenix lander [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF]). Perchlorate has also been detected at Gale Crater by the Sample Analysis at Mars (SAM) instrument on board Curiosity between 0.07 and 1.3% by mass [START_REF] Glavin | Evidence for perchlorates and the origin of chlorinated hydrocarbons detected by SAM at the Rocknest aeolian deposit in Gale Crater[END_REF][START_REF] Leshin | Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover[END_REF]) and the presence of perchlorate has also been inferred at the Viking lander sites [START_REF] Guzman | Identification of Chlorobenzene in the Viking Gas Chromatograph-Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars[END_REF][START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF]. Decomposition of perchlorate and chlorate salts could explain the detection of O2 and HCl during the Evolved Gas Analysis (EGA) of samples from John Klein and Cumberland samples by SAM [START_REF] Ming | Volatile and Organic Compositions of Sedimentary Rocks in Yellowknife Bay, Gale Crater[END_REF]. It is possible that presence of Mg-perchlorate and then to the formation of perchlorate after reaction with ozone or oxygen atoms. Perchlorate could also form from chlorinated aerosols during electrostatic events [START_REF] Dasgupta | The Origin of Naturally Occurring Perchlorate: The Role of Atmospheric Processes[END_REF], but this hypothesis requires a high number of electrostatic events to explain the ClO4 -:Cl -ratio measured by Phoenix [START_REF] Catling | Atmospheric origins of perchlorate on Mars and in the Atacama[END_REF]. Reactions on the surface of metal oxides have also been proposed in which the irradiation by UV radiation would oxidize chloride ions present on the surface to form perchlorate [START_REF] Schuttlefield | Photooxidation of Chloride by Oxide Minerals: Implications for Perchlorate on Mars[END_REF]. Laboratory studies have demonstrated the formation of perchlorate and chlorate ions from UV irradiation of NaCl in regolith samples composed of Fe2O3, Al2O3, TiO2, and SiO2 which were consistent with the ClO4 -:Cl -ratio measured by Phoenix [START_REF] Carrier | The origins of perchlorate in the Martian soil[END_REF]. Perchlorate could also be formed during the irradiation of CO2 ices by SEP and GCR [START_REF] Kim | Radiation-Induced Formation of Chlorine Oxides and Their Potential Role in the Origin of Martian Perchlorates[END_REF].

Table 2: Possible mechanisms to produce perchlorate on Mars or the Atacama Desert from [START_REF] Catling | Atmospheric origins of perchlorate on Mars and in the Atacama[END_REF]. In all cases, the ultimate source of oxidation is atmospheric.

Mechanism

Chlorine source Photochemical reactions with oxidants such as O3

(1) Volcanic HCl (plus CH3Cl for the Atacama) (2) HCl liberated from acid displacement reactions (3) Cl atoms liberated from aerosol chloride Electrostatic discharge

(1) Aerosol or surface soil chlorides (2) Volatile species as above Gas-solid reactions with oxidants Aerosol surfaces or soil chlorides on the ground On Earth, perchlorate sources are localized in water-depleted areas, such as the stratosphere and in arid environments [START_REF] Catling | Atmospheric origins of perchlorate on Mars and in the Atacama[END_REF]. They are thought to be produced in Earth's atmosphere by photochemical reactions between ozone and chlorinated species [START_REF] Bao | Natural Perchlorate Has a Unique Oxygen Isotope Signature[END_REF][START_REF] Catling | Atmospheric origins of perchlorate on Mars and in the Atacama[END_REF]. Perchlorates have been detected in the Antarctic Dry Valleys and in Atacama Desert soils, which have a composition similar to that of Mars's regolith [START_REF] Navarro-González | Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life[END_REF][START_REF] Parker | Perchlorate in the environment: the emerging emphasis on natural occurrence[END_REF], although a perchlorate concentration (0.03 wt. %) [START_REF] Parker | Perchlorate in the environment: the emerging emphasis on natural occurrence[END_REF]) lower than that measured by Phoenix on Mars [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF]. Although terrestrial processes for the formation of perchlorate and perchlorate-containing samples such as those from the Atacama Desert are used for comparison to Mars, several observations suggest that martian and terrestrial perchlorate originates from different processes and the preservation mechanisms of perchlorate on Mars over geologic time is an open question. Perchlorate also seems to represent the major chlorinated species in martian samples at multiple locations which have been sampled in situ on Mars, whereas on Earth is found only as trace species in specific environments, suggesting that Earth has perchlorate decomposition mechanisms that Mars does not have [START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF].

Perchlorate salts are strong oxidants [START_REF] Ming | Combustion of organic molecules by the thermal decomposition of perchlorate salts: Implications for organics at the Mars Phoenix Scout Landing Site[END_REF] and have the potential to oxidize organic molecules during in situ analyses involving heating of samples containing perchlorate (Figure 10). The oxidation kinetics of organics, e.g., amino acids, purines, and pyrimidines [START_REF] Kolb | Oxidation of organic materials with perchlorates: relevance to the chemistry on the Martian surface[END_REF]) by perchlorate is very slow at low temperature; therefore, it is likely that the presence of perchlorate does not cause the degradation of organic molecules under martian environmental conditions [START_REF] Schuerger | Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions[END_REF]. However, several studies [START_REF] Góbi | In situ detection of chlorine dioxide (ClO2) in the radiolysis of perchlorates and implications for the stability of organics om Mars[END_REF][START_REF] Quinn | Perchlorate Radiolysis on Mars and the Origin of Martian Soil Reactivity[END_REF][START_REF] Turner | Mechanistic studies on the radiolytic decomposition of perchlorates on the martian surface[END_REF] have suggested that radiolysis of perchlorate by cosmic I.2.3.2.4. Minerals produced by aqueous alteration and the preservation potential of organics Some evidence for the presence of liquid water at the martian surface across its geologic history resides in the presence of minerals which witnessed the aqueous alteration of rocks, such as phyllosilicates [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF][START_REF] Flahaut | Embedded clays and sulfates in Meridiani Planum[END_REF][START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF]. There is a global distribution on Mars of hydrated minerals and potential reservoirs for storage of organic material which has been mapped by [START_REF] Ehlmann | Mineralogy of the Martian Surface[END_REF] and is shown in Figure 12. Rocks which exhibit evidence of alteration by aqueous processes can be of hydrothermal or sedimentary origin such as is the case for phyllosilicates [START_REF] Summons | Preservation of Martian Organic and Environmental Records: Final Report of the Mars Biosignature Working Group[END_REF]. There is also evidence of past hydrothermal environments on Mars in the form of silica, serpentine, and carbonates [START_REF] Bultel | Deep alteration between Hellas and Isidis Basins[END_REF][START_REF] Ehlmann | Mineralogy of the Martian Surface[END_REF][START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF][START_REF] Squyres | Detection of Silica-Rich Deposits on Mars[END_REF][START_REF] Wray | Orbital evidence for more widespread carbonate-bearing rocks on Mars[END_REF]) (Section I.2.3.1). Magmatic rocks composed during periods of volcanic activity, mainly of pyroxene, olivine, and plagioclase, are also a possible reservoir of organic materials. Deposits of water ice in the form of polar ice caps on the surface or tropical glaciers in the subsurface could also be storage sites for organic materials.

From the analysis of data collected by the Visible and Infrared Mineralogical Mapping Spectrometer, known as OMEGA, [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF] proposed three sequential eras characterized by surface weathering products as listed below and as shown in Figure 11.

(1) Non-acidic aqueous alteration, demonstrated by the presence of phyllosilicates (Phyllosian) (2) Acidic aqueous alteration, demonstrated by the presence of sulfates (Theiikien) (3) Non-aqueous atmospheric alteration, evidenced by the presence of iron oxides [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF].

Iron oxides have already been discussed as potential destructive forces of organic matter in the previous section. The following sections focus on phyllosilicates, carbonates, and sulfates which could serve as preservers of organic matter on Mars. Sedimentary environments in general constitute ideal sites for the conservation of organic molecules, since organics would be rapidly incorporated [START_REF] Hedges | The effect of various clay minerals on the thermal decomposition of stearic acid under 'bulk Flow' conditions[END_REF].

Phyllosilicates and other hydrated silicates

The presence of clays on the surface of Mars has been suggested since the Viking mission [START_REF] Toulmin Iii | Geochemical and mineralogical interpretation of the Viking inorganic chemical results[END_REF]. OMEGA and the Compact Reconnaissance Imaging Spectroscopy Mapping (CRISM) instrument onboard the Mars Express and Mars Reconnaissance Orbiter (MRO) probes have detected hydrated minerals on the surface of Mars. These clays are phyllosilicates and have mainly been identified in the southern hemisphere plateaus [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF][START_REF] Mustard | Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument[END_REF][START_REF] Poulet | Phyllosilicates on Mars and implications for early martian climate[END_REF]. Clays detected by OMEGA are likely nontronite (Fe-rich), montmorillonite (Al-rich), and saponite (Mg-rich) [START_REF] Chevrier | Mineralogy and evolution of the surface of Mars: A review[END_REF].

The presence of clays appears to be limited to ancient terrains [START_REF] Mustard | Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument[END_REF]. Clays have also been identified in large impact craters in the northern plains of Mars [START_REF] Carter | Detection of Hydrated Silicates in Crustal Outcrops in the Northern Plains of Mars[END_REF], suggesting that clays could be widespread over the entire martian surface. Clays could have been formed by various processes of aqueous alteration, either on the surface [START_REF] Ehlmann | Geochemical consequences of widespread clay mineral formation in Mars' ancient crust[END_REF][START_REF] Poulet | Phyllosilicates on Mars and implications for early martian climate[END_REF] or in the subsurface during hydrothermal activities linked to volcanism and impacts [START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF][START_REF] Tornabene | An impact origin for hydrated silicates on Mars: A synthesis[END_REF]. A review by [START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF] suggests significant formation of clays below the martian surface through circulation of hydrothermal groundwater. Conditions from the end of the Hesperian period to the present have been cold and dry, resulting in the cessation of clay formation [START_REF] Ehlmann | Subsurface water and clay mineral formation during the early history of Mars[END_REF]. Aqueous environments that have led to the formation of clays have been detected both under the surface [START_REF] Arvidson | Ancient Aqueous Environments at Endeavour Crater[END_REF][START_REF] Grotzinger | A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater[END_REF]) and at the surface [START_REF] Grotzinger | A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater[END_REF][START_REF] Vaniman | Mineralogy of a Mudstone at Yellowknife Bay, Gale Crater[END_REF]). In addition to clays formed in the presence of liquid water, it is also possible that some were synthesized during the degassing of a magma material rich in water during its solidification [START_REF] Berger | Clay mineral formation on Mars: Chemical constraints and possible contribution of basalt out-gassing[END_REF][START_REF] Meunier | Magmatic precipitation as a possible origin of Noachian clays on Mars[END_REF].

Clays are generally formed by the aqueous alteration of silicate rocks such as basalts. Phyllosilicates have excellent storage and preservation capacity for organic molecules [START_REF] Mortland | Clay-Organic Complexes and Interactions[END_REF]. Their sheet structure gives them a large adsorption surface, both inside (in the interfoliar space) and at the edges, as evidenced by the organic molecules present in phyllosilicates of the terrestrial smectite type in sedimentary basins. Clays may preserve organics from the oxidative conditions of Mars that have been previously discussed, since their high specific area makes their interlayer spaces a favorable location to protect and concentrate organics [START_REF] Kennedy | Mineral Surface Control of Organic Carbon in Black Shale[END_REF]. On Mars, such a favorable environment has been identified by the Mars Reconnaissance Orbiter in a clay-rich fluvial-lacustrine delta in Jezero Crater [START_REF] Ehlmann | Orbital Identification of Carbonate-Bearing Rocks on Mars[END_REF].

Sulfates and carbonates

The transition between the first two eras (Phyllosian and Theiikien) took place early in Mars's history and was characterized by a change from an alkaline, possibly humid environment (favorable for the formation of clays) to an acidic environment (favorable for the formation of sulfates). This change was caused by the significant degassing of volatile species to the martian atmosphere, including sulfur species which were linked to volcanic activity [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF]. Sulfates are synthesized during the increasing acidification of liquid water, caused by the dissolution of sulfur dioxide in water. The appearance of water layers at the surface would have formed sulfate deposits [START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF].

I.3.1. GC-MS instrumentation and the application of wet chemistry

This thesis is focused on the detection and identification of organic molecules potentially preserved in trace states in the martian regolith at the surface or shallow subsurface (1-2 meters depth). Different spectroscopic tools are able to analyze organic matter in condensed samples (e.g., Raman spectroscopy, IR spectroscopy). However, gas chromatography coupled to mass spectrometry (GC-MS) is one of the few techniques for molecular analysis capable of identification of molecular structures while also able to operate under the constraints of the space environment and within the requirements for the space experiment.

I.3.1.1. GC-MS for analysis of planetary surface samples

The selection of gas chromatography coupled to mass spectrometry for in situ analysis of organic molecules on Mars is based on multiple parameters, including its sensitivity and its use in previous space missions. As discussed, organic molecules present on Mars would be diluted in a mineral matrix and would likely be present in trace amounts. Therefore, the analytical tool must be both robust and precise for the qualitative and quantitative analysis of complex mixtures and the identification of molecular constituents. Extraction by solvents, a traditional laboratory technique, is difficult to do with a space experiment due to the problem of conservation of solvents under extreme conditions of pressure and temperature, especially in the case of extractions involving several steps. All components of the experiment must withstand mechanical stress (vibrations linked to takeoff, accelerations, and shocks related to landing) and conditions of the space environment such as vacuum, thermal cycles, and cosmic radiation. The instrument must be conducive to miniaturization and automation and should be compatible with mission mass and energy budgets, which would require analyses that consume the least amount of energy and can be performed preferably in a single step.

Table 3 shows a comparative analysis of GC-MS, High Performance Liquid Chromatography (HPLC), and Capillary Electrophoresis (CE) done by [START_REF] Bada | Detecting amino acids on Mars[END_REF]. GC-MS and HPLC are equally suited for spacecraft instrumentation, while CE is the best prospect for miniaturization. GC-MS becomes an obvious choice based on its proven performance for planetary missions (Section I.3.2) and its long history in Earth-based laboratories for the analysis of astrobiological target compounds such as amino acids. Extremely efficient techniques such as High-Resolution Mass Spectrometry (HRMS) or HPLC have not yet been demonstrated for space, although some are in development for space application [START_REF] Briois | Orbitrap mass analyser for in situ characterisation of planetary environments: Performance evaluation of a laboratory prototype[END_REF].

GC-MS is one of the only in situ molecular analytical techniques which meets all the criteria for the space application. It is also a standard technique that has been used for decades in space missions and benefits from a space heritage guarantying its reliability. The historical use of GC-MS for conducting organic inventories at the martian surface is explored in Section I. In a laboratory setting (Chapters III-V), the GC column is positioned inside an oven (Figure 14) allowing the programming of different temperature sequences. The column is continuously swept by the carrier gas. The carrier gases traditionally used in GC for laboratory experiments are pure hydrogen, helium, nitrogen, or argon, and are regulated by flow or pressure. The laboratory experiments and space experiments described in this thesis use helium as the mobile phase [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF][START_REF] Guzman | Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars[END_REF][START_REF] Mahaffy | The Sample Analysis at Mars Investigation and Instrument Suite[END_REF] with the exception of Chapter II which discusses data from the Viking GC-MS experiments which used hydrogen (H2) as the mobile phase [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. Mixtures of analytes are injected into the column through an injector which is heated beyond the boiling point of the analytes in order to volatilize them, after which they are entrained in the carrier gas flow. The molecules constituting the mixture under analysis have a migration time through the column which is a function of their affinity with the stationary phase, their physicochemical properties and the instrument operating conditions (e.g., temperature, flow rate). This elution time or retention time (RT) is characteristic of each molecule for a given column and given chromatographic conditions. Once arriving at the column outlet after separation, molecules are sent to one or more detectors. Many types of detectors can be coupled to a GC, some of which are very specific to a category of products. The mass spectrometer (MS) is a universally utilized and highly sensitive (up to 10 -18 mol for some of the most recent MS) detector which can be coupled to GC in order to enable strict identification of most detected molecules.

MTBSTFA is a universally used derivatizing reagent, namely sensitive to all compounds possessing acidic hydrogen. It is often used in pretreatment of samples with low volatility intended for GC analysis. The silylation reaction with MTBSTFA has been optimized on standard amino acids by [START_REF] Mackenzie | Analysis of amino acids by gas-liquid chromatography as tert.-butyldimethylsilyl derivatives. Preparation of derivatives in a single reaction[END_REF] showing that the optimal conditions are heating at 75˚C for 30 minutes. MTBSTFA is often used with solvents such as pyridine, acetonitrile, and DMF. For example, DMF is added to MTBSTFA in the laboratory tests described in this thesis not only to play the role of a solvent but DMF can also promote the derivatization reaction as a proton acceptor. DMF is present in the SAM derivatization capsules, which contain 0.5 mL of a 4:1 mixture of MTBSTFA and DMF [START_REF] Mahaffy | The Sample Analysis at Mars Investigation and Instrument Suite[END_REF].

A literature review and discussion of applications of MTBSTFA for space applications and otherwise are further discussed in Chapter V, Section V.1 in the context of perspectives on flightlike laboratory systems for derivatization experiments of natural samples.

I.3.1.2.3. DMF-DMA
It has been demonstrated that the DMF-DMA reaction is largely unaffected by high temperatures (>100˚C), leads to the production of low molecular weight products, and the reaction can be readily automated. DMF-DMA was shown to have significant advantages for space-related applications compared with other reagents [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]. DMF-DMA derivatization preserves the enantiomeric centers of molecules, enabling enantiomeric separation on an enantioselective GC column, which is a feature that MTBSTFA does not enable. DMF-DMA has been utilized in the instrument packages of two space missions, Rosetta-Philae [START_REF] Goesmann | COSAC, the cometary sampling and composition experiment on Philae[END_REF][START_REF] Meierhenrich | Enantiomer separation of hydrocarbons in preparation for ROSETTA's "chiralityexperiment[END_REF]) and ExoMars 2022 [START_REF] Freissinet | Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases[END_REF]. A typical reaction of DMF-DMA on an amino acid is shown in Figure 17, in which it can be seen that in addition to methlylation on the hydroxyl group of the carboxyl functional group of the amino acid, there is also a dimethylformamidination of the amine functional group.

I.3.1.2.4. TMAH
Thermochemolysis combines the heating of the sample to high temperatures (200 to 1000˚C) as in pyrolysis with the chemical derivatization of compounds with labile hydrogen atoms. The extraction and the volatilization by heating to high temperature are accompanied by thermal decomposition of organic compounds and a reaction between acidic functional groups and the alkylating reagent to produce methyl ester and ether groups. The combination of improved extraction of molecules from the mineral matrix with increasing the volatility and decreasing polarity of target compounds make it possible to reduce the temperature of analysis compared to traditional pyrolysis and so to limit the thermal degradation of fragile compounds. Thermochemolysis is a more aggressive chemical treatment than derivatization and targets the most refractory organic matter, enabling detection and identification of carboxylic acids, particularly high molecular weight compounds from lipid membranes, such as fatty acids over 170 Da, as well as other structures released by hydrolysis of biomolecules and geochemically-produced molecules (e.g., carbohydrates, lignins, and amines from peptides and proteins after diagenesis).

The effects of the solvent in which TMAH is diluted (H2O or methanol) on the reaction have been studied by [START_REF] Venema | In-situ hydrolysis/methylation pyrolysis CGC for the characterization of polyaramides[END_REF]. TMAH dissolved in methanol at a ratio of 1:3 is

I.3.2.1.

Viking Landers

The twin 1976 Viking landers (VL-1 and VL-2) performed the first in situ search for organics on the martian surface. Each lander carried a pyrolysis-GC-MS, which was used to search for organics in regolith samples excavated with a robotic arm [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. A total of four samples (two at each landing site) were analyzed, each multiple times, by rapidly heating the sample to one of four temperature steps (50, 200, 350, or 500°C) followed by a 15 s hold, before sweeping the volatilized components into a GC column for separation prior to MS detection. Hydrocarbons and fluorocarbons were detected in all runs and attributed to terrestrial contamination [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. All reported compounds, with the exception of chloromethane detected by VL-1 at levels of 15 parts per billion (ppb) in reference to the mass of the regolith sample; and dichloromethane detected by VL-2 at levels of 2-40 ppb, were identified in in-flight blank runs despite at a lower level. Despite not being identified in the blank runs, the chloromethane and dichloromethane were attributed to either terrestrial contamination resulting from the preflight use of chlorinated cleaning solvents, or from the reaction of absorbed traces of methanol and HCl [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. While [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] did not rule out the possibility that the chloromethane may have been indigenous to the sample, they did not consider the possibility of production of chloromethane in the oven or in the instrument, since they did not know there were oxychlorides in the martian soil.

While today the possibility of chloromethane or chlorobenzene indigenous to the martian soil cannot be excluded, it is unlikely, due to the volatility of these compounds [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] also argued that the detection of chloromethane and dichloromethane in the absence of other related chlorinated compounds suggests a terrestrial origin. A variety of aromatic chlorohydrocarbons, in addition to aliphatic ones, should be produced upon heating of the samples (e.g., [START_REF] Steininger | Influence of magnesium perchlorate on the pyrolysis of organic compounds in Mars analogue soils[END_REF]. [START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF] hypothesized that martian perchlorate (Section I.2.3.2), first detected by the Wet Chemistry Laboratory (WCL) on the 2008 Mars Phoenix lander [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF], could offer an alternative explanation for the presence of chloromethane and dichloromethane in the Viking GC-MS data sets. Pyrolysis-GC-MS experiments using Atacama Desert soils that contained parts per million (ppm) levels of organic carbon, released low levels of chloromethane and dichloromethane when mixed with 1 wt. % magnesium perchlorate after heating to 500°C [START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF]. Based on experimental laboratory results and kinetic models, and the abundance of chloromethane detected by the VL-1 GC-MS, [START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF] suggested that ppm levels of organics indigenous to the martian sample may have provided the carbon source for the reaction of perchlorate in the Viking GC-MS ovens that resulted in the formation of the detected chlorinated organics. This hypothesis for the carbon source plus others which have been explored in the literature or will be explored in this thesis are summarized in Figure 21 in Chapter II. Further discussion and a reanalysis of the Viking GC-MS data is a work included in this thesis in Chapter II.

I.3.2.2. MSL and SAM

The presence of organic carbon in martian surface materials was confirmed by the SAM instrument suite onboard the Curiosity rover. SAM was designed to inventory organic and inorganic volatiles, released upon heating martian samples, using a combination of temperature-dependent evolved gas analysis (EGA) and GC-MS. Despite the presence of high levels of background contamination habitability of Oxia Planum, the landing site selected for the rover, where features and minerals associated with flowing liquid water were observed from the Mars orbit [START_REF] Quantin | Oxia Planum, The Landing Site for ExoMars[END_REF]).

MOMA will have the capability to detect non-statistical distributions of molecules, or molecular patterns of astrobiological interest, with the Laser Desorption/Ionization Mass Spectrometry (LDMS) mode. Laboratory experiments have shown the LDMS mode to be less sensitive to the presence of oxidizing reagents such as perchlorate [START_REF] Li | Detection of Trace Organics in Mars Analog Samples Containing Perchlorate by Laser Desorption/Ionization Mass Spectrometry[END_REF]. MOMA will also have the capability to analyze drilled samples from up to 2 meters in depth. These samples may be protected from the oxidation processes discussed earlier and from solar and galactic radiation over geologic timescales [START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF]. Therefore, they may contain more abundant and pristine organic materials.

MOMA includes a gas chromatographic (GC) package, developed from the experience acquired from the SAM instrument, and an ion trap mass spectrometer (ITMS) [START_REF] Brinckerhoff | Mars Organic Molecule Analyzer (MOMA) mass spectrometer for ExoMars 2018 and beyond[END_REF]).

The GC-MS will separate volatile and semi-volatile compounds within a sample after heating or chemical treatment (Figure 16) and provide a spectral signature of each compound. In order to achieve the separation of a wide range of volatile compounds potentially released from the sample, the GC is composed of four different and complementary analytical channels (Table 7), all including a capillary column dedicated to a specific range of chemical species. As on the Rosetta mission's COSAC experiment, MOMA will carry a chiral GC column with the capability to separate molecular enantiomers of chiral compounds from various chemical families; in some cases, after the compounds are derivatized with the appropriate derivatization reagent. The use of a chiral column enables the extraterrestrial determination and quantification of the enantiomeric excess of chiral molecules. The quantification of enantiomeric excess could reveal information about whether martian organic enantiomers are in a racemic ratio, if they express an enantiomeric bias, or even homochirality, a molecular quality considered to be a signature of terrestrial biology (Chapter III).

I.4. Thesis objectives and organization

This thesis approaches its science and technical questions from the foundational idea that life is composed of, and generates, organic matter. Figure 20 summarizes the chapters of this thesis along with the sample under testing (and its closeness to a martian sample) and the fidelity of the experimental setup to the space experiments of interest. This thesis focuses on the search for organic matter using the Viking Lander GC-MS and the future ExoMars MOMA GC-MS experiments, with some applications also to the MSL SAM experiment. The general science and technical objectives which are targeted and explored in this thesis are the following. §.1. Are there organic molecules on the surface of Mars and what are their nature and their abundance? §.2. What is the origin of the organic molecules detected? §.3. What is the role of the mineral matrix on the analysis? §.4. What are the capabilities and limitations of space instrument components and protocols to detect organic molecules on Mars? §.5. Are there analytical biases and/or constraints related to the flight-like GC-MS analysis, laboratory setups and their fidelity to the flight experiments of interest, and sample analogs? If so, what are some solutions or ways to better simulate the experiment in the laboratory? Chapter II addresses the search for organic compounds on Mars by a reanalysis of the Viking GC-MS data based on new understandings of the martian surface environment since the Viking mission. A directed search for chlorobenzene is described, as well as a discussion of potential chlorine and carbon sources of the chlorobenzene molecule.

Chapter III explores the capabilities of the ExoMars 2022 MOMA chromatographic columns to separate and detect a range of organic and inorganic volatile compounds. This chapter demonstrates the importance of retention time libraries for interpretation of data on Mars. Parameters such as retention time, peak shape, and mass spectrum are compared and provide a calibration for the differences that can be expected between laboratory tests and engineering tests units (ETUs). These laboratory tests utilize flight spare columns from the same batch as those purchased for the flight model, though do not consider certain flight-like hardware components and operational parameters, such as adsorption/thermal desorption trapping and a complex gas processing system, which can be important to the detection of targeted molecules.

Chapter IV explores the capability of the MOMA GC-MS package (pyrolysis-, derivatization-and thermochemolysis-GC-MS) to enable detection of organic compounds in the presence of a montmorillonite mineral matrix.

Chapter V is a perspectives chapter which presents a literature survey of demonstrated detections of amino acids by MTBSTFA derivatization in the context of the fidelity of laboratory experiments to the space experiment. The chapter emphasizes the increasing complexity to interpretation of both flight-like data and data collected on natural samples through exploration of preliminary tests on laboratory setups for MOMA-like thermodesorption and derivatization of natural samples. Perspectives and suggestions are given for future experimentation. Finally, a conclusion section briefly summarizes the main findings, results, and recommendations of this thesis. Introduction

The twin 1976 Viking landers (VL-1 and VL-2) performed the first in situ search for organics on the martian surface. Each lander carried a GC-MS instrument, which was used to search for organics in regolith samples excavated with a robotic arm [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. A total of four samples (two at each landing site) were analyzed, each multiple times, by rapidly heating the sample to one of four temperature steps (50, 200, 350, or 500°C) followed by a 15 s hold, before sweeping the volatilized components into a GC column for separation prior to MS detection. Hydrocarbons and fluorocarbons were detected in all runs and attributed to terrestrial contamination [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. All reported compounds, with the exception of chloromethane detected by VL-1 at levels of 15 parts per billion (ppb); and dichloromethane detected by VL-2 at levels of 2-40 ppb, were identified in in-flight blank runs despite at a lower level. Despite not being identified in the blank runs, the chloromethane and dichloromethane were attributed to either terrestrial contamination resulting from the preflight use of chlorinated cleaning solvents, or from the reaction of absorbed traces of methanol and HCl [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. While [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] did not rule out the possibility that the chloromethane may have been indigenous to the sample, they did not consider the possibility of production of chloromethane in the oven or in the instrument, since they did not know there were oxychlorides in the martian soil.

While today the possibility of chloromethane or chlorobenzene indigenous to the martian soil cannot be excluded, it is unlikely, due to the volatility of these compounds [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] also argued that the detection of chloromethane and dichloromethane in the absence of other related chlorinated compounds suggests a terrestrial origin. A variety of aromatic parts per billion by weight (ppbw) higher than can be explained by background contamination. These chlorinated hydrocarbons were interpreted as thermal decomposition reaction products of martian oxychlorine species and organic carbon derived from martian or exogenous sources such as meteorites, comets, or interplanetary dust particles.

Table 4: Summary of Viking GC-MS data. Note: some analysis conditions for the four martian samples from Table 1 in [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] are included. All VL-1 runs used 2-3 mL of 13 C-labeled carbon dioxide to sweep away any emerging volatile material from the oven to the gas chromatographic column. Early VL-2 runs utilized H2 gas instead of 13 CO2 in order to regulate the effluent divider status and to maximize the amount of sample transferred from the oven to the GC column [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. In addition, the H2 mode replaced the gas in all void areas by hydrogen, allowing a more reliable detection of CO2. For each GC run, the temperature of the GC column is held at 50˚C for 12 min, followed by a linear increase up to 200˚C over a period of 18 min, and then held at this temperature for either 18, 36, or 54 min for a total run time of 48, 66, or 84 min [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. The SAM detection of organic carbon indigenous to a martian sample and the seemingly widespread distribution of perchlorate on the planet [START_REF] Glavin | Evidence for perchlorates and the origin of chlorinated hydrocarbons detected by SAM at the Rocknest aeolian deposit in Gale Crater[END_REF][START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF][START_REF] Ojha | Spectral evidence for hydrated salts in recurring slope lineae on Mars[END_REF] prompted this reconsideration of the original Viking GC-MS data sets and search for evidence of chlorinated hydrocarbons that could be reaction products of perchlorate and organic carbon indigenous to the martian sample in the Viking GC-MS ovens. Chlorobenzene is the most abundant chlorinated hydrocarbon detected by SAM with a known organic carbon source indigenous to the martian sample [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. It is also interesting to look for an aromatic chlorohydrocarbon based on the expectation that such compounds should occur in suites [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF][START_REF] Steininger | Influence of magnesium perchlorate on the pyrolysis of organic compounds in Mars analogue soils[END_REF]. The Viking GC-MS data sets were searched for evidence of chlorobenzene. Chlorobenzene signals were quantified and compared to the abundances of chloromethane and dichloromethane reported by the Viking GC-MS team. The presence of chlorobenzene was considered in the light of possible sources of organic carbon that could have reacted with perchlorate during pyrolysis, such as organic carbon indigenous to the martian sample and instrument contamination. The Viking background was searched for compounds that might have been released by the degradation of the columns by HCl, as have been detected in SAM.

Sample

II.2 Materials and methods

II.2.1 Viking GC-MS data

The derived data products from the Viking GC-MS instrument were mass scans from the mass spectrometer, which had a dynamic range of 6-7 orders of magnitude [START_REF] Biemann | Search for Organic and Volatile Inorganic Compounds in Two Surface Samples from the Chryse Planitia Region of Mars[END_REF]). It appears from the existing data sets that the mass range (m/z) was 12-215. A complete mass spectrum was scanned every 10.24 s [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. Up to 500 scans were produced for each GC-MS run [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]) corresponding to about 48, 66, and 84 min of GC elution time in the case of three different gas chromatographic column temperature protocols. The total data were 16 GC-MS runs (one cruise blank for each lander, five at VL-1, and nine at VL-2) focused on the analysis of four soil samples (Table 4).

The 16 Viking GC-MS runs are preserved on 16-mm microfilms at the NASA Space Science Data Coordinated Archive and were individually scanned to digital image files for this analysis.

Although the Viking team originally published mass spectra and gas chromatographs (signal intensity versus time), only the mass spectra (ion intensity versus m/z) are available. Chromatographs for specific ions were reconstructed (Figure 22, bottom right) using the digital mass spectra scans by plotting the ion intensity versus GC run time. The ion intensity shown on these digital mass spectra scans, and used in this chapter, is given in arbitrary units in values from zero to 9.99 × 10 6 . The order of magnitude of these units is consistent with realistic values for the total ion current, but there is no direct information available on whether this is a relative or absolute value.

II.2.2 Presence and abundance of chlorobenzene in Viking GC-MS data

The SAM team identified chlorobenzene by its characteristic peak at m/z 112 with a corresponding peak at m/z 114 at about one third the intensity. The Viking data was screened for coincident peaks at m/z 112 and m/z 114 close to the background noise. The known abundance of toluene (0.04-0.08 parts per billion by mass or ppbm) in VL-2, Sample 2, GC-MS Run 10039 [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] was used as a reference compound to estimate the abundance of the probable chlorobenzene signal.

The only toluene fragment detected by VL-2 (m/z 91) was used to calculate all other toluene mass fragments based on the National Institute of Standards and Technology (NIST) standard. Similarly, the NIST standard was used to calculate the mass fragments of chlorobenzene based on the mass fragments measured by VL-2 (m/z 112 and m/z 114). In these calculations, all m/z were considered which have ≥10% of the intensity of the major m/z peak according to the NIST standard (i.e., m/z 91, m/z 92, m/z 65, and m/z 39 for toluene and m/z 112, m/z 114, m/z 77, and m/z 51 for chlorobenzene). The sum of the intensities of each mass fragment was calculated for toluene and chlorobenzene, and the toluene-to-chlorobenzene intensity ratio was used to derive a lower limit of chlorobenzene abundance based on the toluene abundance (0.04-0.08 ppbm) reported by [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. The final result was corrected by a factor 1.2, corresponding to the ratio of the ionization cross section of chlorobenzene/toluene [START_REF] Bart | Electron impact ionization: Measurements of absolute cross-sections and crossbeam studies[END_REF][START_REF] Harrison | Total cross sections for ionization by electron impact[END_REF].

II.3 Results

II.3.1 Chlorobenzene in Viking GC-MS data

The first probable detection of chlorobenzene in the Viking GC-MS data sets was identified in VL-2, Sample 2, Run 10039 (Figure 22,top). In Scan 148 (out of 411 scans) of this run there was a clear peak at m/z 112 with a coincident peak at about one third the intensity at m/z 114. There was also a visible peak at m/z 112 in Scans 147 and 149, and a peak at m/z 114 also in Scan 149.

Outside of Scans 147-149 there was no signal at m/z 112 or 114 in the rest of the run. No signals were found at m/z 112 or m/z 114 in the blank run for VL-2. For the mass scan where m/z 112 and m/z 114 were both seen most clearly (VL-2, Run 10039, Scan 148), the magnitude of the m/z 112 peak in arbitrary units was 685 compared to a base peak (m/z 81) value of 7,692 (in a scan where all peaks were normalized to the most abundant ion > m/z 46).

Next, all Viking GC-MS runs were searched in the range surrounding Scans 147 to 149, corresponding to an approximated chlorobenzene GC retention time. No peaks at m/z 112 or m/z 114 were found in VL-1. However, there were m/z 112 and/or m/z 114 peaks found in VL-2 data recurring at the same scan number range (Scan 147-150; Figure 23). Additionally, every scan in every run was searched for any signal at m/z 112 or m/z 114, in case the signal occurred at a different scan number range due to a difference in temperature or other physical condition between VL-1 and VL-2, but no other peaks were found. The chlorobenzene signals were found in two samples at the VL-2 site (Bonneville and under a rock named Badger), only at temperatures between 350 and 500°C, similar to dichloromethane (Table 5). In both instances, the measured chlorobenzene signal was highest at 500°C.

Constraining the coincident signal of m/z 77, another important fragment for chlorobenzene, is more nuanced. There is a background signal at m/z 77 throughout most of this run as well as the blank run. This background is accounted for by subtracting the averaged m/z 77 signal from two scans before (Scans 145-146) and two scans after (Scans 150-151) the three scans where m/z 112 and/or m/z 114 are identified. The result is the mass peaks for m/z 77, m/z 112, and m/z 114 shown in Figure 22 (bottom left), which resemble the relative signal for chlorobenzene identified by SAM in [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF].

Estimated chlorobenzene abundances were 1 to 2 orders of magnitude lower than dichloromethane abundances reported by [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]Table 5). The lower limit of chlorobenzene abundance in the Bonneville sample ranged between 0.1 ppbm and 0.5 ppbm. The lower limit of chlorobenzene abundance under Badger Rock ranged between 0.08 ppbm and 0.7 ppbm. [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] used the chloromethane abundance ratio of m/z 50 to m/z 52 detected by Viking to interpret a 35 Cl/ 37 Cl isotope ratio of about 3:1. This is within the bounds of the ~3:1 to ~5:1 ratio of m/z 112 to m/z 114 for the chlorobenzene peak found in SAM EGA and GC-MS Cumberland samples [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. The same calculation is done for the chlorobenzene signal in Viking and find a 35 Cl/ 37 Cl isotope ratio of ~2.5:1. This is a rough estimate because the ratio is calculated based on only Scan 148 of Run 10039, where the clearest signal is observed from both m/z 112 and m/z 114. If an average isotope ratio is taken using Scans 148 and 149 of Run 10039, where the m/z 112 and m/z 114 peaks are both visible, the ratio is ~5:1. It is next important to identify the origin of the chlorobenzene in Viking, in order to determine if the signal is evidence of organic carbon indigenous to the martian sample present in the Viking ovens. Because of the high vapor pressure of chlorobenzene, it is unlikely that it was present as such in the martian regolith, although this hypothesis cannot be ruled out with the available data.

The detected chlorobenzene is more likely a combination of chlorine-and carbon-bearing compounds in the Viking ovens, as is the case for some SAM samples, and it is assumed that the contribution of chlorine in the Viking GC-MS comes from GC pyrolysis rather than being produced by irradiated perchlorate [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Glavin | Evidence for perchlorates and the origin of chlorinated hydrocarbons detected by SAM at the Rocknest aeolian deposit in Gale Crater[END_REF]). The following sections address the origin of both the chlorine and the carbon as possible terrestrial contaminants or as indigenous to the martian parent sample.

II.4.2 Chlorine source

A possible source of chlorine could be chlorinated solvents used to clean the instrument before flight (e.g., dichloromethane) per [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. However, the boiling points of dichloromethane (~40°C at 1 atm) is very low compared to the temperature at which chlorobenzene was first detected (350°C), and the temperature at which the chlorobenzene signal was highest (500°C), both of which overlap the temperature range where decomposition of oxychlorine compounds occurs [START_REF] Archer | Abundances and implications of volatile-bearing species from evolved gas analysis of the Rocknest aeolian deposit, Gale Crater, Mars[END_REF]. Since the increase in abundance of chlorobenzene correlates to the temperature range at which oxychlorine compounds decompose, it is concluded that the chlorine source is martian, probably the result of the decomposition of martian perchlorate or chlorate salts in the Viking ovens and represents indirect evidence of the presence of oxychlorine species in samples analyzed by VL-2. Additionally, the release of HCl during pyrolysis can be derived from the reaction of SO2 with chloride salts and sulfates in the presence of water. However, sulfates only begin degrading around 600°C, above the temperature range of the Viking ovens [START_REF] Sutter | Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune[END_REF].

II.4.3 Carbon source

The carbon source responsible for the chlorobenzene signal is more difficult to assert (Figure 21).

Here two possibilities are considered: (1) instrument background due to terrestrial organic contaminants; and (2) organic carbon indigenous to the martian sample. Organic carbon is considered as the source for the chlorobenzene discussed in this chapter, since carbon-bearing phases such as carbonates, while quite common, do not degrade within the Viking GC-MS temperature range of 50-500°C (Boynton et al., 2009;[START_REF] Sutter | Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune[END_REF].

II.4.3.1

Instrument background as the organic carbon source of chlorobenzene [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF] reported contaminants eluting at specific scan numbers in VL-2 GC-MS runs (Table 5). An additional background is revealed as a series of mass peaks in all scans (i.e., throughout the chromatograph), and which is also seen in the cruise blank runs, suggesting that these mass peaks are due to contamination in the instrument. A source of contaminants recognized by the Viking team were organic solvents used to clean the walls of the GC-MS ovens. Among these, acetone had the highest concentration of the listed contaminants used [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]; however, this possibility can be ruled out as the pyrolysis of acetone with HCl does not lead to the formation of chlorobenzene (Navarro-González, private communication, 2018).

Another source of instrument contamination are materials derived from the instrument itself, either through bleeding of the GC column or from sticky organic compounds in the walls of the MS system, which have also been observed in the SAM GC-MS system [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. For example, the detection by the SAM GC-MS of some aromatic hydrocarbon fragments, including low levels of chlorobenzene in blanks, has been attributed to the degradation of Tenax-TA [poly (2,6-diphenyl-p-phenylene oxide] used in hydrocarbon and injection traps upstream from the GC columns. Tenax-TA degradation was likely caused by HCl released from the decomposition of martian perchlorate in the GC columns [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF].

In the case of the Viking GC-MS, a liquid-modified organic adsorbent consisting of 60-to 80mesh Tenax-GC was used as packing material in the GC column [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF]. Tenax-GC and Tenax-TA are essentially the same material, though Tenax-GC is known to be less stable under heating. Like in the case of the SAM instrument, degradation of the Tenax-GC material by HCl released from the decomposition of martian perchlorate could explain several mass fragments seen as background in the Viking GC-MS data, including biphenyl (m/z 154), which reoccurs in VL-1 scans but is never seen in VL-2; styrene (m/z 104); xylene and ethylbenzene (m/z 106); cyclopentene and cyclopentadiene (m/z 66 and 67); or trichloromethane (m/z 83 and 85). In addition, the mass spectra were searched for phenol (m/z 94), a precursor of chlorobenzene at high temperature in the presence of an oxychlorine phase. Small peaks at m/z 94 were found eluting early in VL-2, Sample 2, Run 10039 in the phase where the column is initially held at 50°C, but there were no m/z 94 peaks in scans where a chlorobenzene signal was observed. Mass peak m/z 94 began to appear consistently after Scan 200 in both the VL-2 blank run and VL-2, Sample 2, Run 10039. Unfortunately, phenol is very refractory and may not elute as such from the GC column. Therefore, it cannot be ruled out with the available data that the carbon-bearing compound which contributed to the chlorobenzene signal found in the VL-2 GC-MS data set was due to Tenax-GC degradation.

The chromatograph for m/z 81 (attributed to difluorodimethylsilane, as in SAM) was reconstructed using the digitized mass spectra scans for VL-2, Sample 2, Run 10039 (Figure 22, bottom right).

There is a recurring signal throughout most of VL-2 with recurring peaks at m/z 81 (base peak).

While the m/z 81 background signal in Run 10039 decreases over the run time, which is consistent with column bleeding, there is no indication that the behavior of this background signal correlates to the occurrence of the chlorobenzene; that is, there is no change in the behavior of the background at the same time as the chlorobenzene, which would indicate that its organic carbon source is due to instrument contamination. To truly assert the origin of the chlorobenzene signal it would be necessary to compare the retention time of chlorobenzene to that of other hydrocarbons known to result from Tenax-GC degradation, using a laboratory reconstruction of the Viking GC column.

II.4.3.2 Organic carbon native to the martian sample as the source of chlorobenzene

An alternative source of carbon to explain the chlorobenzene signal is ppm levels of martian organic carbon in the soil. In this scenario, organic compounds would be released from the mineral matrix in a sample at certain temperatures and react with perchlorate, or its degradation products, forming chlorobenzene prior to detection by the MS. [START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF] showed that chloromethane and dichloromethane were produced this way, but they were not focused on looking for chlorobenzene. However, chlorobenzene is known to be produced in this way as well [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. Indeed, the chlorobenzene signal in VL-2 runs was observed between 350°C and 500°C, consistent with observations by the SAM instrument of chlorobenzene between 250°C and 450°C. In addition, the abundance of chlorobenzene increased with temperature and was highest after two successive 500°C runs in a sample collected from under Badger Rock, in an area where organics would be better protected from ultraviolet radiation (Moores & Schuerger 2012). A higher abundance of chlorobenzene at the highest temperature runs and, in a sample, protected from radiation is compatible with the release of organic compounds trapped in minerals, and it is contrary to the style of release of known contaminants in the instrument, which were detected in highest abundance at lower temperature runs (Figure 24). Therefore, the chlorobenzene signal in VL-2 runs is consistent with an organic carbon source native to the martian sample and reacting with martian oxychlorine species during GC-MS analysis.

II.4.4 Comparison between Viking and SAM

The chlorobenzene abundance in VL-2 is equivalent to ~0.08-1.0 ppbw, while SAM detected 150-300 ppbw of chlorobenzene (above background) in the Cumberland drill sample [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. It is difficult to make a direct comparison between these abundances, due to differences between the instruments and samples. Each GC-MS heats at different temperatures and rates, causing differences in combustion, line loss, and line temperature. The Viking ovens are flash heated, while the SAM ovens are heated at 35°C/min so the chemistry of the reaction inside the oven can be different in these two cases. SAM's Cumberland sample was drilled in a clay-rich region, while VL-2 scooped one of its samples underneath a rock. Additionally, SAM deals with two sources of contamination: a leaked derivatization agent, MTBSTFA, and background from its hydrocarbon trap. In SAM, the leaked MTBSTFA produces a background of chloromethane and dichloromethane, which is impossible to separate from that which may be produced due to ppm levels of organic carbon in the martian sample. The Tenax-TA used in the SAM hydrocarbon trap is responsible for the instrument background of ~12 ppbw of chlorobenzene. While not quantifiably comparable, the Tenax-GC component in Viking could be a source of organic carbon contamination as well.

Figure 24: Trends of relative abundance of compounds identified in VL-2 runs, Sample 1 (Bonneville) and Sample 2 (under Badger Rock). The natural log of the abundance of acetone and dichloromethane (DCM) in ppbw is plotted in order to visualize less abundant compounds clearly. The actual calculated abundance in ppbw is shown for all other compounds (benzene, toluene, xylene, and chlorobenzene or CBZ). The average abundance is used for all compounds.

After an initial heating to 500°C, each sample was heated again at 500°C. The blank run shown on each graph above is the same data, as only one blank run was performed in flight for each of the landers and it was run at 500°C.

II.5 Conclusions

This chapter presents a new identification of chlorobenzene in several VL-2 GC-MS runs. This signal is interpreted as the reaction product of chlorinated compounds with organic carbon compounds at high temperature. The source of the chlorine and carbon of the chlorobenzene are detailed in the following summary of this chapter's results.

The following main conclusions and results which correspond to sections of this chapter are given below.

II.a.

CBZ in several VL-2 GC-MS runs (Sections II.3.1, II.4.1) i. CBZ was identified in several VL-2 GC-MS runs by its mass spectrum. ii. The identified chlorobenzene has a characteristic isotopic ratio between m/z 112 and m/z 114. iii. CBZ was quantified at levels corresponding to 0.08-1.0 ppb (relative to sample mass). iv. CBZ is seen at oven temperatures >200°C with a maximum signal at 500°C. v. VL-1 runs were also searched and no chlorobenzene was identified.

II.b.

Source of chlorine of the CBZ (Section II.4.2) i. The high temperature of the CBZ release (II.a.ii) is not consistent with a terrestrial source of chlorinated compounds such as dichloromethane. ii. The temperature range of CBZ release (II.a.ii.) overlaps with the temperature range where decomposition of oxychlorine compounds occurs.

iii. Due to II.a.iii. and II.b.i. through ii., the chlorine source is determined to be martian. iv. II.b.iii. would suggest perchlorate or other oxychlorines present at the VL-2 landing site.

II.c.

Source of carbon of the CBZ (Section II.4.3) i. An instrument organic carbon souce could be provided by degradation of the Tenax-GC used to pack the Viking GC columns by HCl released from perchlorate decomposition. ii. The highest signal of CBZ was observed in a test of a sample protected from UV radiation (under a rock). iii. II.a.ii. and II.c.ii. are consistent with a martian carbon source reacting with martian oxychlorine species to form CBZ. iv. An instrument organic carbon source has not been ruled out.

The following future studies and recommendations are proposed.

II.R.a.

To corroborate II.a.i. by retention time, a CBZ chemical standard should be tested on a laboratory reconstruction of the Viking GC column with the same packing material.

II.R.b.

To test II.c.i. and to follow up on II.c.iv., it would be necessary to compare the retention time of CBZ and other hydrocarbons known to result from Tenax-GC degradation using a laboratory reconstruction of the Viking GC column with the same packing material.

Chapter III: Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars

Based on a paper published in Planetary Space Sciences [START_REF] Guzman | Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars[END_REF] Abstract Mars is our planetary neighbor and is now known to host trace levels of organic matter at its surface. However, little is known of the organic molecular composition or the survival potential for organic biosignatures, such as the enantiomeric excess of amino acids or the carbon chain patterns of lipid hydrocarbons, as a function of depth below the martian surface. The Mars Organic Molecule Analyser (MOMA) is an instrument onboard the Rosalind Franklin rover that is scheduled to be launched to Mars in the summer of 2022 as part of the ExoMars mission. This experiment includes a gas chromatograph instrument dedicated to the in situ analysis of organic molecules and their enantiomers present in martian samples collected by the rover at the surface down to 2 m depth. In order to evaluate the performance of the integrated chromatographic system which was selected for the flight model, experiments were carried out with a laboratory setup that reproduced the flight configuration and mimicked the in situ operating conditions. This study shows that the column instrument package can separate and detect a wide range of organic and inorganic volatile compounds, from noble gases to hydrocarbon chains with up to 29 carbon atoms (C29). The enantiomeric resolution of selected chiral chemical standards is studied and laboratory results are compared to: i. tests performed with the same instrumental setup but using a natural sample spiked with amino acids in order to evaluate the influence of a mineral phase on the analysis, and ii. tests run on a MOMA engineering test unit (ETU) which is representative of the flight model. Tests on the more complex sample and the more flight-like instrument allows a comparison with laboratory results, in order to confirm that laboratory data are reliable for supporting peak identification within flight data. The obtained results demonstrate the ability of the gas chromatographic subsystem to identify a wide range of organic and inorganic volatile compounds, including biomolecular signatures, within the constrained space operating conditions of MOMA. The results form a retention time and mass spectral database for MOMA which will be critical for analysis of the eventual flight data.

III.1 Introduction

As introduced in Chapter I (Section I.3), gas chromatography coupled to mass spectrometry (GC-MS) was first used for in situ Mars exploration by the twin Viking landers, which arrived on Mars in 1976 with the aim of searching for signs of life in the near surface environment. In support of the three Viking biology experiments, the Viking landers conducted an organic inventory of the martian regolith, since primitive life on Earth is understood to have originated from the processing of organic molecules by liquid water [START_REF] Brack | Origin of Life[END_REF]. The Viking landers and the results of the Viking GC-MS instruments are the topic of Chapter II. The Viking GC-MS experiment did not detect organic molecules, with the exception of chloromethane (detected by Viking Lander 1 at levels of 15 parts per billion by mass) and dichloromethane (detected by Viking Lander 2 at levels of 2-40 parts per billion by mass). These signals were at first attributed to cleaning agents used on the spacecraft before launch [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF], but is now an open question posed in the literature [START_REF] Guzman | Identification of Chlorobenzene in the Viking Gas Chromatograph-Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars[END_REF][START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF] and by Chapter II of this thesis. The Viking results represent a paradigm shift within Mars astrobiology exploration. The possibility of widespread microbial life at the martian surface was replaced with an understanding that, given such low detection limits for organic compounds determined at the time of the Viking results, it is difficult to maintain that living organisms based on the terrestrial carbon-hydrogen-nitrogenoxygen chemistry are widely distributed at the surface of Mars [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF][START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF].

Additionally, the Viking GC-MS results required a mechanism for the destruction of organic molecules at Mars. Mechanisms for the destruction of organic molecules at Mars are discussed in Section I.2.3.2. It was understood at the time of Viking and has now been estimated that significant amounts of carbon material are delivered to the martian surface each year from at least the interplanetary medium [START_REF] Flynn | The delivery of organic matter from asteroids and comets to the early surface of Mars[END_REF]) (Section I.2.3.1). Since the Viking result, radiation has been studied as a degradation and alteration mechanism for organic matter in the context of Mars, e.g., the influence of the ultraviolet radiation environment on organic matter at the martian surface [START_REF] Stalport | The Photochemistry on Space Station (PSS) Experiment: Organic Matter under Mars-like Surface UV Radiation Conditions in Low Earth Orbit[END_REF]. The Viking result also suggested a powerful oxidant capable of converting all organic molecules in the martian regolith to carbon dioxide rapidly relative to the rate at which they arrive from exogenous sources [START_REF] Benner | The missing organic molecules on Mars[END_REF]. There are now multiple oxidants assumed to be present at the martian surface or which have been detected already on Mars [START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF]. The 2008 Phoenix mission confirmed the presence of oxychlorine phases in the form of perchlorate at the northern pole of Mars [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF]). Perchlorate has also been suggested at Gale Crater by the GC-MS analysis of Curiosity rover's SAM instrument suite [START_REF] Leshin | Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover[END_REF][START_REF] Sutter | Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune[END_REF]. The unexpected discovery of perchlorate by Phoenix resulted in another paradigm shift in which the community began to question if pyrolysis-GC-MS could enable the detection of trace levels of organics [START_REF] Navarro-González | Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars[END_REF]). Curiosity's SAM instrument, in addition to significantly advancing our understanding of martian habitability, has shown that a GC-MS instrument can detect organics in martian samples collected within the 5 cm drill capability of the Curiosity rover despite the challenges of perchlorate (Eigenbrode et al. 2018;[START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Szopa | First Detections of Dichlorobenzene Isomers and Trichloromethylpropane from Organic Matter Indigenous to Mars Mudstone in Gale Crater, Mars: Results from the Sample Analysis at Mars Instrument Onboard the Curiosity Rover[END_REF].

As introduced in Section I.3.2, the MOMA experiment is scheduled to travel to Mars onboard the Rosalind Franklin rover of the joint ESA/Roscosmos ExoMars 2022 mission [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF].

MOMA is a miniaturized chemical laboratory specifically dedicated to analyzing the organic and inorganic content of samples collected by the rover at the martian surface and subsurface [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. Through these measurements, MOMA will contribute to characterizing the past and present habitability of Oxia Planum, the landing site selected for the rover, where features and minerals associated with flowing liquid water were observed from the Mars orbit [START_REF] Quantin | Oxia Planum, The Landing Site for ExoMars[END_REF]. First of all, MOMA will have the capability to detect non-statistical distributions of molecules, or molecular patterns of astrobiological interest, with the Laser Desorption/Ionization Mass Spectrometry (LDMS) mode. Laboratory experiments have shown the LDMS mode to be less sensitive to the presence of oxidizing reagents such as perchlorate [START_REF] Li | Detection of Trace Organics in Mars Analog Samples Containing Perchlorate by Laser Desorption/Ionization Mass Spectrometry[END_REF]. MOMA will also have the capability to analyze drilled samples from up to 2 meters in depth. These samples may be protected from the oxidation processes discussed earlier and from solar and galactic radiation over geologic timescales [START_REF] Pavlov | Degradation of the organic molecules in the shallow subsurface of Mars due to irradiation by cosmic rays[END_REF]. Therefore, samples may contain more abundant and pristine organic materials.

MOMA includes a gas chromatographic (GC) package, developed with experience from the SAM instrument acquired by the laboratory group supervising this thesis, and an ion trap mass spectrometer (ITMS) [START_REF] Brinckerhoff | Mars Organic Molecule Analyzer (MOMA) mass spectrometer for ExoMars 2018 and beyond[END_REF]. The GC-MS will separate volatile and semivolatile compounds within a sample after heating or chemical treatment and provide a spectral signature of each compound. This combination allows the strict identification of organic molecules. In order to achieve the separation of a wide range of volatile compounds potentially released from the sample, the GC is composed of four different and complementary analytical channels (Table 7), all including a capillary column dedicated to a specific range of chemical species. As on the Rosetta mission's Cometary Sampling and Composition (COSAC) experiment, MOMA will carry a chiral gas chromatographic column with the capability to separate molecular enantiomers of chiral compounds from various chemical families; in some cases, after the compounds are derivatized with the appropriate derivatization reagent [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF][START_REF] Meierhenrich | Evaluating the robustness of the enantioselective stationary phases on the Rosetta mission against space vacuum vaporization[END_REF][START_REF] Myrgorodska | Enantioselective Gas Chromatography in Search of the Origin of Biomolecular Asymmetry in Outer Space[END_REF]. The use of a chiral column enables the extraterrestrial determination and quantification of the enantiomeric excess of chiral molecules.

The quantification of enantiomeric excess could reveal information about whether martian organic enantiomers are in a racemic ratio, if they express an enantiomeric bias, or even homochirality, a molecular quality considered to be a signature of terrestrial biology (Section I.1.2.2).

Additionally, some of the compounds of astrobiological interest for MOMA, and specifically those biomolecules displaying the property of homochirality in terrestrial life (e.g., amino acids), contain labile hydrogen atoms in polar functional group (e.g., -OH, -COOH, -NH, -SH, or -PH). These kinds of compounds tend to self-react or to be strongly adsorbed by the GC column stationary phase, which prevent their analysis by GC-MS. To overcome this analytical problem, a derivatization reagent can be utilized to produce controlled reactions which protect the reaction group against unwanted reactions and thermal destabilization [START_REF] Knapp | Handbook of Analytical Derivatization Reactions[END_REF]. As introduced in Chapter I (Section I.3.2.3), MOMA carries three different chemical reagents, MTBSTFA and DMF-DMA for derivatization and TMAH for thermochemolysis, each one with the capability to reveal specific properties of organic molecules. DMF-DMA is the only reagent selected which enables the detection of molecular enantiomers and has so far never been utilized in the analysis of martian samples. The MOMA gas chromatographic package is heavily aided by these wet chemistry capabilities in order to meet its objectives, both to enable the detection of molecules with labile polar functional groups and, in the case of DMF-DMA, to enable the detection of molecular enantiomers.

The flight model (FM) of MOMA is now finalized and integrated in the rover, and the range of operating conditions of the instrument under the Mars surface environmental conditions has been constrained (e.g., carrier gas flow rates, transfer line temperatures). Expected GC-MS operating conditions for Mars are shown in Table 8. This chapter will present the final chromatographic column package selected for MOMA, the analytical procedures that will be used on Mars, a retention time and mass spectral library to support the analyses of eventual Mars flight data, and a demonstration of the analytical performance of a laboratory system that simulates the flight experiment and the in situ operating conditions. Special attention is given to the enantiomeric separation capabilities which have not been performed on Mars before. A set of chemical compounds of interest for Mars near-surface science and astrobiology was selected and analyzed across each of the four columns. The column instrument package can separate and detect a wide range of organic and inorganic volatile compounds, from noble gases to hydrocarbon chains with up to 29 carbon atoms (C29). Next, a study of selected chiral chemical standards demonstrates the analytical performance of the chiral column based on enantiomeric resolution of these molecules.

The results of the laboratory chiral studies were compared to tests performed with the same laboratory setup but using a natural sample, which included a mineral phase, spiked with amino acids, in order to test a more realistic case. The laboratory studies were also compared to tests run on a MOMA engineering test unit (ETU) to show the relevance and utility of column testing performed in the laboratory for interpretation and data treatment of MOMA flight data. Because any planetary instrument with the capability to enable biosignature detection is unlikely to demonstrate a single indisputable positive result, it is critical to produce a group of complimentary observations to be assessed together for interpretation. The chromatographic column package has the capability to detect multiple parameters indicative of terrestrial biology.

III.2 Materials and methods

III.2.1. Laboratory samples

III.2.1.1. Selection of standards

Among the chemical families of organic molecules that can be deposited on Mars via exogenous sources and/or synthesized on Mars endogenously, the number of organic species that could be tested experimentally is too large to lead a systematic study in a reasonable amount of time. Therefore, the following specific chemical families, and specific molecules within those families, have been selected for our study of the MOMA GC columns and are summarized in Table 6. The compounds are appropriate for the design requirements outlined for the main classes of chemical species to be separated by the MOMA GC columns [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF].

The organic compounds selected for this study were targeted according to several criteria:

• Potential to elute across a range of retention times from the GC columns, e.g. linear and ramified alkanes with a molecular mass range from 100.21 g•mol -1 (heptane) to 563.08 g•mol -1 (tetracontane). • Representatives of several key families of molecules, thus several physio-chemical characteristics, e.g. alkanes without a labile polar functional group versus alcohols with an -OH chemical function. • Potential presence in the samples that can be collected at Mars's surface and sub-surface, i.e. the molecules selected are among the most abundant within known exogenous sources or correspond to evolution products of organic molecules under Martian environmental conditions, e.g. carboxylic acids as products of oxidation [START_REF] Benner | The missing organic molecules on Mars[END_REF] and potential precursors to previously detected chlorinated hydrocarbons (Miller et al. 2016b). • Organic molecules of interest for astrobiology, e.g. chiral amino acids.

Amino and carboxylic acids are particularly interesting for testing on the MOMA gas chromatographic package, since they are of particular interest for astrobiology [START_REF] Davila | Chance and necessity in biochemistry: implications for the search for extraterrestrial biomarkers in Earth-like environments[END_REF], require derivatization for optimal detection by GC-MS [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF], and have been detected in meteorites and comets [START_REF] Altwegg | Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov-Gerasimenko[END_REF][START_REF] Glavin | Amino acids in the Martian meteorite Nakhla[END_REF][START_REF] Glavin | Re-examination of amino acids in Antarctic micrometeorites[END_REF][START_REF] Sephton | Pyrolysis and mass spectrometry studies of meteoritic organic matter[END_REF]). Among our selected amino acids, only glycine does not possess the property of chirality. Glycine (C2H5NO2) and alanine (C3H7NO2) have both been detected in micrometeorites and carbonaceous chondrites [START_REF] Ehrenfreund | Extraterrestrial amino acids in Orgueil and Ivuna: tracing the parent body of CI type carbonaceous chondrites[END_REF][START_REF] Maurette | Carbonaceous Micrometeorites and the Origin of Life[END_REF][START_REF] Pizzarello | The Nature and Distribution of the Organic Material in Carbonaceous Chondrites and Interplanetary Dust Particles[END_REF][START_REF] Sephton | Organic matter in carbonaceous meteorites: past, present and future research[END_REF]Sephton & Botta 2008), and, in the case of glycine, in comet material [START_REF] Altwegg | Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov-Gerasimenko[END_REF][START_REF] Elsila | Cometary glycine detected in samples returned by Stardust[END_REF]. In addition to the potential for amino acids to be brought to the surface of Mars by exogenous sources, they can be synthesized by various endogenous and abiotic processes, such as via hydrothermal vents [START_REF] Hennet | Abiotic synthesis of amino acids under hydrothermal conditions and the origin of life: A perpetual phenomenon[END_REF][START_REF] Marshall | Hydrothermal synthesis of amino acids[END_REF], atmospheric processes [START_REF] Cleaves | A Reassessment of Prebiotic Organic Synthesis in Neutral Planetary Atmospheres[END_REF], and under the influence of irradiation [START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF]) (Chapter I, Section I.2.3.1).

The selected amino acids include those heavily studied (glycine) and largely undiscussed (glutamic acid) in relation to martian environmental conditions. The potential evolution of glycine under martian environmental conditions has been a topic of numerous experimental studies [START_REF] Oró | The photolytic degradation and oxidation of organic compounds under simulated Martian conditions[END_REF][START_REF] Poch | Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions[END_REF][START_REF] Stoker | Organic degradation under simulated Martian conditions[END_REF][START_REF] Ten Kate | The effects of Martian near surface conditions on the photochemistry of amino acids[END_REF]. While laboratory studies show that alanine is unstable in the martian oxidation surface environment [START_REF] Benner | The missing organic molecules on Mars[END_REF] and under martian surface UV radiation (ten Kate et al. 2006), studies have shown it would be preserved in minerals such as magnesium sulfates [START_REF] François | Magnesium sulfate as a key mineral for the detection of organic molecules on Mars using pyrolysis[END_REF]) and clays [START_REF] Bowden | Intracrystalline lipids within sulfates from the Haughton Impact Structure-Implications for survival of lipids on Mars[END_REF][START_REF] Kennedy | Mineral Surface Control of Organic Carbon in Black Shale[END_REF] and its potential subsurface stability may be elucidated by MOMA.

Of the carboxylic acids that were tested, oxalic acid is the most abundant dicarboxylic acid in several carbonaceous chondrites [START_REF] Peltzer | The chemical conditions on the parent body of the murchison meteorite: Some conclusions based on amino, hydroxy and dicarboxylic acids[END_REF][START_REF] Pizzarello | Sutter's Mill dicarboxylic acids as possible tracers of parent-body alteration processes[END_REF][START_REF] Shimoyama | Dicarboxylic Acids in the Murchison and Yamato-791198 Carbonaceous Chondrites[END_REF]. Benzoic and mellitic acids have both been proposed as metastable and stable intermediate oxidation state molecules formed from polycyclic aromatic hydrocarbons (PAHs) potentially provided by exogenous sources [START_REF] Benner | The missing organic molecules on Mars[END_REF]. Mellitic acid has been studied under martian irradiation conditions [START_REF] Poch | Laboratory insights into the chemical and kinetic evolution of several organic molecules under simulated Mars surface UV radiation conditions[END_REF][START_REF] Stalport | Investigating the Photostability of Carboxylic Acids Exposed to Mars Surface Ultraviolet Radiation Conditions[END_REF]) and would be destroyed by nearly 63% after a few hours of irradiation in addition to undergoing dehydration leading to the formation of mellitic acid trianhydride [START_REF] Archer | The Martian Near Surface Environment: Analysis of Antarctic Soils and Laboratory Experiments on Putative Martian Organics[END_REF][START_REF] Stalport | The Photochemistry on Space Station (PSS) Experiment: Organic Matter under Mars-like Surface UV Radiation Conditions in Low Earth Orbit[END_REF]). In addition to aromatic and di-carboxylic acids, several long chain carboxylic acids were tested which, although terrestrial contamination cannot be ruled out, have been detected in carbonaceous chondrites with between 13 and 23 carbon atoms (Murchison) and with between 2 and 12 carbon atoms (Asuka-881458) [START_REF] Deamer | Amphiphilic components of the murchison carbonaceous chondrite: Surface properties and membrane formation[END_REF][START_REF] Naraoka | Molecular Distribution of Monocarboxylic Acids in Asuka Carbonaceous Chondrites from Antarctica[END_REF].

III.2.1.2. Non-derivatized standards

For the laboratory experiments, the non-derivatized linear alcohols were diluted in methanol at 10 - 4 vol. % in order to inject precise amounts of chemical standards and without risking saturation of the stationary phases or detector. For the same reason, the C7 to C40 linear alkanes were diluted in hexane at a 1 g•L -1 mass concentration. The 3-methylhexane and 3-methylheptane were diluted in cyclohexane at 10 -3 vol%. Liquid and solid compounds were supplied by Sigma-Aldrich, whereas gaseous components were supplied by Air Liquide, Linde and Messer. 0.5 µL of the liquid solutions were injected into the GC-MS using a 1 µL liquid syringe (SGE) and 1 mL of the gas mixtures were injected using a 5 mL gas syringe (SGE). Figure 32 shows a run with no syringe injection performed directly after a run with a 1 mL syringe injection of the noble gas mixture due to saturation of the column with this high injection volume.

III.2.1.3. Derivatized standards

Solid amino acids and carboxylic acids were diluted in demineralized water at a concentration of 10 -2 mol•L -1 . 10 µL of these standard solutions were put into a 2 mL glass vial to evaporate the water under a stream of dry gaseous pure dinitrogen. 30 µL of MTBSTFA and 10 µL of DMF were added to the vial and the derivatization reaction took place by heating the mixture at 75℃ for 30 min [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF]. For the DMF-DMA derivatization, 20 µL of DMF-DMA were added to the vial containing the dried amino acid sample before heating the mixture at 140℃ for 3 min [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]. Derivatization was also performed on alcohol mixtures: 0.1 µL of each alcohol was diluted directly with the derivatization agent (40 µL MTBSTFA/DMF (4:1 mixing ratio); 20 µL DMF-DMA) before the derivatization heating protocol. 0.5 µL of the final solution were injected into the GC-MS.

For the derivatization that was performed directly on a solid natural sample (Section III.3.3.2) spiked with amino acids, 15 µL of DL-serine and DL-alanine, diluted in demineralized water at a concentration of 10 -2 mol•L -1 were added to 15 mg of the natural sample and placed under a stream of dry gaseous pure dinitrogen until complete evaporation of the water. 30 µL of DMF-DMA were then added and the solution was heated at 200˚C for 3 min. The solution was then extracted, with some solid particles in the liquid extract, using a 100 µL liquid syringe (Hamilton) and centrifuged for 1 min to separate the solid and liquid parts. 1 µL of the supernatant was injected to the GC-MS using a 5 µL liquid syringe (SGE).

III.2.1.4. Natural analog sample

Enantiomeric resolution of DL-alanine and DL-serine was studied on a natural analog sample which was spiked with amino acids. The Arctic Mars Analog Svalbard Expedition (AMASE) KitKat sample, a buff-colored carbonate mudstone, was selected as the natural analog sample for this study. This sample is from an environment which has low levels of organic and biological material in mineralogical assemblages as well as a climate relevant to Mars. Carbonates have been found on Mars [START_REF] Ehlmann | Orbital Identification of Carbonate-Bearing Rocks on Mars[END_REF][START_REF] Cull | Concentrated perchlorate at the Mars Phoenix landing site: Evidence for thin film liquid water on Mars[END_REF]) and in martian meteorites [START_REF] Mckay | Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001[END_REF] and are good reservoirs for organics. Even if phyllosilicate-bearing terrains are expected at Oxia Planum, the now selected landing site for the Rosalind Franklin rover, a relevant Oxia Planum analog sample for laboratory testing still remains to be fully constrained [START_REF] Poulet | Modal Mineralogy of Phyllosilicate-and Carbonate-Bearing Terrains from Spectral Modeling[END_REF][START_REF] Quantin | Oxia Planum, The Landing Site for ExoMars[END_REF]) and additional minerals to those seen from orbit are likely to be detected in situ [START_REF] Rampe | Sand Mineralogy Within the Bagnold Dunes, Gale Crater, as Observed In Situ and From Orbit[END_REF]. Additionally, since the objective is to test the capabilities of the MOMA flight spare columns within known MOMA operating conditions, previous MOMA testing on this sample is useful as it has been employed on this same sample [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF].

III.2.2. Laboratory instrumentation

III.2.2.1 Metallic capillary columns

Duplicates of the four MOMA capillary columns were used for this study. Each is one of the two duplicates of each column (three for the Chirasil Dex) purchased in 2013 in the same batch as the flight columns. After their purchase, the columns were tested with a limited number of compounds and the results were used to confirm the good health and performances of the columns during their integration into the flight hardware, and finally to select the ones for the flight and spare models of the instrument. After these tests, the non-selected columns were kept under clean storage conditions. They were plugged and stored in a plastic bag pressurized with pure dinitrogen (99.9999% purity from Linde). The original columns purchased were 25 m long. Due to mass constraints for the space instrument, each column was shortened to 20 m. Characteristics of each column are summarized in Table 7. This combination of four columns was chosen for the purposes of being able to separate a wide range of organic molecules, including i) volatile organic molecules containing 1 to about 25 carbon atoms, ii) organic enantiomers, iii) species produced from derivatization with the three chemical reagents to be used on MOMA, and iv) inorganic volatiles [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. The combination of these four types of columns (i.e., a porous-layered open tubular (PLOT) column, a chiral wall-coated open tubular (WCOT) column, and two general purpose (WCOT) columns fulfilled these requirements, while assuring some redundancy and overlap in their targeted compounds.

III.2.2.2 Gas chromatography mass spectrometry run conditions

The measurements were carried out with a GC Trace Ultra coupled to an Ion Trap Quadrupole (ITQ) MS and a GC Trace Ultra or a GC Trace 1300 coupled to a Single Quadrupole MS (ISQ) (all from ThermoFisher Scientific). The same protocols were used for each instrument. The laboratory work was performed on ITQ/ISQ mass spectrometers, while MOMA will carry a linear ion trap (LIT) mass spectrometer which is a miniaturized version of the ThermoFisher LXQ design [START_REF] Arevalo | Design and demonstration of the Mars Organic Molecule Analyzer (MOMA) on the ExoMars 2018 rover[END_REF]. However, the comparison between MOMA ETU data and laboratory data in Section III.3.4 is sufficient since this current chapter is focused on the gas chromatography parameters, such as retention time and peak shape, which are not affected by any differences between an LXQ and ITQ/ISQ-type design. The laboratory MS data is used for the identification of compounds, which is also sufficient since all compounds which are injected and studied are known standards.

A split/splitless syringe injector (split ratio of 20 or 50) was used to vaporize and transfer the liquid samples to the column with a 0.5 µL or 1 µL volume capillary syringe (SGE), whereas a 1 mL volume gas syringe (SGE) was used to inject gaseous species. The temperature of the injector was 250˚C and the temperature of the GC-MS transfer line was 250˚C to allow the volatilization of all the species studied and their transfer to the MS without any risk of condensation. The laboratory ITQ and ISQ instruments used in this study scanned the ions produced after electron impact ionization of the molecules at 70 eV from m/z 10 to 500. The ionization source temperature was set at 250˚C. The carrier gas was helium (99.999% purity from Air Liquide), the same type of helium which is used in the MOMA FM.

On MOMA, the flow rate is adjustable from 0.8 mL•min -1 to 1.4 mL•min -1 , with a nominal flow rate at about 1.2 mL•min -1 . The initial column temperature can be as low as 30˚C and will be ramped to a final temperature which is dependent on a given column and limited either due to the maximum temperature of use of a column or to the limited amount of energy that can be used for heating. Due to these constraints, the expected MOMA gas chromatographic run duration is about 35 minutes. Because there is adjustability to the parameters of flow rate and column temperature program, it is important to ensure that experiments will be completed in the shortest time possible on Mars without compromising chromatographic performance. For the study of standards on the columns, the GC column was heated from 45-220˚C for the MXT 5 and MXT CLP columns, 45-180˚C for the Chirasil Dex column, and 45-200˚C for the MXT Q BOND column, with a 10˚C•min - 1 ramp in all cases. 220˚C is shown to be the maximum column temperature which can be reached on the FM based on tests performed on a MOMA engineering test unit (ETU) similar to the FM (Section III.2.3). 180°C and 200°C were chosen as the maximum operating temperatures for the Chirasil Dex and MXT Q BOND columns respectively, as they are 20°C lower than the maximum temperature of the columns recommended by the suppliers. This difference was chosen to avoid a premature degradation of the columns' stationary phases. For the study of enantiomeric resolution of chiral molecules, the column was held at 35˚C for 7 min, then heated to 182˚C with a 10˚C•min - 1 or a 3˚C•min -1 ramp. The column temperature programs used in our tests are shown in Figure 25.

Table 8: Technical parameters of GC-MS analysis between the FM and in the laboratory. Derivatization-GC-MS parameters only are given here, since pyrolysis-GC-MS has not been studied in this work. However, it is expected that the maximum temperature of the pyrolysis ovens will be 800 to 850˚C [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]

III.2.3. Relevant tests on MOMA ETU and FM

The laboratory tests described in the first part of this chapter were performed on a commercial GC-MS system with a hand-held syringe injection. Section III.3.4 of this chapter is dedicated to a comparison of the laboratory tests with tests that were performed on a MOMA ETU experimental setup. The ETU testing campaign that will be referred to in this chapter is a GC-MS coupling campaign at the NASA Goddard Spaceflight Center (GSFC) on an ETU in 2018 [START_REF] Kaplan | Demonstration and verification of the pyrolysis and derivatization GCMS capabilities of the Mars Organic Molecule Analyzer (MOMA) Mass Spectrometer[END_REF], and referred to as the ETU tests. I was not physically present during these tests, but rather assisted in supportive pre-campaign laboratory testing and post-campaign data analysis and interpretation.

The MOMA team members who organized and implemented the campaign are named in the Acknowledgements section of this chapter. Important differences between the laboratory and an ETU/FM scenario include the method of sample injection, transfer line temperatures, and the gas sample processing system. On MOMA, injection traps (IT), based on the principle of thermal desorption, allow direct transfer of compounds to the column. Trapped chemical species are released from the IT to the chromatographic columns by rapid heating (Figure 26) to enable sufficiently short injection times [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]). In the laboratory, injection is completed manually with a hand-held microliter-volume syringe. A comparison of chromatographic peak behaviors between syringe injection and injection trapping using laboratory and ETU data are further explored in Chapter V (Section V.4.2.2). Figure 26 shows a plot of the IT heating profile from thermal-vacuum tests on the FM performed at the Thales Alenia Space Italia (TAS-I) in 2019, referred to as the FM-TAS-I tests. Two major objectives of the coupling campaign were demonstration of ( 1) the separation and detection of chiral compounds, since this is a key functionality for the search for life, a main goal of the ExoMars mission, and (2) the analysis of complex martian analog samples in a simulated "day-in-the-life" of the MOMA experimental setup [START_REF] Kaplan | Demonstration and verification of the pyrolysis and derivatization GCMS capabilities of the Mars Organic Molecule Analyzer (MOMA) Mass Spectrometer[END_REF]. This section will focus on the first objective, that of chiral separation and detection of chiral compounds. Therefore, the selection of chemical standards included chiral molecules of three types (chiral amino acids, chiral alcohols, and a chiral alkane). In addition to chiral molecules, carboxylic acids (decanoic acid, palmitic acid) were also tested, since carboxylic acids represent important target molecules of martian astrobiology as described in Section III.2.1.1.

The carrier gas flow is controlled by a PCV valve, which is temperature controlled so that heating of the valve causes the valve to be more or less open as a function of the temperature. A correlation was experimentally determined between the valve temperature and the flow rate measured at the end of the column in order to control the helium flow during testing. Derivatization was performed in three forms to test each step of the process in a progressive way in order to identify potential instrumental issues:

(1) Offline on a benchtop oven at ~140˚C for 3 minutes before syringe injection of the derivatized chemical species to the ETU. In this case, only the evaporation and transfer of the derivatized species to the GC-MS is tested and the derivatized species can be analyzed on a laboratory instrument to confirm that the derivatization reaction worked well. This is a kind of best case in this series of experiments. (2) Online without a MOMA derivatization capsule to check if the derivatization process can occur directly in the oven without any bias. A comparison with the results obtained with the previous step allows to control the efficiency of the reaction and transfer. For these experiments, solutions of amino acids and carboxylic acids were deposited onto a square of aluminum foil and left to evaporate before placing the aluminum foil in the ETU oven. DMF-DMA was added by syringe injection to a "closed system" for the derivatization reaction and then the valve/line was opened to the trap, He flushed the oven, and the oven was heated to a higher temperature as shown in Figure 29. For the solid samples, milligrams of sample were placed in a Frontier pyrolysis cup, which was capped with quartz wool, before being placed inside the oven prior to the reagent injection by syringe. (3) Online with a MOMA derivatization capsule to test the flight case. This third type of derivatization tests are not fully described here since the results of those tests are not covered in this thesis.

III.2.3.3. Data Analysis Tools

Data analysis of MOMA ETU data was performed in momadataview, a software developed internally by a portion of NASA/GSFC-affiliated members of the MOMA team. A description of the software is beyond the scope of this work but it can be said that it includes all the regular functionalities of commercial software used to display and manipulate the analytical data (e.g., display chromatograms, mass spectrum at a given time of analysis, etc.). In addition, the software allows the display of housekeeping data which are key to treatment of the GC-MS signal. For calculations of peak area for a given compound, intensities of each mass fragment which have ≥10% of the intensity of the major m/z peak according to the NIST standard were measured or calculated, summed and background subtracted.

III.3 Results and Discussion

III.3.1 Column efficiency

On MOMA, the flow rate is adjustable from 0.8 mL•min -1 to 1.4 mL•min -1 . The initial column temperature can be as low as 30˚C and will be ramped to a final temperature which is dependent on a given column (220˚C for the MXT 5 and MXT CLP, 200˚C for the MXT Q BOND and 180˚C for the CP Chirasil Dex) and limited either due to the maximum temperature of use of a column, or to the limited amount of energy that can be used for the heating. The column temperature ramp can be as low as 1˚C•min -1 and not higher than 15˚C•min -1 , although after a column temperature of 180˚C the ramp is no longer fully constant when using a 15˚C•min -1 ramp. A nominal initial temperature of 30˚C, a ramp to a final temperature determined by the column, and then a temperature plateau for ~10 min are the expected column temperature operations for Mars.

Because there is adjustability to the parameters of flow rate and column temperature program, it is important to ensure that experiments will be completed in the shortest time possible (conservation of resources) without compromising chromatographic performance prior to performing gas chromatography experiments with MOMA on Mars. The flow rates chosen for our study, roughly 0.2 mL•min -1 to 2 mL•min -1 , and the GC column temperature programs (Figure 25) are consistent with the adjustability on MOMA.

The carrier gas velocity is a key parameter, as it affects a column's efficiency in resolving chromatographic peaks. Optimizing mobile phase velocity can dramatically decrease the time needed to complete an analysis, a key requirement of space experimentation. The optimum mobile phase velocity for each of the four MOMA chromatographic columns was determined by investigating the minimum height equivalent to a theoretical plate (HETP). The HETP was determined as

HETP = L/N Equation 2
where L is the column length and N is the number of theoretical plates, calculated as

$ = 5.54 ) !R "h * # Equation 3
where tR is the retention time of a given solute and wh is the width at half height of the chromatographic peak. The dead time was measured using an injection of air, which was injected separately from the other compounds under the same operating conditions.

The evolution of HETP was studied as a function of the carrier gas velocity for 1-butanol, DLalanine, and chlorobenzene for the MXT 5, MXT CLP and Chirasil Dex columns, and ethanol for the MXT Q BOND column. The chlorobenzene was diluted in ethanol and was not derivatized, the 1-butanol was diluted in acetone and was not derivatized, the ethanol was diluted in methanol and was not derivatized, and the DL-alanine was derivatized by DMF-DMA. These compounds were selected to be representative of different chemical families, as compounds of interest for Mars surface science, and as having a wide range of retention properties. Instrument flow rate was varied so as to correspond to a helium velocity range of 40 to 80 cm•s -1 , depending on the laboratory instrument used. Two isothermal temperature conditions were used for 1-butanol and chlorobenzene, 60˚C and 120˚C. Alanine was studied at 115°C in order to observe the efficiency behavior across different temperatures [START_REF] Millan | Influence of Calcium Perchlorate on Organics Under SAM-Like Pyrolysis Conditions: Constraints on the Nature of Martian Organics[END_REF].

Figure 30 and Figure 31 show the evolution of the HETP as a function of linear carrier gas velocity for all of the spare MOMA GC columns. A polynomial function was used to fit the efficiency curves. Most curves show behavior consistent with the usual behavior of HETP with linear gas velocity, namely an inverse function describing the longitudinal diffusion term at low gas velocities and a linear function describing the mass transfer term at high gas velocities. The hyperbolic behavior of the curve is such that HETP achieves a minimum value at a particular linear gas velocity. These velocities, at which the resolving power of the column is theoretically maximized, are tabulated in Table 11.

All four columns had similar ranges of optimal carrier gas velocities. There was some variation in the minimal HETP displayed when the column was held at different temperatures. For example, with the Chirasil Dex column, a minimal HETP was obtained at 67 cm•s -1 for 1-butanol run isothermally at 60℃, for which the efficiency curve was rather flat at low gas velocities, while 55 cm•s -1 was obtained for 1-butanol run isothermally at 120℃ (Figure 30). In general, 1-butanol displayed a minimal HETP at higher gas velocities than chlorobenzene, with the exceptions of the MXT CLP column and the Chirasil Dex column heated at 120˚C, in which the minimal HETP for 1-butanol was at lower gas velocities than for chlorobenzene. The stationary phase of the MXT CLP column may slightly limit its efficiency compared to columns bonded with polydimethylsiloxane and phenyl, e.g. the MXT 5 column, for chlorohydrocarbons. However, the MXT CLP column was the most efficient column in separating the amino acid, DL-alanine. Additionally, the MXT CLP column efficiency curves are rather flat, especially for chlorobenzene, another phenomenon which has been observed for chlorohydrocarbons at higher gas velocities [START_REF] Millan | Influence of Calcium Perchlorate on Organics Under SAM-Like Pyrolysis Conditions: Constraints on the Nature of Martian Organics[END_REF].

The FM-TAS-I tests had a measured dead time between 0.53 and 0.87 min (Figure 26) using the MXT 5 column, which corresponds to a linear gas velocity of ~38 to 63 cm•s -1 . This ambiguity in dead time for MOMA due to the heating temperature profile is problematic for confirming compatibility between FM operating conditions and optimal velocities, as such a velocity range corresponds to much of the profile of the HETP curve. If the dead time is nominally calculated from the beginning of the trap heating, since dead time is measured from volatile compounds that are readily released from the trap as soon as heating begins, the gas velocities measured for the FM-TAS-I tests would be around 40 cm•s -1 , which corresponds to an HETP value of around 0.08 cm for high temperatures, much higher than the optimal 0.04 to 0.06 cm HETP values found at higher gas velocities.

III.3.2 Separation power of selected standards

A number of chemically diverse compounds (Table 6) were targeted and tested on a laboratory GC-MS under constrained operating conditions imposed by the limitations of the space experiment. Alkanes, alcohols, carboxylic acids, and amino acids were tested on each of the appropriate spare MOMA GC columns. The retention time, or the time for each solute to pass through a given chromatographic column, of each compound by chemical family and by GC column are catalogued in Table 12 (Chirasil Dex, MXT 5 and MXT CLP columns) and Table 13 (MXT Q BOND column) and are also described pictorially in Figure 37. This type of retention time library allows for an examination of the capability of the chromatographic column suite as a package to achieve the needed separations under MOMA-like operating conditions. The following sections develop with more details the performances of each chromatographic column.

III.3.2.1 MXT Q BOND

The MXT Q BOND column is dedicated to the separation of the lightest compounds including the noble gases and the smallest hydrocarbons. Although it cannot be expected to elute any compound above a C6 carbon chain with this column in a nominal 35-minute run time, it will be possible to clearly separate lighter organic compounds and even inorganic gases which are permanently gaseous under martian atmospheric conditions. Although the scientific priority of MOMA will be the detection of organic molecules in solid samples, our tests show that the noble gases can be successfully separated on the MXT Q BOND column (Figure 32) using a lower carrier gas flow rate (1.0 mL•min -1 ) and the ETU temperature program (Figure 26). This is an example of additional science, e.g. in situ isotope measurements of noble gases in the martian atmosphere [START_REF] Conrad | In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory[END_REF], that can be successfully completed using the MOMA chromatographic column package with a modified column temperature program within the adjustability of MOMA. 3) is related to the retention time of each enantiomer. The efficiency of each column was studied at 60℃ and 120℃ for 1-butanol and chlorobenzene, to represent a range of operating temperatures to be used in flight, with the exception of the Q BOND column. The efficiency curve for DL-alanine was studied at 115℃ since its retention time on the three columns, MXT 5, MXT CLP, and Chirasil Dex, was too high for tests using a lower isothermal hold, i.e. 60˚C. Ethanol was studied at 115℃ to characterize the efficiency of the MXT Q BOND.

III.3.2.2 MXT 5 and MXT CLP columns

The MXT 5 and MXT CLP columns were selected for the separation of organic compounds that contain up to about 25 carbon atoms (depending on their chemical nature). The number of compounds targeted by these columns is significant and the opportunity for overlap of a compound of interest with another peak coming from the martian sample and/or from derivatization products and byproducts is likely, given the complexity of most chromatograms from natural samples. Therefore, the use of two columns limits the risk of non-identification of such species (Szopa et al. 2002(Szopa et al. , 2003)). Moreover, most of the compounds expected to be detected should be analyzed with these columns. Their capability to separate the same range of compounds is therefore a key instrumental redundancy in the case that the performance of one of these columns is degraded through time on Mars. Figure 37 illustrates how the retention times across families of molecules on each of these two columns is very similar, yet staggered, increasing the likelihood of detecting compounds of interest and creating redundancy within the GC subsystem.

Figure 33 shows C7-C29 alkanes (up to C40 were injected) detected on the MXT 5 column within the 35-minute GC run time. An expected significant peak broadening is observed with increasing retention time, due to increased longitudinal diffusion inside the column. This broadening with increasing molecular weight has consequences for the detection limit of higher molecular weight compounds. In tests performed on the MXT CLP in which C7-C40 alkanes were injected, up to a C30 alkane was visible above background at a retention time of about 40.10 min (longer than a nominal MOMA run) before the signal was no longer resolvable from the background signal. Our tests demonstrate a best-case scenario in terms of the maximum carbon number (in this case, for alkanes) that will be detectable by MOMA. First of all, the GC temperature ramp starts immediately with no isothermal hold at the beginning of the run; conversely, on MOMA and flightlike setups such as the ETU, there is an isothermal hold of at least 1-5 minutes at the beginning of the GC run, both to elute non-and poorly-retained compounds and to accommodate time for trap cooling/flow path changes prior to the start of the ramp. In addition, it has not yet been systematically characterized how differences in the operating temperatures (e.g. line temperature differences) and gas processing systems between the FM and the laboratory will affect the maximum carbon number expected to be visible with MOMA. 1) heptane, (2) octane, (3) nonane, (4) decane, ( 5) undecane, (6) dodecane, (7) tridecane, (8) tetradecane, (9) pentadecane, (10) As described in the introduction, compounds that contain a labile polar functional group, such as the alcohols, amino acids, and carboxylic acids, require derivatization in order to be reliably identified by a GC-MS system. Based on the relative retention time results for these three families of compounds (Figure 37), the MXT CLP column appears to have a more polar stationary phase, since molecules with higher polarity such as the pure alcohols are slightly more retained by the Intensity (cps)

MXT CLP than for the MXT 5 column. Additionally, the alkane group, with the least polarity, is retained by the stationary phase of the MXT 5 slightly longer than for the MXT CLP. When molecules (i.e. alcohols, carboxylic acids, amino acids) are derivatized and become less polar, the compounds often elute first from the MXT CLP column, meaning they experience a weaker interaction with the stationary phase.

C3 to C8 linear alcohols were injected and were detected in their pure, DMF-DMA derivatized, and MTBSTFA derivatized forms. Figure 34 shows a comparison between the retention times of pure alcohols and with MTBSTFA derivatization on the MXT CLP column and pure alcohols separated by the MXT Q BOND column. This comparison illustrates two important components of the gas chromatography analysis. First of all, when derivatization is performed, especially in the case of MTBSTFA derivatization in which a silyl group (Si(CH3)2C(CH3)3) replaces any labile hydrogen, the mass of the compound can increase substantially. This accounts for the higher retention times of derivatized compounds in Figure 34 on the MXT CLP column and will be an important consideration when adjusting for GC run time during derivatization runs on Mars. It is particularly interesting for the case of the derivatized alcohols because the retention time for alcohols derivatized with MTBSTFA versus with DMF-DMA is quite similar for the MXT 5 and MXT CLP columns (Figure 37). This suggests that the DMF-DMA derivatized alcohols are not merely undergoing a methylation, but rather a dimethylformamidination or another closely related reaction, causing the mass of the parent alcohol molecule to increase proportionally to the mass of an added silyl group. This example illustrates the importance of understanding the potential mass spectral library for MOMA surface science in addition to the retention time library fully described in this chapter. Secondly, a comparison between alcohols separated by the MXT CLP, a WCOT column, and the MXT Q BOND, a PLOT column, shows the expected higher retention times produced by a PLOT column compared with a WCOT column since PLOT columns have a thick porous layer of adsorbent attached to the column walls which increases the amount of time in which compounds interact with the stationary phase. In Figure 34, the decreasing baseline level is due to peak broadening with increasing retention time, due to increased longitudinal diffusion inside the column.

All of the studied derivatized aromatic and aliphatic carboxylic acids were detected (up to hexadecanoic acid (palmitic acid), m/z 256), except mellitic acid (m/z 342). While the molar mass of hexadecanoic acid is about 256 g•mol -1 , it has only one carboxylic acid function, while mellitic acid has six carboxylic acid functions (Figure 35). Therefore, mellitic acid has six additional tertbutyldimethylsilyl groups added after derivatization with MTBSTFA, which leads to a molecular mass of 1026 g•mol -1 . This explains the non-detection of mellitic acid in comparison to the detection of hexadecanoic acid within the nominal MOMA GC run time. Given the elution time of hexadecanoic acid on the MXT 5/CLP and the Chirasil Dex columns, it is likely that a linear carboxylic acid with a molecular mass of around 340 g•mol -1 and only one labile hydrogen, corresponding to a molecular mass of only around 454 g•mol -1 after MTBSTFA derivatization, would be visible within the nominal MOMA GC run time. Although the run time did not allow the detection of mellitic acid, several potential byproducts of mellitic acid were observed after derivatization by DMF-DMA on the MXT 5 column, e.g.

III.3.2.3 Chirasil Dex column

The same molecular weight compounds cannot be retrieved with the Chirasil Dex column, in comparison to the MXT 5/CLP columns, since the maximum operating temperature allowed for the integrity of the column's stationary phase is lower. However, the Chirasil Dex column has the obvious added value of enabling enantiomeric separation. Enantiomeric resolution of amino acids and other chiral molecules are studied on the MOMA chiral column in more detail in Section III.3.3. Additionally, the Chirasil Dex column appears more polar than either the MXT CLP or the MXT 5, since polar compounds such as the pure alcohols have the longest retention times of these three columns. Therefore, this column will also have better separation of more polar molecules.

The retention times for derivatized carboxylic acids are higher on the Chirasil Dex column than the MXT series for both MTBSTFA and DMF-DMA derivatization. The molecules have become less polar after derivatization, but it appears that other physical and/or chemical interactions between these specific kinds of molecules, i.e. amino acids and carboxylic acids, and the stationary phase of the Chirasil Dex column are also important. All of the injected derivatized amino acids were detected (i.e. DL-serine, DL-alanine, glycine, DLvaline, DL-leucine, and DL-glutamic acid). The chiral enantiomers of L-D-serine, D-L-alanine, and D-L-valine were separated under run conditions similar to those performed during the ETU tests (Figure 36). The -COOH group of the amino acid is methylated while the amine group undergoes dimethylformamidination during the DMF-DMA derivatization reaction. Additional derivatization can also occur on -OH groups attached to the side chain. An example of this is DLserine, which has an additional hydroxyl group and therefore will undergo additional derivatization. The MTBSTFA-derivatized serine will undergo trisilylation, which has a clear effect on the final molecular weight of the compound and its retention time (Figure 37). The later retention times of derivatized amino acids on the Chirasil Dex as compared to those on the MXT series is not as pronounced as for other molecules, with the exception of DL-serine, likely due to its polar quality and its resulting derivatization process.

III.3.2.4 Combined effectiveness of MOMA chromatographic column package

A full table of retention times is shown in Table 12 (Chirasil Dex, MXT 5, MXT CLP) and Table 13 (MXT Q BOND). The separation domains of the columns overlap and most of the targeted

OH O O O O O O O H O O O (H 3 C) 3 C(H 3 C) 2 Si Si(CH 3 ) 2 C(CH 3 ) 3 O Si(CH 3 ) 2 C(CH 3 ) 3 (H 3 C) 3 C(H 3 C) 2 Si CH 3 O O (H 3 C) 3 C(H 3 C) 2 Si DMF R O O H + CF 3 N O CH 3 Si(CH 3 ) 2 C(CH 3 ) 3 R O O Si(CH 3 ) 2 C(CH 3 ) 3 + CF 3 N O CH 3 H MTBSTFA-derivatized mellitic acid Carboxylic acid Volatile product MTBSTFA-derivatized palmitic acid Si(CH 3 ) 2 C(CH 3 ) 3 (H 3 C) 3 C(H 3 C) 2 Si 75˚C
volatile species are detectable by the GC column package, demonstrating the system to be efficient for the separation of compounds in the same mass range than those originally targeted by MOMA. Figure 37 illustrates the overlapping separation domains of the GC column package with a cartoon that visually summarizes the spread of retention times of targeted compounds across a 35-minute run time. Species identification by the flight chromatograms will require the availability of this type of database and likely will require iterations on systematic laboratory tests such as this one. These tests do not consider the capabilities of the MOMA hydrocarbon traps, which may limit heavier molecules from ever reaching the column, since the temperature controls of the hydrocarbon traps can be optimized to adsorb/desorb compounds within a specific range of number of carbon atoms. Molecules which are not desorbed from the hydrocarbon trap during injection may still be detected by the MOMA LDMS. If preliminary biomolecules are detected on Mars, flight and laboratory GC-MS runs will inform the trade space on whether to modify the GC run conditions in order to target higher molecular weight compounds. Conversely, if the team wants to focus on the separation of small molecules, the temperature ramp could be decreased. 12 andTable 13.

In addition to eluting across a range of retention times, the types and families of molecules were chosen in order to assess the separation of important compounds for MOMA's science objectives which include testing for bioindicators and biosignatures. For example, many important biochemicals exist in discreet molecular weight ranges (e.g., C14-C20 lipid fatty acids). Whereas the relative abundance for abiotic volatiles in cosmic carbon chemistry is uniform and drops off as the carbon number increases [START_REF] Ehrenfreund | Cosmic Carbon Chemistry: From the Interstellar Medium to the Early Earth[END_REF][START_REF] Ehrenfreund | Organic Molecules in the Interstellar Medium, Comets, and Meteorites: A Voyage from Dark Clouds to the Early Earth[END_REF], the molecular weight distribution of biologically-derived matter is concentrated in discreet clumps corresponding to the various life-specialized families of molecules [START_REF] Summons | Molecular Biosignatures[END_REF].

Additionally, many biological products (e.g., proteins and nucleic acids) are synthesized from a limited number of simpler units. An identifiable molecular weight signature could be recovered in fragments from highly derived products, since classes of biomolecules can exhibit characteristic carbon chain length patterns. For example, C15, C20, C25 carbon chain length patterns are constructed by acyclic isoprenoids using repeating C5H10 subunits or C14, C16, C18, C20 carbon chain length patterns are constructed by enzymes synthesizing fatty acids in C2H4 subunits [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF]). This study suggests that the combination of pyrolysis and derivatization-GC-MS techniques on MOMA could enable the detection of C29 straight-chain alkanes, C20 straight-chain alcohols, as well as C18 to C20 straight-chain carboxylic acids, and C8 or C10 amino acids, depending on the derivatization reagent and number of labile hydrogens. The MOMA gas An assortment of proteogenic amino acids can be detected with the chromatographic column package, and the column package enables multiple kinds of biosignature detection, including amino acid enantiomeric excess (Section III.3.3) and the relative abundance of types of amino acids. Biotic and abiotic processes on Earth can produce distinctly different amino acid (and lipid hydrocarbon) mixtures. Terrestrial life is selective, using a limited subset of molecular building blocks to construct larger, more complex biomolecules in order to meet physiological needs [START_REF] Ehrenfreund | Extraterrestrial amino acids in Orgueil and Ivuna: tracing the parent body of CI type carbonaceous chondrites[END_REF][START_REF] Eigenbrode | Fossil Lipids for Life-Detection: A Case Study from the Early Earth Record[END_REF][START_REF] Summons | Molecular Biosignatures[END_REF]. In contrast, abiotic processes favor random synthesis of smaller, simpler molecules [START_REF] Davila | Chance and necessity in biochemistry: implications for the search for extraterrestrial biomarkers in Earth-like environments[END_REF][START_REF] Georgiou | Lipids as Universal Biomarkers of Extraterrestrial Life[END_REF]. If subsurface Mars is sterile, amino acids and lipid hydrocarbons are still expected to be present given their abundance in meteorites, comets, synthesis products of hydrothermal reactions, and predicted products of organic chemistry models. The ability of the MOMA gas chromatographic column package to test multiple parameters (e.g., relative abundance of amino acids, enantiomeric excess, patterns in lipid hydrocarbons, chain length distributions as a function of carbon number) enables a confidence value to any potential biosignature detection [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF].

III.3.2.5 Comparison with Curiosity's SAM

Based on the vast experience of the Curiosity rover's SAM instrument, MOMA was designed to support the detection of higher mass compounds within chemical families of interest. The flow is ) and the GC columns on SAM are longer, resulting in more retained compounds with longer retention times. For example, of the amino acids, only glycine and alanine are visible within SAM conditions from laboratory experiments, while the MOMA run conditions allow for the detection of serine, valine, leucine, and glutamic acid in addition to glycine and alanine. On the alkane side, dodecane takes 18-20 min to elute from the SAM columns, while here the retention time of dodecane for MOMA would be between 5-8 minutes depending on the MOMA column [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF]. This comparison offers an exciting prospect for MOMA's capability to detect high molecular weight compounds of interest on Mars.

III.3.3

Laboratory testing of the enantiomeric capability of MOMA's chiral column

III.3.3.1 Separation power

The MOMA instrument has the unique capability to detect and separate molecular enantiomers. The quantification of enantiomeric excess could reveal information about whether martian molecules are racemic or if they express an enantiomeric bias as is observed in terrestrial biomolecules. Therefore, it is paramount that a combination of the flight hardware, i.e. the gas chromatographic columns, the wet chemistry protocol, and the in situ operating conditions of the flight experiment, be shown to successfully separate chiral molecules into their enantiomers. The resolution of both enantiomers, RS, is used to characterize the degree of separation of two enantiomeric peaks, where: RS = 1.8•(tRB-tRA)/(+A++B) Equation 4RS, the enantiomeric resolution, depends on two parameters, the time separating the two peaks (thermodynamic factor), tRB-tRA, and the width of each of the two peaks (kinetic factor), +A++B.

The enantiomeric resolution of three types of chiral compounds are tested: an alkane (3methylheptane), underivatized alcohols (2-butanol, 2-pentanol, and 2-hexanol) and DMF-DMA derivatized amino acids (DL-serine, DL-alanine, DL-valine, DL-leucine, and DL-glutamic acid) as a function of the carrier gas velocity which moves solutes through the GC column.

The range of carrier gas velocities utilized for the study of enantiomeric resolution, and plotted in Figure 38 (~40-80 cm•s -1 ), corresponds to a range in dead time (the time for a non-retained compound to travel through the column) of ~0.45-0.85 min, consistent with the expected dead times on MOMA (Figure 26). Figure 36 shows the enantiomeric separation of L-D-serine, D-Lalanine, and D-L-valine on the MOMA spare chiral column and Figure 38 shows the enantiomeric resolution of all the chiral compounds that were tested in this study. "Mid-range" (55-60 cm•s -1 ) to "low" (35-55 cm•s -1 ) helium velocities are optimal for enantiomeric resolution. For the alcohols, there is a decrease in resolution also at "low" flow rates (below ~55 cm•s -1 ) with the exception of 2-butanol. Baseline separation (separation at or below half-height-half-width of the chromatographic enantiomeric peaks) is achieved for most of the chiral compounds using a column temperature ramp of 10˚C•min -1 , a ramp which will allow for detection of higher molecular weight compounds within a given run time.

However, for the amino acids, baseline separation was achieved with a 10˚C•min -1 column temperature ramp only for DL-alanine and DL-serine. A lower temperature ramp, 3˚C•min -1 , was employed, since lower temperature ramps have been shown to successfully separate amino acids after optimization on a longer (30 m) Chirasil Dex column [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]). This lower temperature ramp allowed for baseline separation of an additional amino acid in our test set, DLvaline. Valine was not separated to half-height-half-width with the higher ramp rate, 10˚C•min -1 . The optimization of enantiomeric separation is a tradeoff with run time, as the slower ramp requires longer run times and more resources from the spacecraft. MOMA has the capability to decrease its GC column temperature ramp as low as 1˚C•min -1 . However, the implications of a lower ramp are that heavier molecules may not be detected during the run time.

III.3.3.2 Enantiomeric separation on natural sample

A martian analog sample was tested on the MOMA chiral column to demonstrate GC separation and identification of selected spiked amino acids in the presence of a complex mineral phase. As with the study of standards, the aim is to test GC separation under conditions similar to that of the MOMA experiment without mimicking the entire process. For example, the derivatization is performed in an oven external to the GC-MS instrument and then injected the derivatized sample by syringe injection, while for MOMA, the sample is heated within the oven until the derivatization reagent is released at a given temperature. However, the use of an analog sample allows the analysis of a more realistic gaseous mixture than those produced with chemical standards. Additionally, it is shown that the influence of the mineral phase does not limit the ability to detect certain organic molecules such as amino acids if they are present at a certain concentration in the sample. The natural sample used in this study was spiked with amino acids, so that the amino acids were partially adsorbed to the sample's mineral matrix. On MOMA, thermal desorption performed on the sample prior to the release of the derivatization reagent will aid extraction of organics adsorbed on mineral surfaces and/or within interlayer spaces [START_REF] Buch | Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results[END_REF][START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. The derivatization temperature of 200˚C is consistent with the 175˚C temperature used during the AMASE campaign on the same sample [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF]. A higher temperature is selected for the laboratory tests in order to procure a more efficient extraction of organics, but low enough to safeguard against decomposition of the derivatization reagent.

Figure 38: Enantiomeric resolution of selected compounds vs. carrier gas linear velocity. 2-butanol and 3methylheptane were not separated to baseline at the highest carrier gas velocity. The chiral alcohols and 3methylheptane in this study are not derivatized while the amino acids are derivatized with DMF-DMA. The GC column was heated from 45˚C to 180˚C with a 3˚C•min -1 ramp for the amino acids and the GC column was heated at 35˚C for 7 min and ramped to 182˚C at a ramp rate of 10˚C•min -1 for the chiral alcohols and the 3-methylhexane.

Figure 39 shows the separation of enantiomers after DMF-DMA derivatization within a more complex natural sample. Comparing the enantiomeric behavior in Figure 36 and Figure 39 illustrates the appropriateness of analog samples for limit of detection studies due to the more realistic noise levels. It is the expectation to see peaks from other organic molecules indigenous to the sample, in addition to the spiked amino acids, since the AMASE KitKat sample was previously determined to contain low amounts of aliphatic and aromatic organic material after GC-MS pyrolysis and derivatization [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF], although the enantiomers of amino acids indigenous to the sample have not been successfully separated. The chromatograms in Figure 39 illustrate the value of GC-MS instrument coupling for strict identifications of targeted compounds on these more realistic samples. On the chromatographic side, additional peaks with the same important ion fragments (i.e. m/z 70 and m/z 99) are prevalent in the single ion mode, sometimes at higher abundances than the targeted molecules themselves. On the mass spectrometry side, the occurrence of co-eluting peaks interferes with discreet mass spectral signatures and definitive identification by spectral libraries. The identification of DL-serine and DL-alanine were made using specific peak ions (m/z 70 and m/z 99 respectively) coupled with the known retention time of DL-serine and DL-alanine (measured by chemical standard in Section III.3.2) which allows for the strict identification of these targeted chemical species. This exercise demonstrates the utilization of retention time libraries such as the one described in this chapter in order to make identifications within more complex samples.

III.3.4 Comparison of laboratory and MOMA ETU tests

This section will compare the laboratory data presented in the previous part of this chapter with tests that were run on a MOMA ETU during the 2018 GSFC ETU tests.

III.3.4.1 Dead time determination for MOMA ETU

The dead time for a chromatographic column is equal to the time is takes for an unretained compound to move through the length of the column. The theoretical value can be calculated and can be obtained experimentally using the first chromatographic peak visible in a chromatogram (e.g. air). This experimental peak is very important in the case of comparing analyses between different GC-MS systems. Independently of the instrumental methods for indicating flow rate, these two values can be directly compared between the ETU and laboratory data in order to justify the similitude of the chromatographic parameters between the systems and the validity of comparing retention time results, since the retention time is impacted in part by the column flow rate.

On the MOMA FM, the MOMA injection trap is heated for at least 10-15 s in order to release organics adsorbed onto the trap material [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. Therefore, there is a minimum 10-15 s interval ambiguity to the exact injection time of a given compound. During the ETU tests, the injection trap was heated from 0˚C to about 250˚C in about 40 seconds and held at about 250˚C for about 10 seconds before cooling. The trap temperature curve which was used in the 2018 ETU tests is plotted in Figure 40 (left panel). Since the injection is not instantaneous, there is a question as to where the injection time should be taken in order to calculate the dead time (tM) and to experimentally confirm the carrier gas velocity. Taking the start of the trap heating as t0 is supported by the fact that most volatiles will be released at the lower end of the trap heating profile and dead time is measured from highly volatile compounds that should be readily released from the trap as soon as heating starts. On the other hand, because of the slow heating of the trap, there is some delay in the release of higher molecular weight compounds from the trap. However, this should be somewhat compensated for by the fact that the compounds will elute when the GC column is already heated to a higher temperature. A second option is to use the completion of the trap heating as the injection t0, which shows a better match to retention times of the same compounds measured in the laboratory on MOMA flight spare columns assuming the same flow rate. Here retention times are presented based on taking the start of the trap heating as t0 for the sake of consistency, but retention times for both cases are calculated and compared to lab values under similar conditions when available. Another challenge in this data for the experimental calculation of dead time is selecting the appropriate unretained compound in the run. There are many parameters in the experimental implementation that can modify the theoretical value of the dead time, including the timing of events during the experiment, changes in flow rate and system temperatures, whether or not the oven or trap is bypassed, and which trap (i.e., Trap 1 or Trap 2) is utilized. The mass range for MOMA is nominally 50-500 Da. However, the ETU system is capable of going beyond this range at each end. In the ETU tests, the MS scanned as low as m/z 34. Therefore, water (m/z 18) and air (m/z 28) signals, used as diagnostic signals in laboratory GC-MS analyses, are not visible. CO2 (m/z 44) has been selected as a reference compound for the unretained compound across tests.

Examples are plotted in Figure 40. However, CO2 may not be the appropriate reference for every run. For example, CO2 is not clearly present in every run: signals for m/z 44 may be due to a contributed ion from another species other than CO2 eluting from a previous run or are hidden by other species of higher abundance, a phenomenon intrinsic to ion trap MS. Figure 40 shows an example of a case in which large peaks of m/z 45 and 61 appear before a major peak of m/z 44 or are masking a CO2 peak from visibility.

III.3.4.2 Comparison of retention time between laboratory instrumentation and MOMA ETU

A set of selected chemical standards were tested on the ETU (Table 9), including chiral alcohols, 3-methylhexane, DL-serine, decanoic acid, and hexadecanoic acid. In this section, retention times between the laboratory (Section III.3.2) and the MOMA ETU tests are compared. The flow rates and temperature programs are different between the chiral alcohols run on the ETU and in the laboratory, and so are not directly compared. The chromatograms are plotted in Figure 41 along with the column temperature curve to show the differences in GC conditions for the tests of chiral alcohols between the laboratory and the ETU.

The retention times of standards run in the laboratory and in ETU tests are given in Table 14 along with the temperature of the column at a given retention time. Figure 42 and Figure 43 show retention time comparisons of 3-methylhexane and D-L-serine between the laboratory and ETU tests. Retention times are compared here, while chromatographic peak behavior is discussed in the following sections, including peak shape and peak width (Section III.3.4.3) and enantiomeric separation and enantiomeric resolution (Section III.3.4.4).

Figure 42 shows a more consistent retention time between the lab and ETU tests of 3-methylhexane based on an injection time at the maximum of the trap heating under the same column temperature conditions. Enantiomeric separation of 3-methylhexane is not observed under these GC conditions, which is further discussed in the following section (Section III.3.4.3). However, the dead time for the lab test is 0.6 min or 36 seconds, lower than the estimated experimental dead time for the ETU case of ~50 seconds to 1 min. If the flow rate in the lab experiment is higher than in the ETU experiment, this could explain the shorter retention time in the lab experiment. Additionally, the ETU isothermal hold temperature was slightly higher (37˚C) than in the laboratory (35˚C) which would result in a comparative decrease in retention time in the ETU test. Therefore, the retention times in the laboratory and ETU tests are consistent with each other. However, the peaks in the ETU tests are broader than the peaks in the laboratory tests, which cannot be explained only by the difference in retention time but is also due to the injection method. A comparison of peak behavior is discussed in the following section (Section III. 3.4.3). 1,2), 2pentanol [START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF]4), and 2-hexanol ( 5) on the MOMA Chirasil Dex column on the MOMA ETU. These results are not quantitative since these peaks were observed in a subsequent blank test following a test in which 20 nL of an equivolumetric mixture was injected to the ETU system, which was not used due to saturation of the GC column with this injection volume. The 2-hexanol chemical standard was in its L-enantiomeric form only, while the 2-butanol and 2-pentanol chemical standards are racemic mixtures. The column was heated at 40˚C (held for about 3 minutes) and then heated up to 180˚C at a rate of about 9˚C•min -1 . (Bottom) Chromatogram of a similar mixture of 2-butanol (1,2), 2-pentanol (3,4), and 2-hexanol (5,6) in the laboratory on a COTS GC-MS with the MOMA flight spare Chirasil Dex column. The column was heated at 35˚C (held for about 7 minutes) and then ramped to 182˚C at a rate of 10˚C•min - 1 . The dead time in the laboratory test was about 30 seconds. 109 Figure 43 compares the enantiomeric separation of DL-serine between the ETU test and a laboratory test with a similar GC column temperature program. For the ETU test, the GC column was held isothermally at 40˚C for about 3 minutes and ramped at about 9˚C•min -1 to 180˚C. For the laboratory tests, the GC column was held at 35˚C for 7 min and then ramped at 10˚C•min -1 to 182˚C. This 4 to 5-minute difference in the initial isothermal hold in ETU runs compared with laboratory tests is reflected in the roughly 4 to 5-minute difference in retention times of serine between the laboratory and ETU tests (Table 14).

Although the retention time of decanoic acid, methyl ester in the laboratory and the ETU cannot be directly compared due to differences in the initial isothermal hold at the beginning of the GC run, the ~4 to 5-minute difference is consistent with the 5-minute extra isothermal hold at the beginning of the run in the case of the laboratory, keeping in mind a slightly different start temperature (40˚C ETU, 35˚C lab). For low volatility molecules such as decanoic acid (C10), the isothermal hold in GC column temperature at 35-40˚C is sufficiently low that the compound is effectively immobilized during this low temperature isothermal hold time, prolonging its retention time in direct correlation with the hold time. The retention times of a given compound across the ETU tests are consistent with one exception. In the offline derivatization test of DL-serine, decanoic acid, and hexadecanoic acid (TID 8422), there is a broad peak at ions associated with alkane fragments (m/z 74, 87) appearing before a sharp peak of decanoic acid which is shifted much later in the run than in other tests. This alkane could also be a sign of decarboxylation of decanoic acid during the experiment. This test and potential explanations are discussed in Chapter V, Section V.4.2.2. This kind of retention time comparison described in this section validates the value of a retention time library from laboratory tests for aiding compound identification on MOMA flight-like data sets. Although simple mixtures of chemical standards, as presented here, can often be identified confidently by mass spectrum alone, this is not the case for more complex

III.3.4.3 Comparison of peak behavior between laboratory COTS GC-MS and MOMA ETU

The laboratory tests described in Sections III.3.1, III.3.2, and III.3.3 utilized injection by handheld syringe to a COTS GC-MS whereas MOMA ETU and FM tests utilize adsorption/thermal desorption traps for injection of compounds to the GC column. As discussed in Section III.3.4.1, the MOMA injection trap is heated from the trapping temperature to the maximum trap temperature in a given amount of time. In addition to an ambiguity in the exact injection time of a given compound, this slower injection technique can also result in broad, fronting, tailing, or possibly double peaks (Chapter V, Sections V.4.2) rather than the ideal Gaussian peak shape.

Figure 44 shows a comparison of peak shape for both 3-methylhexane and for the separated enantiomers of L-D-serine. For the ETU test, the GC column was held isothermally at 37˚C. For the laboratory test, the GC column was held at 35˚C for 7 min and then ramped to 182˚C at a ramp rate of 10˚C•min -1 . In this case, the time at the maximum trap temperature was taken as t0.

3-methylhexane, laboratory

Enantiomeric separation of 3-methylhexane was not observed, which is expected based on the given run conditions and on previous laboratory tests performed also on a Chirasil Dex column [START_REF] Freissinet | Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases[END_REF]). In the ETU tests, the peak width at half height of the 3-methylhexane peak (m/z 43) was 0.17 min, while in the laboratory tests, the peak width was 0.05 min (Figure 44). Likewise, the enantiomeric peaks of L-D-serine (m/z 70) are broader in the ETU tests, about 0.14-0.20 min (ETU) compared with 0.028 min (laboratory). As defined in Equation 4, the time separating the two enantiomeric peaks is also important for calculating enantiomeric resolution. Differences in this value between the ETU and laboratory may be explained by a difference in the method for controlling the flow rate as well as some ambiguity in selecting the peak center due to the asymmetric peak shape in the ETU case. A more efficient (sharper), symmetric peak in the laboratory results is consistent with the fast injection allowed by a syringe injection, the most efficient injection method for the given gas chromatography laboratory setup. The broader, slightly-tailing peaks in the ETU results are consistent with injection by adsorption/thermal desorption traps, in which the injection is less rapid and can be considered as a worst case. Since 3-methylhexane is a chiral molecule, the observed peak widening can also be explained by a coelution of both enantiomers. The difference between enantiomeric separation performed on a laboratory instrument versus in a MOMA ETU setting illustrates the challenge of resolving enantiomers on Mars. However, a column's ability to resolve enantiomers is determined by its ability to separate enantiomeric peaks to half height. Although the implementation of enantiomeric separation for MOMA will undergo additional optimization on ETU and laboratory models before MOMA lands on Mars, these initial ETU tests show a successful separation of the enantiomers of an amino acid. Enantiomeric separation of chiral molecules and enantiomeric excess in ETU tests is further discussed in Section III. 3.4.4. A discussion of peak behavior in laboratory and ETU setups with more complex gas processing systems and adsorption/thermal desorption trapping is in Chapter V, Section V.4.2.

III.3.4.4 Racemization and enantiomeric excess

Racemization could be induced during both the heating of instrument elements (e.g., ITs) or during the derivatization reaction [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]. Multiple chiral molecules were run on the ETU during the 2018 coupling campaign, including 2-butanol, 2-pentanol, 2-hexanol, 3-methylhexane, and DL-serine. Quantification of chiral resolution or enantiomeric excess are not given for the chiral alcohols due to saturation of the column and ion trap during these injection runs, which were induced by high injection volumes. However, multiple blank tests were run after the injection of the chiral alcohol mixture (TID 8413) in which sharp peaks and enantiomeric separation (of 2pentanol and 2-butanol) of the injected alcohols were observed (e.g., top panel of Figure 41). The 2-hexanol chemical standard used in the ETU tests was in its L-enantiomeric form only, which explains why it does not show clear enantiomeric separation like 2-butanol and 2-pentanol (Figure 41). However, multiple peaks of each alcohol are observed in these subsequent blank runs, likely due to a saturation of the GC column based on the quantity of standard injected, including a double peak of 2-hexanol (Chapter V, Section V.4.2). Due to the double peaks, including shoulder peaks on each of the 2-hexanol double peaks, it is not confirmed that racemization through thermal desorption did not occur for 2-hexanol by these tests.

Offline and online DMF-DMA derivatization of DL-serine was performed during the ETU tests and the D-and L-enantiomers of serine were successfully separated to baseline across these tests.

In addition to experiencing racemization during the derivatization process, amino acids may experience racemization during the flash heating of the traps during injection. Only the D-form of serine was introduced to the system in two tests (TID 8428 and TID 8429, an online derivatization run and an offline derivatization run, respectively). The racemization rate cannot be calculated from the given data since there was a known background of L-Serine in the instrument prior to the introduction of only the D-form of Serine and it is unclear if L-Serine is detected from the introduction of L-Serine to the oven in the first online derivatization test, since the signal does not significantly increase. Although the enantiomeric excess is low in the test in which only D-Serine is introduced in the oven (5.0% ee of D-Serine), the L-Serine signal remains around the same levels as in the previous test (with a slight increase). It is recommended that a cleaner test be conducted in the next GC-MS coupling campaign in order to quantify the difference in derivatization efficiency of chemical standards during offline and online derivatization and to evaluate racemization rates of due to MOMA-like system components.

Enantiomeric resolution is calculated for each of the enantiomeric separations of L-D-serine listed in Table 15 (Equation 4). The values for enantiomeric resolution on the ETU (on the order of RS = 1 to RS = 4 in the ETU tests) are lower than that of enantiomeric separation of DL-serine on a laboratory COTS GC-MS on the MOMA flight spare GC chiral column (on the order of RS = 8 to RS = 9 in laboratory tests of chemical standards), which is expected due to the less performant injection method of the ETU. The enantiomers of serine are separated to baseline (separation at or below half-height-half-width of the chromatographic enantiomeric peak) using a 10˚C•min -1 column temperature ramp. It has been demonstrated that lower flow rates can improve enantiomeric resolution (Section III. 3.3). A more efficient (sharper), symmetric peak in the laboratory results is consistent with the fast injection allowed by a syringe injection, the most efficient injection method for our given gas chromatography setup. The broader, slightly-tailing peaks in the ETU results are consistent with injection by adsorption/thermal desorption traps, in which the injection is less controlled and can be considered as a worst case. The difference between enantiomeric separation performed on a laboratory instrument versus in a MOMA ETU setting illustrates the challenge of resolving enantiomers on Mars. Although the implementation of enantiomeric separation for MOMA will undergo additional optimization on ETU and laboratory models before MOMA lands on Mars, these initial ETU tests show a successful baseline separation of the enantiomers of an amino acid.

As discussed in Chapter I (Section I.1.2.2.1 and Section I.3.2.3) amino acid enantiomeric excess is a detectable bioindicator enabled by the enantioselective column on MOMA. Even though amino acid homochirality can serve as an important biosignature, recent measurements of lenantiomeric excess values for some conglomerate-forming a-H proteinogenic amino acids on fragments of the Tagish Lake meteorite [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF] show that nonbiological processes could also lead to significant enantioenrichment for some amino acids. Additionally, a full study of the potential for racemization of chiral mixtures within instrument elements (e.g., the heating protocol of the hydrocarbon traps) is required to rule out any important instrument influence on amino acid enantiomeric excess results. Both of these examples emphasize the need for multiple chemical channels of observations in order to establish confidence values for the biotic or abiotic nature of collected martian samples [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF].

III.4 Conclusions

The MOMA FM is finalized and integrated in the rover, and the range of operating conditions of the instrument under the Mars surface environmental conditions has been constrained (e.g., carrier gas flow rates, transfer line temperatures). This chapter presents the chromatographic column package selected for MOMA, along with the analytical procedures that will be used on Mars, a retention time and mass spectral library to support the analyses of eventual Mars flight data, and a demonstration of the analytical performance of a laboratory system that simulates the flight experiment and the in situ operating conditions. The laboratory data is also compared to data from a MOMA ETU coupling campaign that took place in 2018. The conclusions and recommendations coming out of this study are detailed in the following summary of this chapter's results.

The following main conclusions and results which correspond to sections of this chapter are given below.

III.a.

Column efficiency in laboratory tests (Section III.3.1) i.

Minimum HETP values were achieved at linear carrier gas velocities of 60 cm•s - 1 (Q BOND), 46-49 cm•s -1 (MXT CLP), 48-53 cm•s -1 (MXT 5), and 55-67 cm•s -1 (Chirasil Dex) for each GC column with selected compounds and isothermal hold temperatures. ii.

The Chirasil Dex column displays the greatest variation in minimum HETP value with column temperature: 61-67 cm•s -1 (60˚C) and 55-61 cm•s -1 (115/120˚C). iii.

Linear gas velocity values (III.a.i.) are consistent with the adjustability of MOMA's flow rate, 0.8-1.4 mL•min -1 .

III.b.

Separation power in laboratory tests (Section III.3.2) i.

A retention time library of III.b.i. is proposed as a tool for interpretation of ETU and flight data (Table 12 andTable 13). ii.

The column instrument package separates and detects a wide range of organic and inorganic volatile compounds, from noble gases to hydrocarbon chains with up to 29 carbon atoms (C29). iii.

The four MOMA GC columns have a combined effectiveness to efficiently separate compounds targeted by MOMA within constrained parameters such as run time (Figure 37). iv.

The MOMA GC column package has the capability to enable detection of multiple parameters indicative of terrestrial biology. (Section I.1.2.2, III.3.2.4). v. The MOMA GC package will improve upon the SAM GC package by enabling detection of higher molecule weight molecules under its nominal operations.

III.c.

Enantiomeric separation in laboratory tests (Section III.3.3) i. "Mid-" (55-60 cm•s -1 ) to "low-" (35-55 cm•s -1 ) range helium velocities enable better enantiomeric resolution. ii. Demonstration of additional separation of enantiomeric species using a lower temperature ramp and flow rate. Enantiomeric separation was not observed for all of the chiral amino acids that were tested even when a lower temperature ramp and flow rate were employed (enantiomeric separation was not observed for 2 out of 5 chiral amino acids under these modified conditions), showing that the MOMA GC package will not achieve this measurement for all chiral molecules under its expected operational conditions. iii. Detection of amino acid enantiomers in the presence of a natural sample demonstrates the utility of III.b.i.

III.d.

Comparison of laboratory and ETU tests (Section III.3.4) i.

Demonstration of identification confirmation of 3-methylhexane, L-D-serine, and decanoic acid, methyl ester on the MOMA ETU by laboratory retention time. ii.

Demonstration of more performant separation of compounds and of the enantiomers of L-D-serine in the laboratory versus in an ETU experiment. iii.

Conduct a cleaner test in the next GC-MS coupling campaign in order to quantify the difference in derivatization efficiency of chemical standards during offline and online derivatization.

The following future studies and recommendations are proposed.

III.R.a. Systematic testing of the desorption efficiency of different classes of molecules across a range of molecular weight with the MOMA IT traps.

III.R.b.

Systematic testing of the racemization rates of chiral molecules induced by the heating profile of the MOMA IT traps.

Additional discussion on the characterization of GC systems prior to launch

As MOMA prepares for the launch and landing of the Rosalind Franklin rover, the work performed in this present study evaluates the performance of the four different gas chromatographic capillary columns coming from the same batch as those integrated in the FM. This work establishes a database of the retention times and mass spectra of the most probable organic compounds on Mars based on influx from the interplanetary medium, potential hydrothermal systems, atmospheric synthesis, and/or biological origins. This database is a necessary tool in order to robustly make identifications of target compounds within flight data. This symbiotic relationship between laboratory and flight data for enabling the strict identifications of target species has been previously demonstrated through the detection and identification of compounds using the SAM instrument and associated laboratory experiments (Eigenbrode et al. 2018;[START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Szopa | First Detections of Dichlorobenzene Isomers and Trichloromethylpropane from Organic Matter Indigenous to Mars Mudstone in Gale Crater, Mars: Results from the Sample Analysis at Mars Instrument Onboard the Curiosity Rover[END_REF].

Following the finalization and delivery of the MOMA flight model, this study helps to redefine the constraints of the space instrument, since it is understood that space instrumentation is far less performant than traditional laboratory instrumentation and protocol. For example, this work demonstrates the more performant separation of the enantiomers of L-D-serine in the laboratory versus in an ETU setting due to a more efficient injection by syringe (laboratory) rather than by adsorption/thermal desorption traps (space experiment). However, this study also serves to propose protocol which can improve the separation of compounds and the likelihood of a strict identification. For example, in the case of the separation of the enantiomers of amino acids, lower temperature ramp and flow rates are required. Since these conditions require more energy resources from the spacecraft, plans for decision trees during Mars operations will need to consider these requirements in order to meet science objectives.

In addition to the difference in performance between the flight experiment and the laboratory, the number of peaks and the level of complexity of a chromatogram obtained from the pyrolysis and/or derivatization of a martian sample, which includes the presence of a mineral matrix, is significantly greater than those obtained through the injection of chemical standards. A natural sample spiked with amino acids was tested in order to observe the effect of the presence of a mineral phase on the complexity of the chromatogram and the ability to resolve specific enantiomers in a scenario with more realistic background. The coupling of the chromatographic system with preparative wet chemistry in the form of MTBSTFA and DMF-DMA derivatization enables the detection and identification of additional species of specific astrobiological interest such as amino acids and carboxylic acids, but also complicates gas chromatograms with additional byproduct peaks coming from the derivatization reagent. Therefore, the database built for this study also presents the mass spectra and relative retention times that can be expected from targeted molecules in order to make better identifications of martian organic compounds.

This study shows that the gas chromatographic system of the MOMA experiment is an efficient tool for characterizing complex volatile materials. Its design enables separation and identification of a range of organic species and some inorganic species that could be expected to be present in martian surface and subsurface samples, including a range of alkanes, alcohols, carboxylic acids, as well as amino acids and their enantiomers. MOMA can expect to detect up to an alkane with 29 carbon atoms using the general purpose (WCOT) columns (MXT 5 and MXT CLP) and up to an alkane with 21 carbon atoms with the chiral column due to its lower maximum temperature of use. Due to the nominal run conditions of the GC system (Table 8), which are constrained by the space experiment, MOMA cannot expect to detect all potential compounds of interest. For example, molecules such as mellitic acid, which have up to six derivatization sites, are not detectable after either MTBSTFA or DMF-DMA derivatization due to the final molecular weight of the derivatized molecule. The way in which the molecule is altered by derivatization and therefore its characteristics which determine its retention time on the column (e.g., boiling point, molecular weight) coupled to the characteristics of a given column (e.g., the polarity of the stationary phase, the maximum temperature of use of the column) determine if the molecule is detectable within a nominal MOMA run. The ability of the MOMA gas chromatographic column package to test multiple parameters (e.g., relative abundance of amino acids, enantiomeric excess, patterns in lipid hydrocarbons, chain length distributions as a function of carbon number) enables a confidence value to any potential biosignature detection [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF].

The MOMA FM recently underwent thermal vacuum testing at TAS-I. Additionally, development of the MOMA testbed is underway at the GSFC and follow-up tests on engineering test units for both the GC, MS, and further coupling campaigns are planned. Although the launch schedule has been recently updated, the plan continues for the ExoMars rover to travel to Mars, with an updated launch date currently projected to be between August and October of 2022. Tests that have been and will be performed on the MOMA FM, testbed, and ETU will allow the refinement of our understanding of the GC-MS instrument capabilities. Further iterations on these types of laboratory studies will enable strict identifications of targeted molecules of astrobiological interest once on Mars.

Chapter IV: Gas chromatography-mass spectrometry analysis of organic molecules adsorbed on montmorillonite in the context of ExoMars's MOMA experiment Abstract MOMA is an instrument onboard the Rosalind Franklin rover that is scheduled to be launched to Mars in the summer of 2022 as part of the ExoMars mission. This experiment includes a GC-MS instrument dedicated to the in situ analysis of organic molecules present in martian samples collected by the rover at the surface down to 2 m depth. Many studies have explored the capabilities of the GC-MS analytical and wet chemistry protocols using chemical standards, but it is yet to be fully explored how the solid mineral matrix of samples may impact the analysis. The presence of salts and a mineral matrix have been shown to deactivate or reduce the derivatization reaction efficiency. The presence of perchlorate on Mars can also cause potential problems for detection of organics by GC-MS. This study tests the capabilities of pyrolysis-, derivatization-, and thermochemolysis-GC-MS analysis to detect four organic compounds, adenosine 5'monophosphate (AMP), L-glutamic acid (Glu), L-phenylalanine (Phe), and phthalic acid (PhA), which have been adsorbed on to a mineral, montmorillonite. Montmorillonite is used in this study since phyllosilicates are potentially present at Oxia Planum, the selected landing site of ExoMars. Tests were performed on samples containing organic molecules at different concentrations (5, 1, 0.1 wt. %), and with or without the addition of magnesium perchlorate. This study shows that the MOMA GC-MS package enables detection of each target organic molecule or its products in the presence of a phyllosilicate across multiple GC-MS sub-modes. While chlorinated hydrocarbons are produced during the higher temperature sample treatments (pyrolysis and thermochemolysis), detection of target organics are not hindered at the given concentrations. This study demonstrates that (i) the derivatization reaction is preserved in the presence of salts and in the presence of the montmorillonite mineral, (ii) the presence of the mineral matrix likely does influence the number and types of organic products based on catalytic or preservative effects and based on the specific adsorption efficiency and location of organics to the mineral, and (iii) the MOMA wet chemistry package is effective for targeting a range of organic compounds. These results will be important analog GC runs during MOMA operations on Mars in order to predict and identify compounds of interest, including degradation and reaction products, in flight chromatograms, as well as to indicate the potential martian parent mineral.

IV.1. Introduction

As introduced in Chapter I, the MOMA experiment will travel to Mars onboard the rover of the joint ESA/Roscosmos ExoMars 2022 mission. MOMA is a miniaturized chemical laboratory specifically dedicated to analyzing the organic and inorganic content of samples collected by the rover at the martian surface and subsurface down to 2 meters deep [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]). MOMA will go a step beyond characterizing habitability of Mars and will search for traces of life, or biomarkers, including nucleobases and amino acids, fundamental building blocks of terrestrial life [START_REF] Vago | Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover[END_REF]). The MOMA GC-MS will respectively separate the volatile compounds produced from heating (pyrolysis) or chemical treatment (derivatization, thermochemolysis) of the samples, and provide a spectral signature of each compound. In order to widen the detection capabilities for compounds of astrobiological interest using GC-MS, MOMA carries onboard wet chemistry, used to produce controlled reactions to protect reactive groups of polar molecules. MOMA carries three chemical reagents, N, N-Dimethylformamide dimethyl acetal (DMF-DMA) and N-methyl-N-tert-butyl-dimethylsilyltrifluoroacetamide (MTBSTFA) for derivatization and tetramethylammonium hydroxide (TMAH) for thermochemolysis, each one with the capability to reveal specific properties of organic molecules.

Chapter III explores MOMA's ability to separate organic compounds using its GC package. These tests were conducted using chemical standards since the study was focused on the retention time of target molecules on the MOMA FS column and the mass spectrum of a given compound's derivatives. This chapter will continue to assess the capabilities of the GC-MS technique for its applicability to the search for organic molecules on the martian surface with added complexity to the sample under testing. As introduced in Chapter III, Section III.3.3.2, studies with chemical standards do not consider the influence of a mineral matrix on the analysis. The presence of a mineral matrix can have an effect on the products produced in pyrolysis, derivatization, and thermochemolysis studies. For example, montmorillonite has been shown both to be capable of stabilizing an organic acid by adsorption or to act as a catalyst in promoting the degradation of the organic acid [START_REF] Hedges | The effect of various clay minerals on the thermal decomposition of stearic acid under 'bulk Flow' conditions[END_REF]. The presence of a mineral matrix has also been shown to interfere with the derivatization reaction by deactivation of the reagent or by preferential derivatization with water or salts [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF][START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF].

Montmorillonite is a layered silicate or clay mineral of the smectite family possessing structural characteristics comprised of stacks of hydrated aluminosilicate [START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF]. The crystal structure of layered silicates is characterized by two-dimensional layers formed by an octahedral sheet of alumina or magnesia between fused silica tetrahedral sheets [START_REF] Brindley | Crystal Structures of Clay Minerals and their X-Ray Identification London[END_REF]). Stacking of these layers form van der Waals gaps or galleries (Figure 46), also known as interlayers. The interlayers are occupied by water and exchangeable cations, typically Na + and/or Ca 2+ , which balance the charge deficiency generated by isomorphous substitution within the layers [START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF]). Variation in the amount, type, and crystallographic origin of the excess layer charge determines the type of layered silicate, which encompasses naturally occurring layered silicates (including montmorillonite) and synthetic layered silicates (e.g., laponite). These different layered silicates exhibit different physical and chemical characteristics, such as layer size, stacking perfection, reactivity, and Lewis acidity [START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF], which can have an effect on the interactions between clay minerals and organic matter and informs the physical and chemical separation of organic matter from clay minerals [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF] as in sample handling and GC-MS analysis utilized with space experiments.

A range of tests utilizing chemical standards have been conducted in order to understand the GC-MS analysis and wet chemistry techniques which will be carried onboard MOMA, e.g., Buch et al. (2006); 2019) , but there is remaining work to understand the effect of the mineral matrix on the GC-MS analysis as well as to constrain expected chromatograms for target molecules. Phyllosilicate-bearing terrains are expected at Oxia Planum, the landing site for the Rosalind Franklin rover. A relevant Oxia Planum analog sample for laboratory testing still remains to be fully constrained [START_REF] Poulet | Modal Mineralogy of Phyllosilicate-and Carbonate-Bearing Terrains from Spectral Modeling[END_REF][START_REF] Quantin | Oxia Planum, The Landing Site for ExoMars[END_REF]) and additional minerals to those seen from orbit are likely to be detected in situ [START_REF] Rampe | Sand Mineralogy Within the Bagnold Dunes, Gale Crater, as Observed In Situ and From Orbit[END_REF]. Montmorillonite specifically has not yet been detected at Oxia Planum, to understand the multi-technique results. Part of such characterizations has been reported in [START_REF] Fornaro | UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples: the case of Phthalic Acid, Adenosine 5'-Monophosphate, L-Glutamic Acid and L-Phenylalanine Adsorbed onto the Clay Mineral Montmorillonite in the Presence of Magnesium Perchlorate[END_REF]. The analysis of the other data is in progress by MOMA and ExoMars teammates as of the publication date of this thesis. This thesis chapter will focus only on analysis of these samples by GC-MS.

This study tests the capabilities of the GC-MS technique to detect four molecules of exobiological interest, adenosine 5'-monophosphate (AMP), L-glutamic acid (Glu), L-phenylalanine (Phe), and phthalic acid (PhA), which have been adsorbed on montmorillonite, at three concentrations and with or without the addition of magnesium perchlorate. Amino acids and carboxylic acids are of particular interest for astrobiology [START_REF] Davila | Chance and necessity in biochemistry: implications for the search for extraterrestrial biomarkers in Earth-like environments[END_REF], require derivatization for optimal detection by GC-MS, and have been detected in meteorites and comets [START_REF] Altwegg | Prebiotic chemicals-amino acid and phosphorus-in the coma of comet 67P/Churyumov-Gerasimenko[END_REF][START_REF] Glavin | Amino acids in the Martian meteorite Nakhla[END_REF][START_REF] Glavin | Re-examination of amino acids in Antarctic micrometeorites[END_REF][START_REF] Sephton | Pyrolysis and mass spectrometry studies of meteoritic organic matter[END_REF]). The four molecules chosen for this study compose a complimentary test set for GC-MS analysis according to several criteria, including (1) the potential to elute across a range of retention times from the GC columns, e.g., molecular mass ranges from 147.1 g•mol -1 (Glu) to 347.2 g•mol -1 (AMP), (2) representatives of several physiochemical characteristics, e.g., aliphatic charged side chain (Glu) and a hydrophobic aromatic side chain (Phe), ( 3) potential presence in the samples that can be collected at Mars's surface and subsurface, i.e. the molecules selected are among the most abundant within known exogenous sources or correspond to evolution products of organic molecules under martian environmental conditions, e.g. carboxylic acids as products of oxidation [START_REF] Benner | The missing organic molecules on Mars[END_REF] and potential precursors to previously detected chlorinated hydrocarbons (Miller et al. 2016), i.e., phthalic acid as one of the candidates of the precursor to the chlorinated hydrocarbons detected by SAM, although benzoic acid is the current preferred precursor. The perchlorate anion (ClO4 -) was first detected in the martian regolith by the TEGA instrument onboard the Phoenix Lander at concentrations of 0.4 to 0.6 wt. % [START_REF] Hecht | Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site[END_REF]) and Mg 2+ , Na + , K + , and Ca 2+ cations were found to contribute to this signal at lower concentrations, informing the selection of magnesium perchlorate in some of these samples.

These samples are analyzed using all the sample preparation methods implemented in the MOMA experiment, i.e. flash and ramp pyrolysis-GC-MS, derivatization-GC-MS (MTBSTFA and DMF-DMA), and thermochemolysis-GC-MS (TMAH). This chapter will first cover a demonstration of the complementarity, wide-ranging capabilities, and limitations of the MOMA GC-MS analysis on a set of samples which are representative of one type of martian sample in terms of the type of mineral matrix and the types of molecules to be sought across a few molecular types and mass range. Next, this chapter will explore the effects of Mg-perchlorate on the GC-MS results.

Additionally, this study contributes to ExoMars-wide efforts to build combined operations plans through the testing of the same set of samples across instrument teams, but this is not covered directly in this chapter.

IV.2. Materials and methods

IV.2.1. Samples

Samples were prepared by Teresa Fornaro (Istituta Nazionale di Astrofisica (INAF); Florence, Italy) and the sample preparation is fully described in [START_REF] Fornaro | UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples: the case of Phthalic Acid, Adenosine 5'-Monophosphate, L-Glutamic Acid and L-Phenylalanine Adsorbed onto the Clay Mineral Montmorillonite in the Presence of Magnesium Perchlorate[END_REF]. The original mineral substrate was Ca-rich montmorillonite ("Cheto") from County of Apache, State of Arizona, USA, The two derivatization methods were performed on the samples using a MTBSTFA/DMF solution at a 3:1 ratio and DMF-DMA. The purities were ≥99.0% (MTBSTFA), >95% (DMF-DMA), and >99.9% (DMF) and all three chemicals were purchased from Sigma-Aldrich. For MTBSTFA derivatization, two techniques were explored for extraction of the organics from the mineral matrix: extraction by solvent and a direct derivatization. In the solvent extraction procedure, about 5 mg of sample was mixed with 15 µL of a water and isopropanol solution (1:1 by volume). The solution was shaken by hand for about 1 minute at room temperature. The solution was then left to evaporate under N2 flow for 30 min. Next, 4 µL of MTBSTFA/DMF (3:1) was added to the dried extract and underwent derivatization at 75˚C for 15 min. For direct derivatization, 15 μL of 1 or a 30 m Zebron ZB-5MSplus (30 m x 0.25 mm x 0.25 µm) for the tests on Batch 2. The GC column used for the thermochemolysis tests was a Supelco SLB-5MS (30 m x 0.25 mm x 0.25 µm). The MOMA MXT 5 column (Chapter III, Section III.2.2.1) has a stationary phase of the same composition as the stationary phase of all three columns used for the laboratory experiments.

Although different in length from the MOMA GC columns, which are 20 m long (Chapter III, Section III.2.2.1), all four columns (the three columns used in this laboratory study and the MOMA MXT 5 columns) have a stationary phase of the same composition (5% phenyl, 95% dimethylpolysiloxane). It is only the way in which the stationary phase is deposited on the capillary wall and the polymerization that can differ. However, since the geometry and stationary phases are the same, the columns have similar separation capabilities.

For the pyrolysis tests, the GC column was held at 40 C for either 1 or 7 min and then ramped up to 300 C at 10˚C•min -1 . For the derivatization tests, the GC column was held at 40˚C or 45 C for 1 min and then ramped up to 300 C at 10˚C•min -1 . The helium carrier gas flow rate was kept constant at 1.0 mL•min -1 or 1.1 mL•min -1 . The split ratio was 1/10 or 1/50. The injector temperature was 250˚C except when the D8-naphthalene internal standard was employed because of its high boiling point. Then the injector temperature was increased to 280˚C. For the thermochemolysis experiments, the GC column was held at 45˚C for 1 min and then ramped up to 300˚C at 10˚C•min - 1 . The injector was set at 280°C. The helium carrier gas flow rate was 1.1 mL•min -1 with a split ratio of 1/50. The mass range was m/z 21-535.

IV.2.2.3. Fidelity of laboratory setup to MOMA FM

The FM of MOMA is now finalized and integrated in the rover, and the range of operating conditions of the instrument under the Mars surface environmental conditions has been constrained (e.g., carrier gas flow rates, transfer line temperatures). These parameters have important differences from the laboratory experiments. Expected GC-MS operating conditions for Mars are shown in Table 18.

IV.3. Results and Discussion

IV.3.1. Pyrolysis studies

IV.3.1.1 Pyrograms

Products of the flash pyrolysis of Mont+AMP, Mont+Glu, Mont+Phe, and Mont+PhA samples were detected and compared with those produced using a MOMA-like ramp pyrolysis. PhA samples at 5 wt. % were run under flash and ramp pyrolysis and more reaction products were observed after flash pyrolysis (Section IV.3.1.2). The products of the ramp pyrolysis, which is more similar to the MOMA flight pyrolysis, are shown in Figure 52 and Figure 53. In order to have controlled blank tests, fused silica and montmorillonite blanks were run under the same pyrolysis conditions prior to testing of the doped samples. Figure 49 shows trace contamination in the montmorillonite blank, which is not present during the same experiment with clean fused silica. This indicates the contamination does not come from the instrumentation. This contamination could be from the plastic Eppendorf vials in which the samples were stored or contamination from the montmorillonite samples themselves which was not fully removed from the mineral during the cleaning process or was introduced during sample handling. After investigation with Teresa Fornaro, it was assumed that the contamination likely originated from the mortar and pestle used to crush the montmorillonite. High amounts of water are observed which is expected from clay samples. High amounts of CO2 are observed from the oxidation of organics in the presence of the oxygen from atmosphere.

Table 18: Technical parameters of GC-MS analysis in the FM and in the laboratory for this study. It is expected that the maximum temperature of the pyrolysis ovens will be 800 to 850˚C [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. *To be refined. The main products of glutamic acid in the pyrolysis study shown here include HCN, acetonitrile, propanenitrile, and pyrrole (Figure 52). Pyrrole is formed by a reaction of water elimination associated with CO2 elimination as proposed by [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF] and shown in the reaction diagram in Figure 50. Nitriles are formed following the decarboxylation of the amino acid, after which the amine eliminates hydrogen and forms a nitrile [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF]. Amines were not detected, but may be missed because the GC column in use is not intended for separation of low molecular weight molecules, and short amines may be hidden under the large peaks of poorly retained compounds, including the contamination from the montmorillonite.

Experimental

The pyrolysis of Phe surprisingly produces a large suite of mostly aromatics and N-containing aromatic compounds (Figure 53). One decomposition path for the pyrolysis of phenylalanine is a decarboxylation with a resulting amine formation. This is the formation pathway of pyrolysates such as phenethylamine (Peak 26 in Figure 53). Other compounds present at high levels in the pryolysate of phenylalanine are compounds such as toluene and bibenzyl. The proposed formation of these compounds is by an initial reaction that generates benzyl radicals as proposed by Moldoveanu (2010) (Figure 51). These benzyl radicals further react with the phenylalanine The major pyrolysis products of PhA include phthalic acid itself, phenol, benzoic acid, biphenyl, and benzophenone (Figure 53). Those are all aromatic compounds expected to derive from the decarboxylation, dimerization or rearrangements of phthalic acid. Decarboxylation processes have been shown to start at pyrolysis temperatures higher than 450˚C, with the formation of CO2, benzoic acid, and benzene [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF]. While benzene is also expected from the pyrolysis of phthalic acid adsorbed on a clay, the presence of benzene in the background (as seen in the montmorillonite blank) does not allow the deconvolution between the benzene present in the pure clay sample and the benzene coming from the decarboxylation of phthalic acid.

The comparative pyrolysis of only four potential compounds adsorbed on a clay shows a high variability in the number of pyrolysis products that are produced for each sample. For example, the Mont+AMP chromatogram is very simple: nitriles such as acetonitrile and HCN are observed from AMP degradation and CO2 from oxidation of AMP during a MOMA-like run time. However, the chromatogram for the pyrolysis of Mont+Phe is extremely complex, with over 30 aromatic and N-containing aromatic compounds identified from the degradation of Phe. It is possible that the high number of degradation or reaction products coming from the pyrolysis of Phe are due to that particular amino acid staying longer in the pyrolysis reaction zone. If so, secondary reaction processes, mainly radical reactions, would have more time to develop, causing this broader range of secondary products. This hypothesis is supported by the large number of products in the Phe pyrogram (Figure 53) attributed to formation by secondary reactions with benzyl radicals. The residence time of the molecule in the pyrolysis zone could be longer if phenylalanine interacts more strongly with the montmorillonite than the other test compounds. Indeed, NIR measurements conducted on these samples showed features indicating involvement of the C-H group of the aromatic ring in the interaction with the mineral as well as a band attributed to molecule-mineral interactions, indicative of chemisorption of the molecule to the mineral specifically for the samples doped with Phe [START_REF] Fornaro | UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples: the case of Phthalic Acid, Adenosine 5'-Monophosphate, L-Glutamic Acid and L-Phenylalanine Adsorbed onto the Clay Mineral Montmorillonite in the Presence of Magnesium Perchlorate[END_REF].

It is also possible that the formation of some of the observed products arise from catalytic effects from the presence of the mineral itself [START_REF] Mortland | Clay-Organic Complexes and Interactions[END_REF]), but pure organics were not tested under the same pyrolysis conditions. The catalytic functions of clay minerals for natural hydrocarbon generation have been demonstrated [START_REF] Hedges | The effect of various clay minerals on the thermal decomposition of stearic acid under 'bulk Flow' conditions[END_REF][START_REF] Jurg | Petroleum Hydrocarbons: Generation from Fatty Acid[END_REF], with the clay minerals of the smectite group, such as montmorillonite, receiving particular attention for known catalytic activities [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF]. Montmorillonite has been shown to be capable of stabilizing an organic acid by adsorption or act as a catalyst promoting the degradation of the organic acid [START_REF] Hedges | The effect of various clay minerals on the thermal decomposition of stearic acid under 'bulk Flow' conditions[END_REF]. The presence of the montmorillonite mineral has also been shown to change the products of pyrolysis of organic compounds, through promotion of decarboxylation and Hoffman elimination of the organic [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF]. Pyrolysis of the pure organic compounds was not performed in this study shown here, and therefore this hypothesis cannot be confirmed by this test set. These two conditions (i.e., a longer residence time of the parent molecule in the pyrolysis zone and a catalytic effect by the mineral) are not mutually exclusive and both likely play a role in the pyrolysis products. The structural source of the adsorption of the organic compound to the mineral (i.e., interlayer or external) as well as the type of interlayer site (i.e., Brønsted acid sites or Lewis acid sites) influences the pyrolysis reaction pathway and reaction intensity of organic matter, with the interlayer spaces possibly being more important than external surfaces of montmorillonite for promoting or delaying the pyrolysis of organic matter due to the abundance of interlayer solid acid sites and the negative charge and steric hindrance of clay layers [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF]. For example, Lewis acid sites of montmorillonite were found to be responsible for the decarboxylation of organics, while Brønsted acid sites of montmorillonite were found to be capable of promoting the pyrolysis of nitrogen-containing organics through Hoffman elimination [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF]. Therefore, pyrolysate identifications presented in this section could be used to corroborate evidence of the adsorption of organic compounds on interlayer sites (e.g., Phe) in the multitechnique analysis of these samples (e.g., [START_REF] Fornaro | UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples: the case of Phthalic Acid, Adenosine 5'-Monophosphate, L-Glutamic Acid and L-Phenylalanine Adsorbed onto the Clay Mineral Montmorillonite in the Presence of Magnesium Perchlorate[END_REF].

Pyrolysis-GC-MS does not enable the direct detection of the starting organic compounds themselves in most cases (apart from phthalic acid) since (a) high heating of the sample causes fragmentation of individual molecules and (b) the level of volatility (low), reactivity (high), and thermal stability (low) of some molecules will not enable their detection by pyrolysis-GC-MS without the implementation of derivatization. However, it is possible to identify the starting organic molecule from its pyrolysates through such experimental laboratory work combined with an investigation of the pyrolysate formation mechanisms. However, the high number of potential pyrolysates of a single organic molecule in the presence of the montmorillonite mineral (i.e., Phe) demonstrates the potential complexity of deconvoluting pyrolysates of even more complex natural samples containing multiple organic species. In this scenario, the ability to confidently trace pyrolysates back to parent molecules may be unlikely. Multi-technique or multi-mode systems can aid in deconvoluting this complexity.

As missions such as ExoMars 2022 prepare for the analysis of flight data and continue the analysis of ETU data (Chapter III), it is important to build libraries of expected pyrolysis products of samples which are representative analog samples. Although these doped samples lack the complexity of natural Mars analog samples, they can be used to indicate the expected pyrolysis products of organic compounds of astrobiological interest in the presence of clay samples which can be expected on Mars. Chromatograms such as the ones in Figure 52 and Figure 53 will drive targeted searches for compounds in the more complex ETU and FM data.

IV.3.1.2 Flash pyrolysis vs. ramp pyrolysis

In addition to the presence of the mineral and the placement of the organic compound in relation to the surfaces and interlayers of the mineral matrix, the pyrolysis protocol itself, e.g., the amount of time in which the sample is in the pyrolysis reaction zone, and to what temperatures they are submitted, informs the type and number of pyrolysates. Figure 54 shows the pyrogram for MontP+PhA samples at 5 wt. % and compares the type and variety of pyrolysates between flash pyrolysis and ramp pyrolysis. Although these samples are from the batch doped with Mgperchlorate, the results of samples with Mg-perchlorate will be fully discussed in Section IV.3.4. The ramp pyrolysis is similar to the pyrolysis which will be performed on MOMA (Table 18).

A slightly larger variety of products is produced in flash pyrolysis compared to ramped pyrolysis, although the difference in the procedure account for the apparent difference and for the peak shape difference. Chlorobenzene is present in both pyrolysis modes, with peak areas that are similar. There are also a few chlorinated organics that are present in the flash pyrolysis chromatogram and not in the ramp pyrolysis chromatogram including chlorinated phenol, dechlorinated phenol, and trichlorinated phenol. PhA is the compound leading to the most differences between flash and ramp pyrolysis and this result is consistent with other studies [START_REF] Millan | Influence of Calcium Perchlorate on Organics Under SAM-Like Pyrolysis Conditions: Constraints on the Nature of Martian Organics[END_REF]. For Glu, Phe and AMP, the qualitative and quantitative results are comparable between the two pyrolysis techniques (flash and ramp). This is explained by the fast MOMA pyrolysis ramp (200°C•min -1 ) which approach the kinetics of a flash pyrolysis. Although not part of this work, it is interesting to note that a slower, SAM-like, pyrolysis ramp (35°C•min -1 ) leads to major differences with flash pyrolysis [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF].

Figure 54: Chromatograms obtained using flash and ramp pyrolysis. Flash (top) versus ramp (bottom) pyrolysis of MontP+PhA, 5%. 5.8 mg of sample were pyrolyzed in the flash pyrolysis and 3.2 mg of sample were pyrolyzed in the ramp pyrolysis. ( 1) benzene, (2) toluene, (3) chlorobenzene, (4) phenylethyne, (5) styrene, (6) phenol, (7) phenol, 2chloro-, (8) benzofuran, (9) 3-methylphenylacettylene or indene, (10) phenol, dichloro, (11) naphthalene, ( 12) benzoic acid, (13) naphthalene, methyl, ( 14) phthalic acid, ( 15) phenol, trichloro-, ( 16) biphenyl, (17) biphenylene, ( 18) biphenyl, chloro-, ( 19) dibenzofuran, (20) fluorene, (21) benzophenone, ( 22) benzoic acid, phenyl ester, (23) 9Hfluoren-9-one, (24) anthracene, (25) 9H-fluorene, 9-methylene-, ( 26) anthracene, 9-ethenyl-, ( 27) terphenyl, (28) anthracene, 9-methyl, ( 29) 9,10-anthracenedione. GC column: 40˚C (hold for 1 or 7 minutes), ramp to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 . The difference in initial isothermal hold time of the GC column is reflected in the retention time shifting.

IV.3.2. Wet chemistry

This section covers the derivatization (MTBSTFA/DMF, DMF-DMA) and thermochemolysis (TMAH) results on the samples. First, the blank tests of each wet chemistry protocol are presented and discussed (Section IV. In summary, MTBSTFA derivatives of Glu, Phe, and PhA were clearly detected at all three concentrations, while evidence of AMP was not detected at any concentration with MTBSTFA or DMF-DMA. Glu, Phe, and PhA at the highest concentration, 5 wt. %, were harder to detect with DMF-DMA derivatization as the chromatographic response was close to the noise limit. This difficulty prompted some optimization of the derivatization temperature protocol for DMF-DMA. DMF-DMA derivatives of Glu, Phe, and PhA were detected. TMAH thermochemolysis enables detection of methylated products of all four organic compounds as well as additional thermolysates.

IV.3.2.1. Wet chemistry blank tests

Blanks include not only instrumental blanks but also derivatization reagent blanks and derivatization reagent blanks with the montmorillonite mineral (Figure 55). Derivatization blanks are more complex than pyrolysis blanks because the heating of the derivatization reagent produces its own byproducts which can vary based on the temperature and duration of the derivatization reaction. This phenomenon is illustrated for DMF-DMA derivatization, which was performed at three derivatization temperatures (140˚C, 200˚C, and 250˚C). As the derivatization temperature increases, the number of DMF-DMA derivatization byproducts increases as well (bottom panel of Figure 55) which can interfere with the clear detection of targeted molecules. This relationship can pose a challenge for the detection of trace levels of volatile organics, since an increase in derivatization temperature can result in a higher derivatization yield of target compounds. This temperature relationship for the DMF-DMA derivatization of the samples is further discussed in Section IV.3.2.3.2.

There are not additional peaks produced from MTBSTFA derivatization at 250˚C in the presence of montmorillonite with the exception of a peak at about 19 minutes which is identified by NIST as phosphoric acid, 3tBDMS, but is likely not this molecule due to an unexpectedly short retention time for its given structure and molecular weight.

The derivatization temperatures (≤250˚C) are too low to see breakdown of the montmorillonite mineral, but the heating of clay samples shows a ready release of water. Decomposition of pristine montmorillonite has generally shown two regions occurring below 1000˚C. First, dehydroxylation of the aluminosilicate lattice has been shown to occur in temperature ranges between 500 and 1000˚C for pristine montmorillonite in conjunction with an initial transformation of the crystal structure into spinel, mullite, and/or pyroxenes (enstatite) [START_REF] Grim | Clay Mineralogy[END_REF][START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF]. Decomposition of pristine montmorillonite has also shown that free (adsorbed) water present between the montmorillonite crystallites and interlayer water residing between the aluminosilicate layers and comprising the hydration spheres of the cations will evolve between 100 and 400˚C [START_REF] Mackenzie | The Thermal Characteristics of Soil Minerals and the Use of These Characteristics in the Qualitative and Quantitative Determination of Clay Minerals in Soils[END_REF]. This second temperature regime is pertinent to our derivatization studies. Indeed, there are higher levels of tert-Butyldimethylsilanol (monosilylated water) and disiloxane, 1,3-bis(1,1-dimethylethyl)-1,1,3,3-tetramethyl-(bisilylated water) in the derivatization blank in the presence of montmorillonite (top panel of Figure 55) due to this release of water from the clay mineral which is then derivatized. This increase in the amount of derivatizated water is the main distinctive feature of the chromatogram between the derivatization blank and the derivatization blank in the presence of montmorillonite, which is consistent with the literature on the decomposition of montmorillonite in relation to temperature regimes.

The thermal decomposition of TMAH at 600˚C is well characterized [START_REF] He | Application of TMAH thermochemolysis to the detection of nucleobases: Application to the MOMA and SAM space experiment[END_REF]. About 65% of the distribution of thermolysis products of TMAH flash pyrolysis is composed of CO2 and trimethylamine (TMA). The chromatograms of the thermochemolysis blank and the thermochemolysis blank in the presence of the montmorillonite mineral are qualitatively similar (Figure 56). Therefore, even at the higher temperatures of the thermochemolysis reaction (600˚C; albeit for the shorter reaction time of 30 s) there is not evidence of the breakdown of the mineral in the GC chromatogram. However, since transformation of the crystal structure of montmorillonite has been observed between 500 and 1000˚C [START_REF] Grim | Clay Mineralogy[END_REF][START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF], it could be interesting to perform XRD and/or XRF analysis of the samples post-thermochemolysis to see if there are differences in the mineral phases or mineral chemical composition of the samples. The chromatogram (Figure 56) also illustrates how TMAH is not sensitive to water in contrast to the derivatization reagents such as MTBSTFA (top panel of Figure 55), since there are not the high levels of chemically functionalized water peaks that are visible in the derivatization blanks of MTBSTFA in the presence of montmorillonite.

IV.3.2.2. MTBSTFA derivatization

This section will discuss the solvent extraction and direct derivatization tests (Section IV.3.2.2.1), MTBSTFA derivatization products that were detected (Section IV.3.2.2.2) and the chromatographic response of these products across samples of different concentrations of the organic compound (i.e., 5, 1, 0.1 wt. %) (Section IV. 3.2.2.3). In our total experimental test set, three test repetitions at all three concentrations for each organic compound were only performed for MTBSTFA derivatization using direct derivatization.

IV.3.2.2.1. Solvent extraction vs. direct derivatization

The extraction techniques traditionally used in a laboratory are not the same for planetary operations due to efforts to miniaturize, constrain mass, and reduce complexity in the space experiment. Additionally, there can be slight or substantial differences between protocols, instrumentation, and settings of laboratory experiments versus more flight-like models. Therefore, it is important to test in the laboratory which differences can arise in the results from these types of technical and instrumental nuances. Solvent extraction was used to test the chromatographic response of organic compounds. Solvent extraction followed by MTBSTFA derivatization (top graphic in Figure 48) was first implemented on the montmorillonite samples in order to gauge the chromatographic response following an efficient extraction. This extraction procedure yielded a saturation of the chromatographic column, which is evidenced by the high chromatographic response values shown in Figure 57. Therefore, solvent extraction served as a litmus test for proceeding to direct derivatization, for which the extraction efficiency is not well characterized. The GC-MS capability based on SAM and MOMA aims to conduct a sensitive and broad survey of trace organic species contained in solid-phase martian samples. The in situ wet chemistry capability on these experiments is composed of a chemical derivatization of extracted organics to produce volatile species followed by GC-MS analysis. For MOMA, it is possible to preheat the sample prior to MTBSTFA or DMF-DMA derivatization in order to opportunistically aid in the extraction of organics from the mineral matrix via thermal desorption. Here the difference in extraction efficiencies between solvent extraction (a more traditional laboratory extraction technique) and direct derivatization which aims to more closely mimic the space experiment are briefly discussed. The extraction of organic matter from solid samples in laboratory testing will be discussed further in Chapter V.

It has been shown that amino acids have a better yield of recovery if chemical extraction from the solid mineral matrix is applied prior to pyrolysis in order to avoid decomposition (Glavin & Bada 1998). Past studies have developed solvent extraction techniques for laboratory extraction of amino acids and carboxylic acids from martian analog samples and meteorites in order to minimize the power consumption and large solvent volume needed for the more classical Soxhlet extraction and to maximize yields of these target molecules [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. Figure 48 shows the difference in chromatographic response between Mont+Glu, Mont+Phe, and Mont+PhA samples at 5 wt. % concentration when solvent extraction is used versus the derivatization reagent is applied directly to the solid sample and derivatized. There are not significant qualitative chromatographic differences between the chromatograms in the solvent extraction versus direct derivatization cases that were performed in the laboratory, with the exception of some additional peaks in the direct derivatization chromatograms which come from the higher derivatization temperature and therefore increased number of derivatization byproducts.

There is an order of magnitude increase in the organic response for Glu and Phe with solvent extraction in comparison to direct derivatization. The difference in response between solvent extraction and direct derivatization partially explains the high limit of detection calculated in Section IV.3.2.2.3 since the entirety of the organic content in the sample is clearly not being extracted in the case of the direct derivatization. In order to justify a semi-quantitative comparison between the experiments conducted with solvent extraction versus direct derivatization, the quantity of moles sent to the GC column based on each sample handling and derivatization procedure should be considered. The quantity of moles sent to the GC column is ~2-4 nmol of each organic compound for solvent extraction and ~1 nmol for direct derivatization. This calculation considers the organic concentration of the sample, the amount (mg) of sample utilized for a test, dilution based on the derivatization reagent solution, and the split ratio of the GC. Part of the explanation for the higher chromatographic response can be due to a slightly higher quantity of moles which is sent to the GC, but this does not account for the order of magnitude difference (or more) in the response for Glu and Phe. It is also challenging to quantify the peak area of pyroglutamic acid, 2tBDMS, because this peak is not sharp and blends with the derivatized Glu peak. This could also interfere with the peak area measurement reported in Section IV.3.2.2.3. The lack of repetition of tests using solvent extraction does not allow for a robust quantitative comparison between the two protocols. Additionally, the chromatograms for the solvent extraction tests were saturated, which interferes with quantification. However, it is clear that the direct derivatization protocol, which more closely mimics that of the space experiment, is less efficient than the traditional laboratory technique using solvent extraction.

This effect for PhA is less pronounced and may be due to a difference in the extraction efficiency of specific extraction solvents for carboxylic acids versus amino acids. Phthalic acid is polar and known to be soluble in water (at least at high enough temperatures). However, based on the water temperature of the solution used here, perhaps phthalic acid is only partially dissolved and would be more efficiently extracted with an alcohol-only solution rather than the H2O/isopropanol (1:1) solution used in this study. Studies have shown efficient extraction of carboxylic acids using alcohol-only extraction solvents. For example, only trace levels of benzoic acid, which also has a polar carboxylic acid group, were detected in a water extract in previous studies while it had a much higher response in an isopropanol-only extraction solvent [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF].

Another well-accepted laboratory and in situ extraction technique is ultrasonic extraction, in which high-frequency sound is applied to liquids, producing a cavitation process which accelerates both chemical and physical reactions. A sonification step added to the solvent extraction technique can provide more efficient contact between solid and solvent than the common shake-flash method which is used in this study, resulting in a greater recovery of the analyte. While sonification has not been and will not be used to support GC-MS experiments on surface missions to Mars, it has been shown that the solvent extraction technique on its own is not capable of achieving a significant recovery of amino acids in an Atacama Desert sample, even after 1 hour of interaction between sample and solvent. In this case, ultrasonic extraction was necessary to accelerate the extraction process and to detect amino acids in the sample [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]). Therefore, it can be considered that the solvent extraction, while more efficient than direct derivatization, does not have a 100% efficiency and the low limits of detection (on the nmol level) are explained by this extraction efficiency factor.

Solvent extraction is a useful technique for analysis of samples relevant for planetary environments, because it allows for an efficient extraction and characterization of samples, especially for unknown samples or samples with little prior characterization. However, the MOMA space experiment does not carry solvents for extraction and does not enable this method of extraction. As discussed previously, MOMA will use a pre-heating of the sample to aid in extraction of organics via thermodesorption, a protocol which will be further discussed in Chapter V.

IV.3.2.2.2. MTBSTFA derivatives

MTBSTFA derivatization in the presence of DMF has been shown to have an efficient reaction yield, in the range of 90-100%, with amino acid chemical standards [START_REF] Rodier | Detection of martian amino acids by chemical derivatization coupled to gas chromatography: In situ and laboratory analysis[END_REF]. For MOMA, MTBSTFA is nominally implemented with the MXT-5 or MXT-CLP GC columns, which will allow for the highest heating of the column (up to about 250˚C), therefore higher molecular weight compounds can be expected during a nominal run (Chapter III). In this study, tBDMS derivatives of Glu, Phe, and PhA were clearly detected at all three concentrations using both solvent extraction and direct derivatization. Derivatized AMP or degradation products (derivatized or not) associated with AMP were not identified with the 5 wt. % Mont+AMP sample using both solvent extraction and direct derivatization.

Table 19 lists the main silylated organic compounds that are detected with MTBSTFA derivatization of Glu, Phe, and PhA (Figure 58). The main derivatization product of each organic compound is its fully silylated product: Glu with three tBDMS groups, PhA with two tBDMS groups, and Phe with two tBDMS groups. The only parent organic compound which generates multiple derivatized products is Glu, for which pyroglutamic acid, 2tBDMS, is also identified.

Pyroglutamic acid is a derivative of glutamic acid in which the free amino acid group cyclizes to form a lactam or a cyclic amide and is identified in both solvent extraction and direct derivatization tests. This compound could have been produced during storage of the samples. Studies have shown that amino acids such as glutamine are converted into pyroglutamic acid almost completely during prolonged storage in HCl and that non-significant quantities of pyroglutamic acid were produced from MTBSTFA derivatization of glutamine which was performed at 75˚C for 30 min [START_REF] Woo | Capillary gas chromatographic determination of proteins and biological amino acids as N(O)-tert.-butyldimethylsilyl derivatives[END_REF]. Pyroglutamic acid could also have been produced during the derivatization reaction itself in the direct derivatization study since the MTBSTFA derivatization reaction temperature is higher (250˚C). Amino acid thermal stability can vary greatly. For example, levels of 1% undecomposed amino acid were detected at 500°C for proline, at 600°C for glycine, and at 700°C for valine and leucine, while alanine was found undecomposed at 0.4% level even at 800°C [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF]. Glutamic acid has one of the lowest thermal stabilities and has been shown to be completely decomposed after pyrolysis at 400˚C. Also, pyrolysis at 300˚C of glutamic acid has shown to generate pyroglutamic acid by water elimination as one of its main pryolysates and takes place by the reaction shown in Figure 59 and proposed by [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF].

However, while it is possible that pyroglutamic acid is produced during the derivatization reaction at higher temperatures, pyroglutamic acid was also detected in the solvent extraction tests for which derivatization was performed at 75˚C for 15 min. Therefore, it is more likely that the pyroglutamic acid was produced during storage of the samples. It may be that the contribution of pyroglutamic acid by the derivatization process is significant in the direct derivatization tests due to the higher derivatization temperature, but this has not been quantified due to the unknown quantity of pyroglutamic acid (wt. %) in the samples prior to derivatization, the lack of repetition of the solvent extraction tests, and that the chromatographic peaks of the pyroglutamic acid and glutamic acid derivatives were difficult to deconvolute in the chromatogram from the solvent extraction tests.

In both a solvent extraction test and a direct derivatization test with Mont+AMP, 5 wt. % samples, derivatized AMP is not detected with MTBSTFA derivatization during the 37 min run time. This is expected since it has four alcohol functions and one amine function, which would result in a high molecular mass after MTBSTFA derivatization and would likely have a longer retention time than the tested run time. A detection of this molecule may be limited by its retention time, its ability to elute from the GC column, or its fragmentation pattern, if the mass of important fragments is higher than the 21-535 Dalton range of the mass spectrometer in these tests. It is also possible that the AMP molecule undergoes fragmentation and/or rearrangement during the derivatization reaction and subsequent derivatization of molecular fragments such as adenosine or adenine. A directed search was performed for adenine, 2tBDMS (C17H33N5Si2) which has a base peak at m/z 306 and was not found. It is also possible that products related to AMP were not detected due to either the effectiveness of the H2O/isopropanol (1:1) solution as an extraction solvent (in the solvent extraction tests) for this molecule, to the efficiency of extraction of the molecule from the mineral matrix in the direct derivatization tests, and/or to partial deactivation of the derivatization reagent in the presence of the clay mineral.

The effectiveness of an H2O/isopropanol solution for extraction of AMP should also be further considered. NIR results of the Mont+AMP samples indicated that the amino group of the adenine moiety is mainly involved in the interaction with the mineral [START_REF] Fornaro | UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples: the case of Phthalic Acid, Adenosine 5'-Monophosphate, L-Glutamic Acid and L-Phenylalanine Adsorbed onto the Clay Mineral Montmorillonite in the Presence of Magnesium Perchlorate[END_REF], which is supported by other studies of the molecule-mineral interaction of AMP adsorbed to montmorillonite [START_REF] Villafañe-Barajas | Salinity Effects on the Adsorption of Nucleic Acid Compounds on Na-Montmorillonite: a Prebiotic Chemistry Experiment[END_REF]. Studies of adenine adsorbed to montmorillonite show that desorption efficiency of adenine from the montmorillonite was 78 to 88% with a potassium hydroxide (KOH) solution, and only 4.1 to 6.6% using distilled water/CaCl2 and Mehlich-1 (HCl/H2SO4) extractors [START_REF] Baú | Adenine Adsorbed onto Montmorillonite Exposed to Ionizing Radiation: Essays on Prebiotic Chemistry[END_REF]. Of course, in contrast to adenine, a nucleotide such as AMP would interact also by the phosphate group with the hydroxyl groups from the edge sites of the montmorillonite and electrostatic interactions might occur [START_REF] Feuillie | Adsorption of nucleotides onto Fe-Mg-Al rich swelling clays[END_REF][START_REF] Villafañe-Barajas | Salinity Effects on the Adsorption of Nucleic Acid Compounds on Na-Montmorillonite: a Prebiotic Chemistry Experiment[END_REF]. Studies have also shown that the adsorption of AMP on montmorillonite is affected by the absence of a buffer or salt [START_REF] Ferris | The adsorption and reaction of adenine nucleotides on montmorillonite[END_REF], therefore it would be interesting to test the Mont+AMP samples with and without Mg-perchlorate in order to study these effects. The far fewer number of molecules and the preservation of the organic compounds (i.e. glutamic acid, phenylalanine, phthalic acid) in comparison to the pyrolysis results in the previous section demonstrate the advantages that derivatization chemistry provides to GC-MS analyses of compounds. The synergy between pyrolysis and derivatization will be further discussed in Section IV.3.3.1.

IV.3.2.2.3. Chromatographic response across organic concentrations

The Mont+Glu, Mont+PhA, and Mont+Phe samples were run at all three concentrations (5 wt. %, 1 wt. %, and 0.1 wt. %) with three repetitions using direct derivatization. In this section the variability in the chromatographic response across these three organic derivatives and across three concentrations on COTS GC-MS hardware are discussed. Figure 60 shows a comparison of the chromatographic response of the three organic derivatives across three concentrations in XIC since the derivatives for the 0.1 wt. % samples are only visible using XIC. Table 20 presents the chromatographic response in total ion current (TIC) for each derivative across the three concentrations.

The peak area of each eluted compound is plotted as a function of the amount of product injected to the GC column in Figure 61. Each point in the plot represents the mean value of three replicate measurements and the standard deviations are represented as error bars on the plot. Considering the molar mass of each compound, a syringe injection of 0.5 µL, and a split ratio of 50, about 0.03 to 1 nmol of each compound were sent to the GC column depending on the compound and the derivatized glutamic acid with DMF-DMA derivatization [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF], which may also be the same for MTBSTFA derivatization, likely due to the aromatic side group of Phe.

Figure 61: Log/log scale response of the chromatogram (area of the peak) depending on the quantity of organic compound injected (nmol) to the GC column. MTBSTFA/DMF derivatization (250˚C, 3 min) was performed directly on montmorillonite samples doped at three concentrations (5 wt. %, 1 wt. %, and 0.1 wt. %) of an organic compound (Glu, Phe, or PhA). The quantity of organic compound injected to the GC column depends on the amount of the sample used in a test, the dilution when the derivatization reagent is applied, the amount of the solution injected to the GC injector by syringe after offline derivatization, and the split ratio of the GC. Each point represents the mean of 3 repetitions. The x-axis error bars show the range in injection quantities based on the number of moles of the organic compound sent to the GC column, which is based on the original amount of soil sample taken (in mg) and assuming a 100% extraction efficiency of the organic compound from the mineral matrix as well as a 100% transfer rate of the sample across the sample handing protocol.

The derivatives for the 0.1 wt. % samples are only visible in XIC at specific ions. In some cases, (Glu and Phe), the base peak (m/z 73) is obscured by background. Therefore, for the chromatographic response values (for TIC), a lower response for diagnostic mass fragment values, including the base peak for Glu and Phe, are calculated based on measured peak areas for higher mass values. Part of the background which obscures important mass peaks for these compounds is from the MTBSTFA background itself (m/z 73 and m/z 147). Since disiloxane, 1,3-bis(1,1dimethylethyl)-1,1,3,3-tetramethyl-(monosilylated water) has important peaks at m/z 73 and m/z 147, background interference from the sizable presence of water in the clay mineral may be minimized by drying of the sample prior to derivatization. However, this kind of background is known to be present at sizable quantities on SAM. Therefore, it must be expected that MOMA will deal with similar interference in the GC-MS mass spectra, though to a less extent, since SAM uses 500 µL of derivatization solution for a given derivatization experiment while MOMA uses 15 µL per experiment. Amount to GC (nmol)

Table 21 shows limit of detection (LOD) and limit of quantification (LOQ) for each compound.

The detection and the quantification limits were computed as X LOD = 3.3/i/S and X LOQ = 10/i/S where /i is the standard deviation of the intercept of the linear fit. These values are much higher than previously reported LOD on derivatized chemical standards of amino acids and nucleobases which are 0.4-49.8 pmol for DMF-DMA derivatization of amino acid standards [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]), 0.03-5 pmol for MTBSTFA derivatization of amino acid standards [START_REF] Rodier | Detection of martian amino acids by chemical derivatization coupled to gas chromatography: In situ and laboratory analysis[END_REF], and 3-12 pmol for MTBSTFA derivatization of nucleobases [START_REF] Glavin | Sublimation extraction coupled with gas chromatography-mass spectrometry: A new technique for future in situ analyses of purines and pyrimidines on Mars[END_REF]). The detection limits given in Table 21 may be an overestimation of the detection limit of a given organic compound, since the calculation of the amount of an organic compound sent to the GC assumes that all of that organic compound in the sample is both extracted and derivatized. With more efficient extraction, the limit of detection values might be decreased. Techniques to aid organic extraction in lab tests (solvent extraction, sonification) and on the space instrument (thermal desorption) will improve the chromatographic response. Indeed, our results with the same samples and solvent extraction technique yield about an order of magnitude higher response (Section IV.3.2.2.1). The detection limit of glutamic acid in particular may be shifted upward due to the breakdown of part of glutamic acid into pyroglutamic acid which also undergoes MTBSTFA derivatization and is not considered in the calculation. This result demonstrates a tradeoff with the idea of increasing the derivatization temperature in order to aid extraction of compounds from a mineral matrix, since it shows that even for derivatization temperatures, which are comparatively lower than thermochemolysis temperatures, molecules can begin to break down into multiple compounds which results in a lower limit of detection for individual target molecules. These results also suggest that the detection of organics, even organics partially adsorbed to a mineral matrix, and unaided by extraction techniques, can shift the limit of detection in relationship to standards by orders of magnitude.

Non-detection or lower responses of target compounds in the presence of a mineral matrix can also be due to either deactivation of the MTBTSFA derivatization reagent or to an interaction between the mineral matrix and the target molecules and/or their derivatives [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF]. Chemical deactivation of MTBSTFA by the presence of the mineral matrix may occur if MTBSTFA reacts preferentially with other species such as non-structural water, -OH groups present in minerals (structural water), or salts. A destructive interaction between organic molecules or derivatives during the extraction/derivatization procedure may occur through hydrolysis (linked to the presence of non-structural or structural water) or oxidation (e.g., in the presence of iron oxides or perchlorate salts). Labile hydrogens of targeted organic molecules may also bond to the silicon atom of soil samples, resulting in a non-availability of organic molecules for derivatization. When derivatization is applied directly on the soil sample, as it is here, these effects can occur in combination and affect the derivatization yield. The effect of the mineral matrix on the derivatization reaction itself was studied by [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF], who proposed a set of experiments to distinguish causes of a non-detection or lower yield. A study of a predominantly smectite clay, collected during the AMASE campaign (Section III.2.1.4), showed a significant derivatization yield decrease only for glycine (out of a set of 17 amino acids) and a difference in yield compared to other amino acid chemical standards ranging from 62.5% (lysine) to 106.2% (isoleucine) [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF]. In the study by [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF], the presence of a hydrated mineral led to a reduction in the derivatization yield (with certainty only for glycine), but not a zero yield. This result is consistent with the results shown here, in that it is possible to detect MTBSTFA derivatives in the presence of a smectite clay, however with higher detection limits than for chemical standards. Whether or not this is due to the extraction efficiency and/or a partial deactivation or interference of the derivatization reaction can only be answered through additional directed and quantitative tests. For example, in these samples, there is organic background and water that may interact preferentially with MTBSTFA. Studies with chemical standards at the same concentrations as present in the samples could elucidate the quantitative decrease in the reaction yield of MTBSTFA in the presence of this mineral matrix and is proposed in the Conclusions section (Section IV.4).

IV.3.2.3. DMF-DMA derivatization

This section will discuss DMF-DMA derivatization of the samples. First, the DMF-DMA derivatization products will be discussed (Section IV. 3.2.3.1). Next, a limited optimization of the temperature and duration of the DMF-DMA derivatization reaction with these samples is discussed along with experimental limitations of offline derivatization optimization coupled to small sample sizes (Section IV.3.2.3.2). DMF-DMA derivatization tests were performed only with direct derivatization (no solvent extraction). DMF-DMA derivatization was performed at three different temperatures (140˚C, 200˚C, and 250˚C) in order to try and improve the extraction efficiency of the organic compounds from the mineral during the direct derivatization. The expectation is that increasing temperature will correspond to increasing extraction efficiency, which is shown to be the case in Figure 62.

IV.3.2.3.1. DMF-DMA derivatives DMF-DMA derivatization was first performed at 145˚C for 3 min, which is the programmed reaction protocol for DMF-DMA on MOMA. These baseline DMF-DMA derivatization parameters were chosen based on optimization of the derivatization protocol on amino acid chemical standards and also to avoid racemization of chiral compounds of astrobiological interest [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF][START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. Due to the lower reaction yield of DMF-DMA compared with MTBSTFA, it is challenging to detect the DMF-DMA derivatized organic compounds under the nominal MOMA derivatization parameters, 145˚C for 3 min, even for the 5 wt. % samples.

Table 22 shows the main organic compounds that result from DMF-DMA derivatization and are identified after targeted searches, often aided by an extracted-ion chromatogram (XIC). The 5 wt. % samples were first run on a GC Trace Ultra coupled to an ISQ mass spectrometer which is older and has higher instrument background. Derivatized Glu was not detected after derivatization at 140˚C, but is detectable in XIC after derivatization at 200˚C and 250˚C. Derivatized Phe and PhA are detected close to the background signal after derivatization at 140˚C and the peak shape is distorted by interreference from the noise, resulting in wide tailing peaks (e.g., Phe 5 wt. %) or a broader background (e.g., PhA 5 wt. %). There is also some observed peak shifting due either to a low signal-to-noise (S/N) ratio, since this shifting was not observed in tests under the same conditions in which the S/N ratio was higher, or due to experimental error from the manual syringe injection. Based on the number of repetitions performed, it is not possible to say definitively. Derivatized Phe and PhA are detected in the TIC when the derivatization temperature is increased to 200˚C and 250˚C and the peak shape is improved. The 1 wt. % samples were run on a newer GC Trace coupled to an ISQ in which the background level is lower. The tests on this instrument yielded detection of all three derivatized organic compounds at all three tested derivatization temperatures as shown in Figure 63. Even if the resulting molecule of DMF-DMA derivatized AMP may have a lower molecular weight (likely 4 methylations, 1 dimethylformamidination), derivatized AMP was not detected with DMF-DMA derivatization. The discussion of the detection of AMP with MTBSTFA derivatization (Section IV.3.2.2.2) applies to DMF-DMA as well, and further testing to understand why derivatives were not detected are proposed in the Conclusions section (Section IV.4). A higher amount of sample (~10 mg) was used in the tests with the 1 wt. % samples than with the 5 wt. % samples (~5 mg). Due to the challenge to detect the organic compounds with DMF-DMA, chemical standards of Phe, Glu, and PhA were run with DMF-DMA derivatization at 200˚C for 3 minutes at high concentrations in order to ascertain the retention time(s) of derivatives. The concentration of the organic acid solutions was not quantified. Derivatization and subsequent GC-MS analysis of Phe, Glu, and PhA chemical standards generates multiple species per parent organic compound (Figure 64, Table 22). In general, multiple species are expected from the derivatization reaction and can be attributed to a molecular rearrangement of the molecule in the gas phase or to an incomplete derivatization of the parent molecule. Table 22 shows the DMF-DMA derivatization byproducts and their retention times which were used to conduct directed searches using XIC. For the montmorillonite samples doped with organics, the most prominent peak (largest peak area) within the reference spectra was chosen as the reference peak which was used to identify a detection of the organic compound at a given concentration level. In almost all cases, only this peak was resolvable from the noise with the exception of the phthalic acid sample in which both dimethyl phthalate and 2-methoxyethylmethyl phthalate were visible in the chromatogram. 1) dimethyl phthalate, ( 2) methyl-L-phenylalanine, N-dimethyl-, methyl ester, ( 3) Lglutamic acid, N-dimethylaminoethylene-, dimethyl ester, ( 4) possibly 2-methoxyethylmethyl phthalate, ( 5) N-formyl phenylalanine, methyl ester, (6) L-phenylalanine, N-dimethylaminomethylene-, methyl ester, ( 7) 5-ethoxy-2-phenyl-3H-imidazol-4-carboxylic acid, methyl ester. The GC column was held at 40˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.0 mL•min -1 .

The challenge to detect these organic compounds with DMF-DMA derivatization at relatively high concentrations and on laboratory COTS GC-MS may pose a challenge for the detection of chiral enantiomers on Mars, since it is expected that COTS GC-MS would have a lower limit of detection than that of the flight model and organic concentration in martian samples may be well below 5 wt. % or 1 wt. %. Additionally, the apparent relationship between detectability and derivatization temperature may pose a risk for racemization if derivatization should occur at higher reaction temperatures. In a study of amino acid standards with DMF-DMA derivatization, it was found that at higher reaction temperatures (160˚C), a high percent yield of racemized products occur [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF]. Several amino acids experienced partial racemization while only one amino acid in the study (tyrosine) displayed complete racemization. While partial derivatization generated by derivatization may not pose a problem for space applications, since the initial value of enantiomeric excess can be back-calculated if the racemization rate is well determined, the high temperature regime of the study with chemical standards (160˚C) is well below the derivatization temperatures (200-250˚C) needed for detection of organic compounds in the presence of a mineral matrix shown here. Doped samples also provide a best-case scenario in terms of the integration of the organic compound because at best the organic matter is only partially adsorbed onto the mineral walls and interlayers. Finally, this study is not optimized for the detection of the organic compounds in that ( 1) no dedicated extraction step is performed (e.g., thermodesorption) before derivatization and (2) offline derivatization is performed in which only a portion of the extracted and derivatized organics are injected to the GC. In the case of MOMA, derivatization is performed If MOMA sample sizes were utilized in an online derivatization scenario in the laboratory with the same sample and GC parameters, on the order of 700 nmol of Glu would be sent to the GC. In addition, the ratio between the sample quantity and the derivatization reagent quantity are quite different between the space experiment and these laboratory tests (i.e., 5 mg of sample in the laboratory and 100 mg of sample in the flight experiment, with 15 µL of derivatization reagent applied in both cases). The practical challenges to sample sizes per experiment of this size include (1) the precious nature of martian analog samples (linked to availability of such samples), ( 2) the large amounts of total sample needed for proper experimental redundancy, buffer, and testing multiple variables ( 3) and, for this type of multi-technique analysis specifically, the multiple number of instrument teams over which samples sizes are distributed (and linked to the need for characterization data of samples in order to robustly interpret GC-MS results). Improvement of lab capabilities for online derivatization and optimization of organic extraction and wet chemistry protocols for solid samples in the context of MOMA are further discussed in Chapter V.

IV.3.2.3.2. DMF-DMA derivatization protocol with solid samples

Derivatization temperature and duration for DMF-DMA

The absence of sonification or solvent extraction on MOMA and the potential levels of organics on Mars well below those in this set of samples cannot be modified. However, parameters that can be modified in order to improve the chromatographic response of target compounds include the temperature and the duration of the first two parts of the MOMA in situ technique: ( 1) opportunistic extraction of organic matter from the solid sample by low-temperature thermodesorption (limited by the temperature release of the derivatization reagent from the MOMA capsules) and ( 2) chemical derivatization of the extracted organics to produce volatile species. These parameters have been partially optimized for chemical standards [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF][START_REF] He | Application of TMAH thermochemolysis to the detection of nucleobases: Application to the MOMA and SAM space experiment[END_REF]), but have not been optimized for compounds partially or fully adsorbed to the mineral matrix of solid samples. Using remaining 1 wt. % samples, the DMF-DMA derivatization temperature was varied (derivatization reaction at 140˚C, 200˚C, and 250˚C for 3 minutes), since there was a challenge to detect the organic compounds with DMF-DMA and an increased temperature demonstrated a higher response in initial tests with 5 wt. % samples on a different instrument.

The trend in response for derivatized Phe and PhA are consistent with an increased response with increasing derivatization temperature as seen in the case of the 5 wt. % samples (Figure 63). There was not a significant increase in the response for derivatized Glu with increasing DMF-DMA derivatization temperature, which is not consistent with the increase in response from derivatized Glu with increasing derivatization temperature for the 5 wt. % samples. This could be due to a lack of test redundancy in the case of the 5 wt. % samples or to a difference in the adsorption of organics to the mineral in the 5 wt. % versus 1 wt. % samples.

Experimental limitations for offline derivatization and small sample sizes

An additional batch (Batch 2) of montmorillonite samples doped with Glu, Phe, and PhA were procured from Teresa Fornaro (Istituta Nazionale di Astrofisica (INAF); Florence, Italy). Total sample sizes of each doped sample were on the order of 50 mg. These samples were used to conduct optimization studies of derivatization temperature and duration. However, since these kinds of studies require tests at a range of temperatures and durations and combinations of a given temperature and duration, in addition to redundancy of tests, the number of tests is large and the sample size for each test is small, ~2-3 mg per test. For example, Figure 66 shows tests that were conducted on Mont+Phe, 5 wt. % derivatized with DMF-DMA at four temperatures (140˚C, 170˚C, 220˚C, and 260˚C) for 10 minutes and tests conducted on Mont+PhA, 5 wt. % derivatized with DMF-DMA for four durations (45 sec, 3 min, 5 min, and 10 min) at 220˚C. These tests required about 40 mg and 45 mg respectively assuming a 3 mg sample size per test. The combination of offline derivatization and small sample sizes for lab testing of optimization studies have at least the three following experimental limitations: (1) very small organic content reaches the GC column for analysis, (2) challenge to extract liquid content after derivatization and centrifugation due to large ratios of soil to liquid components, and (3) inconsistent mixing of internal standard with solution prior to GC injection. Additionally, (4) it is debatable how appropriate synthetic clay samples doped with organics are for optimization studies, since organics doped onto synthetic samples may be better characterized by a partial adsorption to mostly external surfaces rather than adsorption and chemisorption to both external and interlayer spaces as in natural clay samples. There have been preparation methods proposed for the intercalation of organic matter into the interlayer spaces of montmorillonite through cation-exchange in order to compare behaviors of organic matter related to its location at different surface sites of the clay mineral (e.g., [START_REF] Liu | Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals[END_REF]. As previously discussed, offline derivatization allows for a much smaller number of moles of each organic compound to be introduced to the GC column (1). In order to mitigate this challenge, very small amounts of derivatization reagent are applied directly to the solid sample in order to keep the dilution ratio high. However, due to the small amount of derivatization reagent which is applied, much of the derivatization reagent is absorbed by/or condenses on the solid sample prior to and after derivatization so that sufficient liquid is not released, even after centrifugation, in order to extract from a supernatant via liquid syringe (2). Additionally, the amount of liquid which is held by the soil (liquid holding capacity) post-derivatization appears to vary depending on the derivatization temperature and duration, so that even when there is available solution, adding an internal standard as a post-derivatization step, in order to safeguard it from the derivatization reaction, results in an inconsistent mixing ratio between the solution and the internal standard across derivatization parameters. Test solutions were implemented for subsequent tests on a natural sample (Chapter V) including to (1/2) utilize a laboratory-based online derivatization setup, (2) select samples for which there are larger total sample sizes, (3) apply the internal standard to the derivatization reagent in solution prior to derivatization, and (4) select a well-characterized natural sample with a suite of target compounds (Chapter V).

IV.3.2.4. TMAH thermochemolysis

Thermochemolysis is a complimentary capability to derivatization chemistry since it allows the analysis of refractory and/or insoluble matter in complex matrices (Geffroy- [START_REF] Geffroy-Rodier | Thermochemolysis in search for organics in extraterrestrial environments[END_REF]. This section will discuss the thermolysates of the samples under TMAH thermochemolysis at 600˚C for 30 s. At these temperatures, thermal degradation of organic compounds results in the loss of their functional groups (e.g., decarboxylation, deamination, dihydroxylation) then by dehydrogenation, cyclization, and aromatization of molecules. Figure 67 shows the thermolysates from the four organic molecules under investigation in the presence of the montmorillonite mineral. The main products for AMP are 9H-Purin-6-amine, N-9-dimethyl and 9H-Purin-6-amine, N,N-9trimethyl which are methylated forms of adenine, the nucleobase component of AMP. The secondary amine is methylated in both cases, while the primary amine is mono-or di-substituted.

The TMAH thermochemolysis of PhA produces a greater number of products than in the pyrolysis test, likely due to the combination of pyrolysis products and chemically altered products by TMAH. The thermochemolysis of PhA methylates the carboxylic acid functional groups to form an ester, but this product is not the most prominent in the chromatogram under these test conditions. Benzoic acid, methyl ester and phthalimide, N-methyl-are both formed at higher quantities than the aforementioned ester. At temperatures higher than 450˚C, a decarboxylation process starts with the formation of CO2, benzoic acid, and benzene [START_REF] Moldoveanu | Pyrolysis of organic molecules with applications to health and environmental issues[END_REF]. Benzoic acid is identified in the chromatogram at lower levels than benzoic acid, methyl ester; benzoic acid, methyl ester is likely formed by decarboxylation from thermal degradation coupled to methylation by TMAH. Benzoic acid is also a known degradation product of Tenax on SAM, so these additional products which are prominent in the chromatogram and yet represent a thermochemolysis of the more intact parent molecule provide the necessary information to perform direct searches and more strictly identify the presence of carboxylic acids and amino acids in more complex natural samples.

As for the pyrolysis results, the thermochemolysis of Phe produces the greatest number of byproducts, which are mainly a suite of aromatic compounds. Major products of Phe include toluene, ethylbenzene, styrene, benzylnitrile, and 2,6-diphenyl-pyridine. Methylated products are present at lower levels, including hydrocinnamic acid, methyl ester and phenylalanine, N,Ndimethyl-, methyl ester. Several of the largest peaks in the chromatogram (toluene, ethylbenzene, styrene) are compounds that can also be generated from Tenax trap degradation on SAM and MOMA [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. A laboratory setup which utilizes adsorption/thermal desorption trapping with Tenax is discussed in Chapter V.

The main products of Glu include L-glutamic acid, N,N,-dimethyl-, dimethyl ester as well as 3-(dimethylamino)-phenol and L-proline, 1-methyl-5-oxo-, methyl ester. The methylation is observed on both carboxylic acid functional groups and on the amine and is the most prominent peak in the chromatogram, which presents a good example of how TMAH thermochemolysis can produce different derivatives than DMF-DMA derivatization (L-glutamic acid, Ndimethylaminomethylene-, dimethyl ester) where the amine was dimethylformamidinated. Lproline, 1-methyl-5-oxo-, methyl ester is likely formed from a cyclisation as proposed in [START_REF] Gallois | Pyrolysis-gas chromatography-mass spectrometry of the 20 protein amino acids in the presence of TMAH[END_REF].

The thermochemolysis of amino acid standards has been covered in the literature [START_REF] Choi | Dimerization reactions of amino acids by pyrolysis[END_REF], 2011;[START_REF] Gallois | Pyrolysis-gas chromatography-mass spectrometry of the 20 protein amino acids in the presence of TMAH[END_REF]). [START_REF] Gallois | Pyrolysis-gas chromatography-mass spectrometry of the 20 protein amino acids in the presence of TMAH[END_REF] found that of the 20 proteinaceous amino acids, methylation is the major process for all but four amino acids. [START_REF] Gallois | Pyrolysis-gas chromatography-mass spectrometry of the 20 protein amino acids in the presence of TMAH[END_REF] established mechanism categories for the formation mechanisms undergone by each of the 20 proteinaceous amino acids in TMAH thermochemolysis and showed that there is a co-occurrence of different mechanisms for a given amino acid (Figure 68). The results of this thesis chapter are consistent with the main proposed formation mechanisms of the observed products of Phe (direct methylation, homolysis, and decarboxylation) and Glu (direct methylation, cyclisation). Due to the higher temperature at which the thermochemolysis reaction is performed (600˚C) compared with the derivatization reactions (140-250˚C), more byproducts from the presence of the organic compound itself are observed. This presents a challenge to tracing back to the parent molecule, especially for carboxylic and amino acids as it is shown here can degrade into products similar to those produced from degradation of the injection traps used on both SAM and MOMA. However, it is important to continue to build up chromatographic libraries of a large range of molecules across the three wet chemistry techniques, since many elements go into the decision making of which reagent will be run first on Mars, as can be attested by the experience learned from Curiosity's SAM instrument. The larger the laboratory databases for all three wet chemistry protocols, the more opportunistic for the interpretation of data that is eventually procured on Mars or on ETU or testbed models of MOMA. MOMA GC-MS experiment and if so, in determining the GC parameters. For example, if LD-MS detects labile hydrogen and polar compounds, MOMA may proceed to derivatization-GC-MS, while if LDMS detects heavier molecules, MOMA may proceed to pyrolysis-GC-MS or TMAH thermochemolysis-GC-MS. A sample sufficiently rich in bound water (e.g., clay minerals) could inhibit the MTBSTFA or DMF-DMA reaction. In this case, TMAH may be utilized, since it is relatively immune to water (Section I. 3.1.2.4). If heavier compounds such as macromolecules are detected, thermochemolysis and pyrolysis would likely be used to reach the most refractory compounds of the sample [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. Subsequently, the detection of small byproducts in a pyrolysis experiment may drive the decision to proceed to a GC-MS analysis utilizing derivatization. In this way, not only are the LD-MS and the GC-MS techniques synergistic, but the different sub-modes of the GC-MS capabilities (pyrolysis, derivatization, thermochemolysis) are synergistic as well.

Sample Pyrolysis

MTBSTFA DMF-DMA TMAH Mont+AMP ‡ ND ND † Mont+PhA †,+ † † †, ‡ Mont+Phe ‡ † † †, ‡ Mont+Glu ‡ †, ‡* † †, ‡

IV.3.3.2. Comparative efficiency of derivatization and thermochemolysis reactions

Only MTBSTFA derivatization was performed with redundancy on samples at all three concentrations, while DMF-DMA derivatization and TMAH thermochemolysis tests were run once and largely on the 5 wt. % samples with the aim to show the qualitative products produced by these reactions. An exception is Mont+PhA which was run at all three concentrations with TMAH thermochemolysis. Table 24 and Figure 69 summarize the chromatographic response across samples, derivatization reagents, and concentrations. Since MTBSTFA/DMF-DMA and TMAH tests were performed on two separate instruments respectively, the chromatographic response between derivatization and thermochemolysis cannot be directly compared due to differences in mass spectrometer performance and/or instrument background. However, all tests were conducted on the same ThermoScientific GC Trace Ultra/ISQ model, and can be generally compared. Additionally, D8-naphthalene as an internal standard, which should generally be employed to improve the precision of quantitative analysis, was used only for some of the DMF-DMA and for the TMAH tests. Therefore, the chromatographic response across all techniques and the available A/AIS are shown in Table 24. It is also determined that chromatographic response values can be compared across tests since the peak area of derivatization byproducts is consistent across runs.

Table 24 and Figure 69 show that the comparative derivatization efficiency between MTBSTFA and DMF-DMA can vary depending on the compound. In the case of Glu and PhA, MTBSTFA yields an order of magnitude or more increased response than DMF-DMA, while for Phe, the yields for MTBSTFA and DMF-DMA (both at a derivatization temperature of 250˚C) are similar. An increase in derivatization temperature for DMF-DMA improves the yield; however, as discussed in Section IV.3.2.3, higher derivatization temperatures for DMF-DMA may not be advisable due to the risk of racemization. Additional variables can also affect the measured response, such as variability in the adsorption of the organic compound to the mineral matrix and the related extraction efficiency. Further testing should have redundancy and use a natural sample or a synthetic sample which has been demonstrated to mimic the integration of organics to the mineral matrix of a natural sample.

TMAH produces a suite of products from a single organic compound, representative reaction products are chosen (i.e., L-glutamic acid, N,N,-dimethyl-, dimethyl ester; Pyridine, 2,6-diphenyl; Benzoic acid, methyl ester and Phthalimide, N-methyl) to quantify. For the TMAH thermochemolysis of glutamic acid and AMP, the most prominent peaks (largest peak area) in the chromatograms are the directly methylated products. However, this is not the case for the TMAH thermochemolysis of phenylalanine and phthalic acid, for which the most prominent peaks are styrene and benzoic acid, methyl ester, respectively. In the quantitative comparison shown in Figure 69, these peaks are quantified as well as peaks that are considered to be more representative of the parent molecule, such as the directly methylated products of phenylalanine and phthalic acid. While they are more representative of the parent molecule, they will have a lower sensitivity. The responses from these byproducts also vary with similar behaviors to those of MTBSTFA and DMF-DMA derivatization, with the response of the main byproduct of TMAH thermochemolysis of Glu at an order of magnitude below that of the response from the main byproducts of Phe and PhA.

Another important difference between the derivatization and thermochemolysis tests is the "offline" (derivatization) versus "online" (thermochemolysis) instrument setups of the tests. The derivatization tests are performed "offline," in which 15 µL of the derivatization reagent is applied to the sample size (~5 mg) and the reaction is performed externally to the GC-MS instrument before a small quantity of the derivatized extract (0.5 µL) is injected to the GC by syringe. The TMAH tests are performed "online," in which the entire sample size (~5 mg) and the chemical reagent are pyrolyzed and introduced to the GC column (with some material vented via the split settings). Therefore, in addition to being run on different instruments, a direct comparison between the TMAH and MTBSTFA responses is not appropriate, since ~30 nmol of organic compound is sent to the GC column (TMAH) in comparison to ~1 nmol (MTBSTFA/DMF-DMA) in the case of the 5 wt. % samples.

Figure 69 compares the efficiency of MTBSTFA/DMF and DMF-DMA derivatization and TMAH thermochemoysis of three organic compounds (Glu, Phe, PhA) in the presence of montmorillonite.

The results are still consistent then with the idea that MTBSTFA derivatization in the presence of DMF has the highest reaction efficiency of the three chemical reagents for amino acids. For TMAH thermochemolysis, if phthalimide, N-methyl is selected as the representative molecule indicating the presence of phthalic acid in the parent sample prior to TMAH thermochemolysis, the response of this molecule gives the LOD for phthalic acid as 7.67 nmol and the LOQ is 23.25 nmol. Even though phthalic acid, N-methyl is not the most prominent peak in the chromatogram, it is easily distinguished as a product of phthalic acid. Dimethyl phthalate is the directly methylated product of phthalic acid in the TMAH chromatogram and its chromatographic peak is quantified relative to the quantity of moles of phthalic acid introduced to the TMAH thermochemolysis reaction ( Figure 69). For the 0.1 wt. % sample, dimethyl phthalate (from the TMAH thermochemolysis reaction) is below the limit of quantification. This represents a potential challenge to detection of some carboxylic and amino acids in samples after TMAH thermochemolysis, since the byproducts of the parent molecule will have higher limits of detection than for a molecule kept intact.However, this also shows the importance of generating chromatograms such as those in this section which give the suite of products produced after TMAH thermochemolysis with only one molecule doped on the parent sample. Known combinations of molecules may be used to collectively give an indication of the parent molecule or molecules.

IV.3.3.3. Mass spectra

A large number of byproducts can be produced and visible in a chromatogram due to the chemical reagents used for derivatization and thermochemolysis. Additionally, multiple distinct species can be produced from the derivatization of a single parent organic compound. The number of chromatographic peaks that arise from both of these phenomenon result in overlapping peaks, or coelutions, which can obscure mass spectrum of a given chromatographic peak and challenge a strict identification against known spectra. In addition to the suite of species which occur even in mixtures of chemical standards, the presence of a mineral matrix provides the possibility of additional species which can be produced during heating of the solid sample. The possibility of interference with the mass spectrum of derivatized organic molecules from the heating of the mineral matrix during derivatization and thermochemolysis is explored. Figure 70 shows mass spectra of montmorillonite doped with glutamic acid at 5 wt. % under each of the wet chemistry protocols compared with either the NIST spectrum, a chemical standard run in the lab, or a chemical standard spiked onto clean fused silica in the lab. Figure 70 also shows a comparison between mass spectra of montmorillonite doped with glutamic acid at 5 wt. % and 0.1 wt. % under MTBSTFA derivatization in order to compare the mass spectra results between samples at different concentrations.

A past study of TMAH thermochemolysis of JSC Mars-1 on a laboratory COTS GC-MS linked to an EGA/PY-3030D Frontier Lab pyrolyzer was conducted to optimize the temperature protocol of TMAH thermochemolysis and to characterize the chromatogram of a natural sample after TMAH thermochemolysis [START_REF] Morisson | TMAH Thermochemolysis of a Martian Regolith Simulant: Optimization of an Analytical Method for the Detection of Trace Organic Matter by the MOMA-Pyr-GC-MS Experiment Onboard the ExoMars-2020 Rover[END_REF]. A total of 47, 169 and 229 compounds were identified after thermochemolysis at 400˚C, 500˚C and 600˚C respectively, with the total number of compounds detected much higher than these values, in particular at 500˚C and 600˚C. At these temperatures, many compounds exit coeluted from the column which makes their identification difficult, some are not present in the reference database of mass spectra (NIST) and others are not a sufficiently important signal compared to the background noise to be identifiable. Results with natural samples commonly have many signals present, even in XIC, and many compounds which are difficult to definitively identify due to their coelutions with other peaks, absence from the NIST database, and the intensity of the signal not sufficiently above the noise levels. An example of this is shown in Figure 39 (Chapter III, Section III.3.3.2), and demonstrates how retention time becomes necessary to strictly identify a compound due to the obscured mass spectrum.

For the most part, mass spectra of samples at 5 wt. % concentration have a very close resemblance to the chemical standard both in mass peaks and mass peak ratios. For DMF-DMA, because the 5 wt. % samples produced chromatographic peaks that were very close to the instrument noise levels, there is less of a match to NIST for the Mont+Glu, 5 wt. % sample than for the chemical standard run at high concentrations. Therefore, these spectra show that breakdown of the mineral does not interfere via coeluting peaks at MTBSTFA and DMF-DMA derivatization temperatures (i.e., 140-250˚C) nor at TMAH thermochemolysis temperatures (i.e., 600˚C). While the mass spectrum of derivatized glutamic acid in the 5 wt. % sample is unobscured, the mass spectrum for the 0.1 wt. % sample would not produce a positive hit in the NIST database and could not be identified without a known retention time. However, this interference is primarily due, not to coeluting peaks caused by the breakdown of the mineral, but rather the noise background of the instrument or the noise produced by the presence of the chemical reagent (e.g. m/z 73 and m/z 147 noise wipes out the peaks for the mass spectrum of glutamic acid).

However, these samples include organic molecules which are not fully integrated into the mineral interlayers and it has not been explored how an added organic extraction step (e.g., thermodesorption on MOMA) may modify these results. Also, martian samples or natural martian analog samples have trace levels of organics, so mass spectra similar to the Mont+Glu, 0.1 wt. % sample are expected, and may produce many more chromatographic peaks due to the higher complexity of the sample in comparison to 1 mineral+1 organic compound samples. Since trace levels of organics are expected in relevant samples, the Mont+Glu, 0.1 wt. % case is also a good example of the importance of the coupling of the GC and MS in order to make strict identifications. Mass spectra are often not enough to make a positive identification due to the kind of interference shown here. Retention libraries (Chapter III) are critical for identification in these scenarios. To compare the difference in produced mass spectra between the chemical standard and the standard doped onto the mineral, it would be necessary to conduct a test in which the same quantity of organic compound is sent to the GC column with and without the presence of the mineral matrix.

IV.3.4. Pyrolysis and wet chemistry of samples with magnesium perchlorate Montmorillonite samples that were spiked at 5 wt. % and 1 wt. % organics and 1 wt. % Mgperchlorate (MontP+AMP, MontP+Glu, MontP+Phe, and MontP+PhA) were tested under ramp and flash pyrolysis (Section IV.3.1), MTBSTFA and DMF-DMA derivatization (Sections IV.3.2.2 and IV.3.2.3), and TMAH thermochemolysis (Section IV.3.2.4). This section will explore the effect of the presence of perchlorate on the GC-MS analysis.

IV.3.4.1. Pyrolysis in the presence of Mg-perchlorate

The contamination that was identified in the montmorillonite blank (Section IV.3.2.1) was also identified in the MontP blank. In addition, pyrolysis of MontP shows expected peaks of O2 and HCl from the decomposition of Mg-perchlorate. The pyrolysis tests on samples with and without perchlorate are qualitatively similar with at least three distinctions. First of all, there is the added presence of HCl in all runs. O2 peak is very weak in samples spiked with organics, compared to the MontP sample, because it is consumed for oxidation of organics. The 5 wt. % organics, in addition to the contamination intrinsic to the montmorillonite, exceeds the molar abundance of O2 released from the 1 wt. % Mg-perchlorate. However, the kinetics of oxidation and the constantly flushed injector allows the combustion not to be complete and O2 and organics residues to be observed. This is corroborated with the high abundance of CO2 observed in the GC-MS run. The HCl peaks are either a wide peak (in

HCl

Column bleed

HCl

MontP+AMP and MontP+Glu runs) or a broad background which appears throughout a large portion of the given run (MontP+Phe and MontP+PhA runs). This feature is not fully explained; however, the presence of water, solid matrix and molecules must play an important role in the distribution of HCl along the GC-MS run. Figure 72 compares Mont+AMP and MontP+AMP and shows the generation of O2 and HCl in the presence of Mg-perchlorate. The HCl peak in this run is an example of a sharp peak rather than a broad background. Acetonitrile and HCN abundances are not much different with or without perchlorate; just much higher amount of CO2 in sample without perchlorate. This is the opposite trend than expected, because more oxidation is observed in the presence of perchlorates. However, the pyrolysis happening in air, O2 is not quantifiable and is highly present in both runs with and without perchlorate. It is interesting to note that while the sample contamination is heavily present in the Mont+AMP sample, those compounds were not detected in the presence of perchlorate. This is explained by an excess of O2 released at high temperature when the Mg-perchlorate decomposes (200-500 °C), which then may be concomitant to the release temperature of the contamination and enhances its oxidation. 4) column bleed, ( 5) HCl. The GC column was held at 40˚C (7 minutes), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

In the case of the sample doped with phenylalanine in the presence of Mg-perchlorate, there is a formation of additional more oxidized compounds such as benzofuran, acetophenone, and dihydrobenzofuran (Figure 73) which are formed from the production of O2 from the degradation of Mg-perchlorate. No additional more oxidized compounds were observed in the sample doped with Mg-perchlorate and PhA, Glu and AMP compared to the same organics doped in a sample without perchlorate. However, the formation of chlorobenzenes (chlorobenzene, three isomers of dichlorobenzene and three isomers of trichlorobenzene) are observed in the presence of perchlorate in MontP+PhA (Figure 74) and a small amount of chlorobenzene in the MontP+Phe run. In the MontP+PhA run, the formation of benzoic acid and benzene is observed, as decarboxylation products of benzoic acid. The presence of all chlorinated, oxidized and decarboxylated forms of PhA means that numerous chemical reactions are at work during the pyrolysis in the presence of perchlorate, and the relative abundances of perchlorate to organics as well as the pyrolysis conditions (temperature, ramp, He flow rate etc.) are important parameters in this reaction. The large peak of benzeneethanamine (Figure 73) which is present in the Mont+Phe run and missing from the MontP+Phe run, and which may be the parent molecule of the chlorobenzene present in this run. 2) hydrogen cyanide, (3) acetonitrile, (4) benzene, (5) toluene, (6) ethylbenzene, dimethylbenzenes, (7) styrene, (8) ethylbenzenes, trimethylbenzenes, (9) propylbenzene, (10) benzene, 1-ethnyl-3methyl, (11) benzonitrile, ( 12) indane; benzene, 1-propynyl-; benzene, 3-pentenyl, (13) phenethylamine, ( 14) benzyl nitrile, (15) naphthalene, ( 16) benzenepropanitrile, (17) quinoline, (18) indole, ( 19) benzenebutanenitrile; quinoline, 3-methyl; biphenyl, indolizine, methyl, (20) diphenylmethane, (21) 1H-pyrrole, 2-phenyl; biphenyl, ethyl; (22) bibenzyl, (23) biphenyl, dimethyl; benzene, ethylbenzene; pentanone, methyl, diphenyl; (24) propane, diphenyl, (25) stilbene, (26) diphenylcyclopropane, (27) 1H-indene, 2-phenyl or anthracene, methyl, (28) 3-methyl-1-phenyl-1Hindene, ( 29) Benzeneethanamine, N-(phenylmethylene)-; 9H-Fluorene, 9-methylene-; 1H-indene, 1-(phenylmethylene)-, (30) 1H-indene, 2-phenyl or anthracene, methyl (31) naphthalene, 2-phenyl-, (32) 2,6diphenylpyridine, (33) chlorobenzene, (34) benzofuran, (35) acetophenone, (36) dihydrobenzofuran. GC column: 40˚C (hold for 7 minutes), ramp to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

Figure 74 shows a comparison between montmorillonite samples doped with Mg-perchlorate at 1 wt. % and phthalic acid at two different concentrations, 5 wt. % and 1 wt. %. In both cases, there is a production of chlorobenzene, dichlorobenzene (3 isomers), and trichlorobenzene (3 isomers) as well as chlorinated biphenyl. When phthalic acid is at 5 wt. %, there is an abundance of organic matter and, despite the production of chlorinated organics, there are prevalent peaks of phthalic acid and other products such as phenol and benzoic acid. However, when phthalic acid is at 1 wt. %, the phthalic acid is all consumed by the oxidation and chlorination reactions of organics and these peaks are not present in the chromatogram. The presence of chlorobenzenes in both cases confirms the kinetics competition between oxidation and chlorination of organics. It should also be noted that no O2 peak was detected in both GC-MS runs, suggesting in both cases it was all used to oxidize the organics. The presence of high quantity of residual organics (phthalic acid and other products) in the 5 wt. % run demonstrated that the organics were present at a higher molar ratio than O2 coming both from the perchlorate decomposition and the ambient atmosphere leaking (nominally) into the pyrolyzer. This provides insight on the initial ratio (> or < 1) between the Mgperchlorate and the organics molecules, and could be used on Mars to identify the relative abundance of organics to perchlorate salts. 3) column bleed, (4) chlorobenzene, ( 5) phenol, ( 6) three isomers of dichlorobenzene, ( 7) three isomers of trichlorobenzene, (8) benzoic acid, (9) phthalic acid, (10) biphenyl, ( 11) biphenyl, chloro-, (12) dibenzofuran, ( 13) benzophenone. TIC is in showed in black, and a reconstructed chromatogram with m112+m146+m180 is displayed in red. The GC column was held at 40˚C (7 minutes), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

IV.3.4.2. Derivatization in the presence of Mg-perchlorate

Direct MTBSTFA derivatization and solvent extraction coupled to MTBSTFA derivatization was performed on MontP+Glu, MontP+Phe, and MontP+PhA at 5 wt. % concentrations. Solvent extraction coupled to MTBSTFA derivatization was performed on the MontP+AMP, 5 wt. % sample. Direct DMF-DMA derivatization was performed on only one sample with perchlorate, MontP+Phe, 5 wt. % to confirm no substantial effect from the presence of Mg-perchlorate in contrast to the MTBSTFA results. Chromatograms were qualitatively identical in the TIC between runs with or without Mg-perchlorate for both derivatization techniques. Figure 75 shows an example of the similarity with the chromatograms of Mont+Glu samples at 5 wt. % with and without Mg-perchlorate after MTBSTFA derivatization in the presence of DMF. Figure 76 shows an example of the results that were obtained across the derivatization testing of samples with and without perchlorate, suggesting that Mg-perchlorate does not interfere with the analysis for MTBSTFA or DMF-DMA derivatization at these concentrations. There is possibly even a slightly higher response from derivatized organics in the presence of Mg-perchlorate. An extended study with perchlorate-containing samples across concentrations to see if a significant effect is observed could be undertaken with additional sample amounts from the same batch (Conclusions, Section IV.4).

Derivatization temperatures, 140˚C to 250˚C are much lower than pyrolysis (up to 830˚C) and thermochemolysis temperatures (600˚C) and are below the decomposition temperatures of perchlorate salts [START_REF] Sutter | Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune[END_REF]. Directed searches for chlorobenzene, dichlorobenzenes and trichlorobenzenes were performed using XIC. These compounds were searched for since they have been detected as reaction products of martian perchlorate and organic matter present in martian samples during GC-MS pyrolysis [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Szopa | First Detections of Dichlorobenzene Isomers and Trichloromethylpropane from Organic Matter Indigenous to Mars Mudstone in Gale Crater, Mars: Results from the Sample Analysis at Mars Instrument Onboard the Curiosity Rover[END_REF]. Very importantly, there are no chlorinated hydrocarbons, specifically these chlorobenzenes, observed in the derivatization runs with Mg-perchlorate in the tests presented here. While the derivatization reaction temperature is below the decomposition temperature of perchlorate salts, the salt could interfere with the chemical derivatization process itself by both physical and chemical interferences. Physical interferences include adsorption of derivatized organic compounds onto the salt, while chemical interferences can be even more problematic since the salt could interact with derivatization reagents, reducing the reaction yield and limiting the extraction yield, possibly to zero or below the instrument detection limit [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. This was demonstrated to be the case in a study of the Río Tinto sample in which hydrated salts (hydrated sulfates) in the sample were thought to contribute to a deactivation or reduction in the yield of the MTBSTFA reagent to the point of a non-detection of amino acid standards at known detectable concentrations in solution [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF]. This deactivation would be caused by the reaction of MTBSTFA with water or salts or any species capable of acting as a nucleophile in place of the amino and carboxyl groups of the amino acids.

Figure 76: Comparison of the chromatographic response between samples with and without Mg-perchlorate across solvent extraction+MTBSTFA derivatization, "direct" MTBSTFA derivatization, and "direct" DMF-DMA derivatization. The response from derivatized glutamic acid in the case of solvent extraction likely includes both derivatized pyroglutamic acid and glutamic acid. [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF] tested the influence of the presence of calcium sulfate salt (CaSO4) in solution at 0 to 700 g/L on the MTBSTFA derivatization of amino acids and nucleobases. They show that no physical or chemical interference takes place by the Ca 2+ or O4S -2 ions within the given concentration ranges, showing that the derivatization of organic compounds is possible even in the presence of sulfate salts [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. The derivatization results in this thesis section are consistent, demonstrating that the derivatization of organic compounds is possible even in the presence of perchlorate salts. In other words, the presence of perchlorate salts does not deactivate the MTBSTFA reaction or interfere with the reaction to the point of a non-detection of target compounds. However, because this part of the study is not quantitative, it is not possible to say if any deactivation of the derivatization reaction by the presence of perchlorate salt did occur. The slightly higher value of the organic chromatographic response across the tests suggests that interference from the salt would not interfere in the derivatization reaction to the point of a nondetection, although it is not quantified by these tests if an effect is significant.

An increased organic chromatographic response in the presence of perchlorate could be due to different catalytic effects of the mineral due to modified surface properties of the mineral in the presence of perchlorate or to differences in extraction efficiency due to the adsorption efficiency and locations on interlayers surfaces between the samples with and without perchlorate. Studies have indicated that the presence of dissolved salts in solid samples affects the sorption of organic compounds, specifically since salt ions can occupy interlayer spaces of montmorillonite and compete with organic molecules for available sites on inorganic surfaces (Villafañe- [START_REF] Villafañe-Barajas | Salinity Effects on the Adsorption of Nucleic Acid Compounds on Na-Montmorillonite: a Prebiotic Chemistry Experiment[END_REF]. The adsorption capacity can be affected by dissolved salts in thermodynamic terms as deduced by molecular dynamic models, which suggest that salts are absorbed in the interlamellar spaces of clay samples and can interact with oxygen atoms exposed on the edges of clay or inside its interlayers, reducing the sorption of the organic molecules (Villafañe- [START_REF] Villafañe-Barajas | Salinity Effects on the Adsorption of Nucleic Acid Compounds on Na-Montmorillonite: a Prebiotic Chemistry Experiment[END_REF]. If organic compounds experience a reduction in sorption to mineral surfaces, this might explain a putative increased response in our study due to a higher extraction efficiency.

IV.3.4.3. Thermochemolysis in the presence of Mg-perchlorate

Pure montmorillonite with and without perchlorate in the presence of TMAH produce qualitatively similar chromatograms. The majority of the compounds in both chromatograms come from the degradation of TMAH. Figure 77 shows a comparison of the montmorillonite sample doped with phenylalanine with and without perchlorate. The chromatograms are qualitatively similar with the exception of a few peaks such as chlorobenzene. Chlorobenzene is detected in both samples (Mont+Phe and MontP+Phe, both at 5 wt. %) but the estimated concentration is about 2•10 -11 mol/g (sample with perchlorate) against 6.6•10 -12 mol/g (sample without perchlorate). It is likely that the chlorobenzene in the sample without perchlorate is contamination from another test.

Chlorobenzene is produced from the reaction of Mg-perchlorate with organics during the TMAH thermochemolysis reaction since the thermochemolysis reaction occurs at 600˚C, higher than the derivatization reactions (140˚C to 250˚C) and above the decomposition temperature of perchlorate salts [START_REF] Sutter | Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune[END_REF]. The organic response (measured by peak area) is also higher in the case of the sample without perchlorate compared with the organic response in the case of the sample with Mg-perchlorate. For example, the ratio of the peak area of the directly methylated product of phenylalanine (L-phenylalanine, N,N-dimethyl-, methyl ester) to the peak area of the internal standard (D8-naphthalene) is higher in the test of the sample without perchlorate (A/AIS = 0.51) than in the test of the sample with perchlorate (A/AIS = 0.15). This result, together with the presence of chlorobenzene in the chromatogram, is consistent with a reaction of Mg-perchlorate with the spiked organics present in the sample.

IV.4. Conclusions

This chapter describes GC-MS analysis of montmorillonite samples spiked with four organic compounds. GC-MS analyses included pyrolysis-GC-MS, MTBSTFA and DMF-DMA derivatization GC-MS, and TMAH thermochemolysis GC-MS. 1) toluene, (2) 3-aminoisobutyric acid, (3) chlorobenzene, (4) ethylbenzene, ( 5) styrene, (6) Cumene, (7) Benzaldehyde, ( 8) Benzene, propenyl-, (9) Benzylnitrile, (10) Hydrocinnamic acid, methyl ester, (11) Cinnamic acid, methyl ester, ( 12) phenylalanine, N,N-dimethyl-, methyl ester, (13) Bibenzyl, ( 14) Propane 1,(15) Naphthalene, 2-phenyl, ( 16) Pyridine, 2,6-diphenyl. The GC column was held at 45˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.

1 mL•min -1 .
The following main conclusions and results which correspond to sections of this chapter are given below.

IV.a. Pyrolysis (Section IV.3.1) i. Pyrolysis products of the samples include the pure organic test compound (PhA), decarboxylation products (Glu, Phe, AMP, PhA), water/CO2 elimination (Glu), reactions leading to benzyl radicals (Phe), and possibly dimerization reactions (PhA) as well as high amounts of water and CO2. ii. There is a wide variation in number of pyrolysates from 2-3 (AMP) to over 30 (Phe) pyrolysates, due to differences in the adsorption of compounds to the mineral matrix, catalytic or stabilizing effects from the mineral matrix, or the thermal fragility of the compound. iii. Flash pyrolysis of PhA samples in the presence of perchlorate produce a greater number of pyrolysates than ramp pyrolysis.

IV.b. Derivatization (Sections IV. 3.2,IV.3.2.2,and IV.3.2.3) i. MTBSTFA derivatives of Glu, Phe, and PhA were detected at all three concentrations (5, 1, and 0.1 wt. %), while evidence of AMP was not detected at any concentration with MTBSTFA with solvent extraction or direct derivatization. ii. Glu, Phe, and PhA at the highest concentration, 5 wt. %, were harder to detect with DMF-DMA derivatization as the chromatographic response was close to the noise limit. This difficulty prompted variation of the derivatization temperature protocol for DMF-DMA (140˚C, 200˚C, 250˚C), which yielded an increasing chromatographic response with increasing temperature for all compounds (Glu, Phe, PhA). Evidence of AMP was not detected at a 5 wt. % concentration with DMF-DMA with solvent extraction or direct derivatization. iii. AMP or its derivatives were not detected with either MTBSTFA or DMF-DMA derivatization due either to a high molecular weight (did not elute from column or has too high of a RT), inefficient extraction of AMP from mineral, and/or partial deactivation of the derivatization reagent.

IV.c. TMAH thermochemolysis (Sections IV. 23).

IV.e. Presence of Mg-perchlorate in samples (Section IV.3.4) i. Additional oxygenated compounds were detected in pyrolysis of perchloratecontaining samples with Phe and some chlorohydrocarbons detected in the perchlorate-containing samples with PhA, although these signals did not interfere with detection of the organic molecules and/or their pyrolysates. ii. No chlorinated hydrocarbons observed in derivatization tests with or without perchlorate, due to the derivatization reaction, which is below the decomposition temperature of Mg-perchlorate (≤250˚C).

The following future studies and recommendations are proposed which correspond to the sections of this chapter are given below.

IV.R.a. Investigate non-detection of AMP-related derivatives through consideration of appropriate extraction solvent.

IV.R.b. Compare the difference in produced mass spectra between the chemical standard and the standard doped onto the mineral, by testing the same quantity of organic compound sent to the GC column with and without the presence of the mineral matrix.

IV.R.c. Since transformation of the crystal structure of montmorillonite has been observed between 500 and 1000˚C [START_REF] Grim | Clay Mineralogy[END_REF][START_REF] Xie | Thermal Degradation Chemistry of Alkyl Quaternary Ammonium Montmorillonite[END_REF], it would be interesting to perform XRD and/or XRF analysis of the samples post-thermochemolysis to see if there are differences in the mineral phases or mineral chemical composition of the samples.

These types of laboratory analyses will be important analog GC runs during MOMA operations on Mars in order to (1) predict and identify compounds of interest, including degradation and reaction products, in flight chromatograms, and (2) learn more about the martian parent mineral based on identified compounds in the chromatogram and in comparison, to these types of analog samples. For more realistic studies, natural/more complex samples are needed and this will be explored in the following perspectives chapter, Chapter V.

Chapter V: Perspectives on the development and testing of space-like laboratory-based experimental setups for derivatization-GC-MS of natural samples

Summary

Previous chapters of this thesis (Chapters III-IV) explore the testing of relatively straight-forward samples (chemical standards, mineral samples with a single spiked organic compound) using mostly COTS laboratory GC-MS setups. However, there are specific complexities to natural samples (e.g., suites of indigenous species, trace quantities of organics) and to space experimentation (e.g., complex gas processing systems, adsorption/desorption trapping) that may present unique challenges for strict detection of target compounds such as amino acids. This chapter is a perspectives chapter which explores the demonstrated detections of amino acids using MTBSTFA derivatization through a review from the literature of demonstrated detections of amino acids using MTBSTFA derivatization, with focused attention on the complexity of the sample under testing and to the fidelity of the experimental setup to space-like experimentation on SAM and MOMA. Laboratory experimental setups for derivatization testing of natural samples are explored, with examples from preliminary results and a discussion of the pros and cons of each setup for its applicability and usefulness to the implementation of the space experiment.

Perspectives for future laboratory testing of flight-like derivatization and thermodesorption testing of natural samples are also presented.

V.1.

State of the art

As introduced in Chapter I (Section I.3.2.3), MOMA will carry two derivatization reagents, MTBSTFA/DMF and DMF-DMA, and a thermochemolysis reagent, TMAH, in order to enable the detection of volatile molecules such as carboxylic and amino acids. The following section will expand on this introduction of MTBSTFA for flight derivatization experiments by discussing the state of the art of demonstrated detections of amino acids in the laboratory using MTBSTFA derivatization and their applicability to the space experiment, with a focus on two important components for detection of amino acids in martian samples: (1) the extraction of amino acids from the mineral matrix of a natural sample, and therefore, availability for derivatization by MTBSTFA, and (2) the laboratory experimental setup, its fidelity to flight instrumentation, and the corresponding implications for the detection of amino acids with the space experiment in comparison to the laboratory.

V.1.1.

MTBSTFA derivatization with amino acid chemical standards

In the case of very fragile (easily degradable by pyrolysis) or refractory molecules, which cannot be analyzed by heating, a spaceflight-compatible chemical derivatization reaction has been performed (SAM) or will be performed (MOMA) on Mars. Chemical derivatization of both amino and carboxylic acids is achieved by the MTBSTFA silylation reaction in order to transform nonvolatile species into volatile species for better detection by GC-MS and to depolarize the polar function of volatile molecules, since polar functions often have poor interactions with the stationary phase of the GC column (Figure 17). Advantages of MTBSTFA derivatization include that it is a single-step reaction [START_REF] Knapp | Handbook of Analytical Derivatization Reactions[END_REF], it is less susceptible to hydrolysis compared to other reagents, and it does not require separation of the derivatives prior to GC analysis. In comparison to other silylating reagents such as 1-(tert-Butyldimethylsilyl)imidazole (tBDMSIM) and tertbutyldimethylchlorosilane (tBDMCS), MTBSTFA has enhanced reactivity, including its ability to silylate carboxyls, hydroxyls, thiols and primary and secondary amines, in addition to short reaction times, even at room temperature, and simplified work since the derivatization byproduct is neutral and volatile [START_REF] Woo | Capillary gas chromatographic determination of proteins and biological amino acids as N(O)-tert.-butyldimethylsilyl derivatives[END_REF]. MTBSTFA is also sensitive to a wide range of organic compounds with acidic hydrogen atoms, including amino acids, carboxylic acids, nucleobases, primary and secondary amines, alcohols, and amides.

For amino acids, MTBTFA has been shown to have yields in the range of 90-100% with amino acid chemical standards [START_REF] Rodier | Detection of martian amino acids by chemical derivatization coupled to gas chromatography: In situ and laboratory analysis[END_REF] MTBSTFA can be used by itself; however, adding a solvent and proton acceptor increases the reaction yield considerably [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]). As such, dimethylformamide (DMF) is often used in the laboratory and in space experiments as a solvent to MTBSTFA. DMF is present in the SAM derivatization capsules, which contain 0.5 mL of a 4:1 mixture of MTBSTFA and DMF [START_REF] Mahaffy | The Sample Analysis at Mars Investigation and Instrument Suite[END_REF]. A challenge of DMF is that it is hydrophilic and will contain water in solution. The presence of water poses a challenge for MTBSTFA derivatization due to a preferential reaction of MTBSTFA with water to produce both mono-and bisilylated water compounds that can produce sizable background signals [START_REF] Leshin | Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover[END_REF]) and compete with derivatization of the compounds of interest such as amino acids.

Since the 1980s, the silylating reagent MTBSTFA has been successfully adopted for derivatization into tBDMS derivatives for amino acids by a one-step reaction and studies demonstrated the production and detection of stable, single amino acid derivatives [START_REF] Mackenzie | Gas-liquid chromatographic assay for asparagine and glutamine[END_REF][START_REF] Mackenzie | Analysis of amino acids by gas-liquid chromatography as tert.-butyldimethylsilyl derivatives. Preparation of derivatives in a single reaction[END_REF][START_REF] Biermann | Analysis of amino acids as tert.-butyldimethylsilyl derivatives by gas chromatography[END_REF][START_REF] Mawhinney | N-Methyl-N-(tertbutyldimethylsilyl)trifluoroacetamide and related N-tert-butyldimethylsilyl amides as protective silyl donors[END_REF][START_REF] Goh | Analysis of all protein amino acids as their tert.-butyldimethylsilyl derivatives by gas-liquid chromatography[END_REF][START_REF] Das Neves | Capillary gas chromatography of amino acids, including asparagine and glutamine: sensitive gas chromatographic-mass spectrometric and selected ion monitoring gas chromatographic-mass spectrometric detection of the N,O(S)-tert.-butyldimethylsilyl derivatives[END_REF][START_REF] Das Neves | Capillary gas chromatography of amino acids as their tert-butyldimethylsilyl derivatives in the analysis of serum amino acids in metabolic diseases[END_REF]. Some of the properties of these tBDMS amino acid derivatives were advantageous with respect to inertness, separation, thermal and hydrolytic stability, sensitivity, and selectivity and the possibility to apply direct injection [START_REF] Woo | Capillary gas chromatographic determination of proteins and biological amino acids as N(O)-tert.-butyldimethylsilyl derivatives[END_REF]. However, the specific experimental parameters and reaction protocol can have implications on the detectability of amino acids using MTBSTFA derivatization-GC-MS. For example, proposed reaction temperatures in the literature vary between 50-150˚C and derivatization times between 25 and 150 min. There is also variability in the number of tBDMS amino acid derivatives reported, with some papers reporting double derivatives (e.g., [START_REF] Goh | Analysis of all protein amino acids as their tert.-butyldimethylsilyl derivatives by gas-liquid chromatography[END_REF][START_REF] Mackenzie | Gas-liquid chromatographic assay for asparagine and glutamine[END_REF][START_REF] Mackenzie | Analysis of amino acids by gas-liquid chromatography as tert.-butyldimethylsilyl derivatives. Preparation of derivatives in a single reaction[END_REF], while others report no double derivatives [START_REF] Molnár-Perl | GC-MS of amino acids as their trimethylsilyl/tbutyldimethylsilyl Derivatives: In model solutions III[END_REF]. There are also other reports that not all of the 22 protein amino acids were derivatized into tBDMS derivatives [START_REF] Biermann | Analysis of amino acids as tert.-butyldimethylsilyl derivatives by gas chromatography[END_REF][START_REF] Early | Capillary gas chromatographic analysis of amino acids in blood and protein hydrolysates as tert.-butyldimethylsilyl derivatives[END_REF]. Substantial amounts of glutamine, asparagine and tryptophan were shown to be destroyed during derivatization [START_REF] Biermann | Analysis of amino acids as tert.-butyldimethylsilyl derivatives by gas chromatography[END_REF][START_REF] Early | Capillary gas chromatographic analysis of amino acids in blood and protein hydrolysates as tert.-butyldimethylsilyl derivatives[END_REF]) and derivatization of threonine was very difficult [START_REF] Mawhinney | Analysis of Amino Acids as Their tert-Butyldimethylsilyl Derivatives by Gas-Liquid Chromatography and Mass Spectrometry[END_REF]). Finally, basic amino acids (arginine, histidine, lysine) are the most difficult to derivatize, and require additional reaction time in order to achieve maximum derivatization yield [START_REF] Das Neves | Capillary gas chromatography of amino acids, including asparagine and glutamine: sensitive gas chromatographic-mass spectrometric and selected ion monitoring gas chromatographic-mass spectrometric detection of the N,O(S)-tert.-butyldimethylsilyl derivatives[END_REF]). Arginine appears to be the most difficult amino acid to fully derivatize [START_REF] Das Neves | Capillary gas chromatography of amino acids, including asparagine and glutamine: sensitive gas chromatographic-mass spectrometric and selected ion monitoring gas chromatographic-mass spectrometric detection of the N,O(S)-tert.-butyldimethylsilyl derivatives[END_REF], that is, the amino acid for which derivatization of all its available labile hydrogens is the most difficult to obtain. The pattern of arginine fragmentation is also difficult to predict. Histidine, for example, has a betaimidazole group and it has been shown that the silylated imidazole compounds are themselves excellent donors of the silyl function [START_REF] Mawhinney | Analysis of Amino Acids as Their tert-Butyldimethylsilyl Derivatives by Gas-Liquid Chromatography and Mass Spectrometry[END_REF]. Histidine is therefore probably easily subject to the desilylation of its silylated imidazole group, thus limiting its detection by GC-MS [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF]. These nuances illustrate the variability in efficiency of the derivatization reaction that can occur even when applied to chemical standards and applied to different compounds within a chemical family.

V.1.2.

MTBSTFA derivatization aided by extraction

Successful detection of amino acids in martian samples, or other solid samples, requires efficient derivatization of the amino acid molecule and efficient extraction of the molecule from the mineral matrix so that it can be derivatized and then detected by GC-MS. Studies of MTBSTFA derivatization GC-MS for the application of the analysis of planetary regolith samples vary in the (1) complexity of the sample under testing, which will be discussed in this section, and (2) the experimental fidelity to the flight space experiment (Figure 78), which will be discussed in the following section. In addition to the substantial testing on chemical standards, MTBSTFA derivatization has been utilized for the determination of amino acids in natural samples, mostly through the use of extraction techniques and the subsequent analysis of extracts by derivatization-GC-MS. For example, MTBSTFA has been used extensively for applications in the medical field for the analysis of amino acids in samples of human blood, plasma, serums, protein hydrolysates, and urine samples [START_REF] Berger | Trace element supplementation after major burns increases burned skin trace element concentrations and modulates local protein metabolism but not whole-body substrate metabolism[END_REF][START_REF] Calder | Quantitation of blood and plasma amino acids using isotope dilution electron impact gas chromatography/mass spectrometry with U-(13)C amino acids as internal standards[END_REF][START_REF] Deng | Development of microwave-assisted derivatization followed by gas chromatography/mass spectrometry for fast determination of amino acids in neonatal blood samples[END_REF][START_REF] Early | Capillary gas chromatographic analysis of amino acids in blood and protein hydrolysates as tert.-butyldimethylsilyl derivatives[END_REF][START_REF] Mcgaw | Comparison of orthogonal liquid and gas chromatography-mass spectrometry platforms for the determination of amino acid concentrations in human plasma[END_REF][START_REF] Shoemaker | Automated screening of urine samples for carbohydrates, organic and amino acids after treatment with urease[END_REF], and rodent samples [START_REF] Wood | Neurochemical analysis of amino acids, polyamines and carboxylic acids: GC-MS quantitation of tBDMS derivatives using ammonia positive chemical ionization[END_REF] as well as for the analysis of amino acids in food products, including potato juice extracts [START_REF] Davids | Use of unusual storage temperatures to improve the amino acid profile of potatoes for novel flavoring applications[END_REF][START_REF] Starke | Separation, identification, and quantification of amino acids in L-lysine fermentation potato juices by gas chromatography-mass spectrometry[END_REF], meat samples [START_REF] Pérez-Palacios | A Rapid and Accurate Extraction Procedure for Analysing Free Amino Acids in Meat Samples by GC-MS[END_REF], tea extract [START_REF] Zhang | Determination of Main Free Amino Acids in Tea by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID)[END_REF]) and grape juice extracts for the application of improving the taste of wine [START_REF] Hannam | Amino Acid Composition of Grape (<em>Vitis vinifera</em> L.) Juice in Response to Applications of Urea to the Soil or Foliage[END_REF]. MTBSTFA derivatization has been coupled to GC-MS and GC gas isotope ratio mass spectrometry (G-IRMS) for the analysis of amino acids in soil and plant extracts, including leaf and nodule total organic matter (TOM) extracts [START_REF] Molero | Measurement of 13C and 15N isotope labeling by gas chromatography/combustion/isotope ratio mass spectrometry to study amino acid fluxes in a plant-microbe symbiotic association[END_REF], root extracts [START_REF] Persson | A GC-MS method for determination of amino acid uptake by plants[END_REF], soil cores and soil extracts [START_REF] Bol | Long term changes in the distribution and delta N-15 values of individual soil amino acids in the absence of plant and fertiliser inputs[END_REF][START_REF] Williams | Characterization of the water soluble soil organic pool following the rewetting of dry soil in a drought-prone tallgrass prairie[END_REF], and plant tissue extracts [START_REF] Lesuffleur | Root amino acid exudation: measurement of high efflux rates of glycine and serine from six different plant species[END_REF] as well as for the study of herbicides [START_REF] Moye | A simple single-step derivatization method for the gas chromatographic analysis of the herbicide glyphosate and its metabolite[END_REF][START_REF] Tsunoda | Simultaneous determination of the herbicides glyphosate, glufosinate and bialaphos and their metabolites by capillary gas chromatography-ion-trap mass spectrometry[END_REF]. Additionally, MTBSTFA derivatization and GC-MS has been used to analyze amino acids present in the drying oils and proteinaceous binders in samples from painted artworks [START_REF] Colombini | Characterisation of proteinaceous binders and drying oils in wall painting samples by gas chromatographymass spectrometry[END_REF], in aerosols [START_REF] Mandalakis | Trace analysis of free and combined amino acids in atmospheric aerosols by gas chromatography-mass spectrometry[END_REF] and in E. coli samples [START_REF] Sobolevsky | Comparison of silylation and esterification/acylation procedures in GC-MS analysis of amino acids[END_REF].

However, this existing literature outside the planetary community covers mostly the analysis of chemical standards or extracts from natural samples. There is not literature covering the analysis of regolith samples in which the derivatization reagent is applied directly to the soil sample as is the case in the space experiments or in the laboratory experiments that are described in this chapter.

Various studies have tested the effect of parameters (e.g., pH of the sample, exposure to gamma radiation) on the efficiency of the MTBSTFA derivatization reaction using amino acid chemical standards (e.g., [START_REF] Belmahdi | Extraterrestrial material analysis: influence of the acid hydrolysison the mtbstfa derivatization[END_REF]Freissinet et al. 2019). Several studies have also explored the MTBSTFA derivatization of mineral samples or natural samples which have been spiked with organics. For example, studies have focused on the effect of the mineral matrix on the derivatization reaction itself [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF] as well as the extraction efficiency of solvent extraction aided by sonification for the extraction of amino and carboxylic acids [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF][START_REF] Buch | Solvent extraction of organic molecules of exobiological interest for in situ analysis of the Martian soil[END_REF]. [START_REF] Morisson | TMAH Thermochemolysis of a Martian Regolith Simulant: Optimization of an Analytical Method for the Detection of Trace Organic Matter by the MOMA-Pyr-GC-MS Experiment Onboard the ExoMars-2020 Rover[END_REF] detected derivatized amino acids, including derivatized valine, leucine, isoleucine, proline, 5-oxo-proline, and phenylalanine, from a natural solid sample, JSC Mars-1, using solvent extraction prior to MTBSTFA derivatization and injection to a COTS GC-MS. All of these studies presented in this paragraph are performed with the MTBSTFA derivatization at 75˚C for 15 to 30 minutes. For MOMA, derivatization is performed at higher temperatures, e.g., ~250˚C, [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]) in order to aid in the desorption of target compounds from the mineral matrix. MTBSTFA derivatization on SAM can be performed at a chosen temperature and can be performed either hot or cold. As presented and discussed in Chapter IV (Section IV.3.2.1), the derivatization temperature and duration have an effect on the background of derivatization products as well as the efficiency of the derivatization reaction. Additionally, when a mineral matrix is present, solvent extraction is used to extract amino acids and other target compounds from the matrix. However, solvent extraction, which is the extraction technique used in the experiments described above, is not a capability of flight experiments. Flight derivatization is performed online as a one-pot/one-step extraction and derivatization protocol.

Some laboratory tests have studied (1) the effect of higher derivatization temperatures on the MTBSTFA background and the derivatization efficiency of target molecules at these higher temperatures as well as (2) the efficiency of thermodesorption as an extraction technique, particularly when combined in a one-pot/one-step protocol. For example, David et al. (2016) shows the influence of a mineral matrix to inhibit the detection of amino acids at different temperatures. The recovery of amino acid derivatives decreased when MTBSTFA derivatization was performed at higher temperatures (i.e., 300˚C) possibly due to incomplete silylation of trisubstituted amino acids (e.g., serine), the release of water from the mineral, enhancement of catalytic effects of the matrix, and low thermal stability of amino acids when submitted to temperatures higher than 200˚C (since these amino acids were spiked onto the mineral). Detection of amino acid derivatives also failed when derivatization was performed on the Atacama sample. This result was attributed to the iron composition of Atacama samples that could inhibit the reaction [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF], since additional tests on 1% ferric or ferrous (Fe 3+ , Fe 2+ ) silica samples resulted in a total inhibition across the tested protocols (David et al. 2016). Derivatization on iron (Fe) rich samples occurred as well but with an additional average 10% loss in recovery of the overall amino acids (David et al. 2016). The efficiency of the thermodesorption as an extraction technique has also been studied; for example, a 1-pot/1-step extraction/derivatization online derivatization setup [START_REF] Meunier | A laboratory pilot for in situ analysis of refractory organic matter in Martian soil by gas chromatography-mass spectrometry[END_REF]) enabled the detection of Ala, Gly, and Val indigenous to a sample from the Atacama desert using a thermodesorption step at 500˚C for 5 minutes followed by the online derivatization [START_REF] Buch | Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results[END_REF]. For MOMA, this protocol is not compatible, since any pre-derivatization thermodesorption step will be performed below 221˚C, the eutectic opening temperature of the MTBTSFA capsule.

The effectiveness of the one-pot/one-step MTBSTFA extraction and derivatization protocol is an important question for space experiments utilizing this method of wet chemistry. In addition to the experiments described in the previous paragraph, there have been studies which utilize MTBSTFA derivatization of natural samples with one-pot/one-step MTBSTFA extraction and derivatization protocol within the adjustability of SAM. MTBSTFA derivatization experiments with SAM-like laboratory experimental setups have been studied by [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF] and [START_REF] Bishop | Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA[END_REF]. [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF] tested a variety of terrestrial martian analog materials using a SAM-like online setup (sample reactor oven, gas transfer line, hydrocarbon trap assembly) in which onepot/one-step extraction and derivatization could be performed at 300˚C for several minutes. Of the samples tested, two carboxylic acids were detected in an Atacama surface sample while proline and leucine were detected in a carbonate-rich stromatolite sample from Svalbard. No derivatized organics were detected in the other martian analog samples (JSC Mars-1, Río Tinto, Murchison, and an Atacama subsurface sample) using this technique. SAM-like derivatization experiments on Lake Hoare samples were conducted by [START_REF] Bishop | Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA[END_REF] using a SAM flight-like configuration with a one-pot/one-step extraction and derivatization protocol performed at 300˚C for 3 minutes.

Of the four Lake Hoare samples which were tested with this protocol, alanine and proline were each detected once in two different samples at low concentrations.

There have been limited MOMA-like derivatization studies performed. [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF] performed MTBSTFA derivatization on natural samples collected during the Arctic Mars Analog Svalbard Expedition (AMASE) to Svalbard, Norway. "Direct" derivatization was performed on samples in situ during the campaign to mimic a one-pot/one-step online scenario, in which MTBSTFA/DMF was added directly to ~10-20 mg of sample and derivatized at 175˚C for 10 minutes offline before syringe injection to the GC. No amino acid identifications from this protocol were presented. Complimentary laboratory derivatization experiments were also performed in the laboratory using the more conventional laboratory techniques of solvent extraction prior to offline derivatization, which allowed identification of Ala, Gly and Pro in the Botniahalvøya (AM11-162) sample. To date, there have been no experiments which demonstrate the detection of amino acids using an experimental setup with wet chemistry protocol within the adjustability of MOMA. For example, in Chapter III, MOMA flight spare columns were used to predict the retention times of a suite of target compounds in order to determine if these compounds were detectable under MOMA GC conditions such as a given flow rate, GC column temperature program and run time.

Even if the flight spare columns can be considered identical to those columns on the flight model and can be expected to be an accurate analog to the flight model hardware, the setup does not allow for other parameters which may affect the detectability of given target compounds, such as the ability of higher molecule weight compounds to pass through the adsorption/thermal desorption traps used for injection to the GC column. Figure 78 shows categories of increasing complexity of the sample under testing as well as increasing or varying fidelity of the experimental setup to a flight experiment. The complexity of the sample may not always be linked to the fidelity of the laboratory setup. For example, a discussion of the testing of natural samples using a COTS GC-MS for the application of offline direct derivatization is discussed in Section V.3.1.

Two important instrument components are the GC columns and the adsorption/thermal desorption traps. In preparation for specific space experiments, [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF] and [START_REF] Guzman | Testing the capabilities of the Mars Organic Molecule Analyser (MOMA) chromatographic columns for the separation of organic compounds on Mars[END_REF] tested MTBSTFA-derivatized amino acids (and other chemical families) using COTS GC-MS systems with SAM and MOMA (respectively) flight spare GC columns installed and with helium velocity and column temperature programs which mimicked the flight experiments. The study for MOMA is presented in this thesis in Chapter III. [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF] additionally performed tests on a COTS GC-MS system with a spare SAM GC column and a spare SAM injection trap (IT) installed between the split/splitless injector and the GC column. Although amino acids were not included in the chemical standards under testing, the study demonstrated the limitations of demonstrated detections on COTS systems which do not consider flight components such as the ITs, since in this study organics of medium molecular weight (bearing at least 4 carbon atoms) required multiple IT flashes to fully desorb the molecule, while for a heavier molecule, naphthalene, no release was observed from the IT after 8 successive IT activations.

Another important component of laboratory testing is how the derivatization is performed, both in terms of hardware (offline vs. online) and in protocol (T, t). Offline derivatization involves direct application of the derivatization reagent on the soil, prior to derivatization on a benchtop oven independent of the GC-MS instrument. A small portion of the derivatized sample is then injected to the GC-MS by microliter liquid syringe. The online one-pot/one-step extraction and derivatization protocol of space experiments involves custom laboratory setups which involve a derivatization oven or reactor that allows direct distribution of derivatized compounds, such as amino acids, to a trapping system or to the GC column. These two types of derivatization laboratory setups are further discussed in the results (Section V.3) and perspectives (Section V.4) parts of this chapter.

V.1.4. Adjustability of one-step/one-pot protocol for MOMA As discussed in the previous section, limited tests which mimic the SAM derivatization experiment have been performed on natural samples and have demonstrated detection of one or two amino acids [START_REF] Bishop | Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA[END_REF][START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF]. Detection of amino acids using MTBSTFA derivatization GC-MS have not been demonstrated in laboratory conditions which are compatible with the MOMA space experiment. This section will discuss the adjustability of the MOMA derivatization experiment. Experimental set-ups that aim to optimize the one-step/one-pot protocol should be able to test across this adjustability. The MOMA flight conditions for derivatization-GC-MS are also given in Chapter III (Table 8).

MOMA carries derivatization ovens of a diameter of 6 mm and an inner volume of slightly more than 200 mm 3 . One aliquot of powderized martian drill sample from the jaw crusher and dosing station is expected to have a volume of 100 mm 3 and may correspond to an approximate mass of 100 mg (assuming a bulk density of 1 g/cm 3 ). Each chemical reagent has been sealed into a stainless-steel capsule. The capsule has the following dimensions: external u = 3.2 mm, h = 4.3 mm, with an internal volume of about 25 µL. Because each reagent has to be released at a specific temperature, three different eutectic alloys have been implemented to seal the capsule up to a minimal temperature reached by the oven. The MOMA capsule containing MTBSTFA will release MTBSTFA at 221°C. About 15 µL of each reagent is stored in each capsule [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. The nominal implementation of the MTBSTFA derivatization experiment is to derivatize around 250˚C for up to 10 minutes [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]. It is possible to implement a separate drying step and/or a thermosdesorption step prior to the derivatization, as long as these conditions do not exceed the temperature of the eutectic of the capsules. A drying step would eliminate water from the sample, which can interfere with the derivatization reaction by preferentially reacting with MTBSTFA. The thermodesorption step will aid in thermally desorbing compounds of interest from the mineral matrix of the sample.

Within these constraints, Figure 79 shows a basic example of the temperature curve under which a sample may be heated during the thermodesorption-derivatization protocol. The thermodesorption temperature and duration (T, t) and the derivatization temperature and duration (T, t) are then the parameters which remain be optimized using natural samples in order to procure the optimal response from target compounds such as amino acids.

In the following section, potential laboratory experimental setups and methods are presented for performing derivatization that can mimic the wet chemistry performed on MOMA to varying degrees.

The following two types of laboratory setups are presented and discussed.

(1) Offline direct derivatization in which the quantity of derivatization reagent is applied directly to the sample and undergoes derivatization on a benchtop oven. A portion of the sample is injected to a COTS GC-MS by hand-held microliter-volume syringe. (2) Online derivatization performed in a homemade mini reactor which is inserted along the gas flow pathway. Valve switching allows for the derivatization to be performed within the V.2.2. Reactor online derivatization A system was constructed which couples a COTS GC-MS to a homemade reactor which enables both online thermodesorption and derivatization at relevant MOMA temperatures and adsorption/thermal desorption injection trapping. This system utilizes a homemade reactor that has been used in laboratory experiments previously [START_REF] Buch | Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results[END_REF][START_REF] Meunier | A laboratory pilot for in situ analysis of refractory organic matter in Martian soil by gas chromatography-mass spectrometry[END_REF]).

V.2.2.1. Samples

A solution of 2-methylnonane, decane and undecane, in cyclohexane at a concentration of 9.7 × 10 -5 , 9.0 × 10 -5 and 6.6 × 10 -5 M respectively, was used for the calibration of peak area on the reactor setup (99 %, Sigma-Aldrich for all compounds). JSC Mars-1, a martian regolith simulant, was used for the testing of solid samples in the reactor bed [START_REF] Allen | Martian Regolith Simulant JSC Mars-1[END_REF]).

V.2.2.2. Homemade laboratory setup coupled to COTS GC-MS for online derivatization

A homemade system was constructed for online derivatization which could be coupled to a COTS GC-MS. This homemade system includes a small reactor [START_REF] Meunier | A laboratory pilot for in situ analysis of refractory organic matter in Martian soil by gas chromatography-mass spectrometry[END_REF]) used for online derivatization connected to an GL Sciences Optic 4 GC Inlet via a Valco 6-port gas valve. The Optic 4 is used as either a conventional GC injector (on which syringe injection can be made directly) or as an adsorption/thermal desorption injector in which it undergoes a freeze (0˚C or below) in order to perform trapping of volatiles released from samples. In some tests, 30 mg of Tenax TA were added to the liner of the Optic 4 injector to aid trapping. There are two important transfer lines in the setup which are both heated by auxiliary sources: the transfer line between the reactor and the 6-port valve and the transfer line between the 6-port valve and the Optic 4. Transfer lines connect each of the elements and are heated to about 100˚C, which was not yet optimized. For example, MOMA transfer lines are heated to 130˚C. 100˚C is low for the efficient transfer of semi-volatiles such as derivatized amino acids and can impact the experimental results discussed in Section V.3.2. Details of the system are shown in Figure 81.

Samples can be introduced to the reactor bed in two ways: (1) through a syringe injection through the liquid inlet which is shown in Figure 82 and is fitted with a custom-cut miniature septum, and

(2) by deposition inside the 1.5 mL reactor chamber. The chemical standards which are discussed in Section V.4.2.1 were injected by method (1). The solid sample which is analyzed and discussed in Section V.3.2 was introduced to the reactor bed by method (2). For this test with a solid sample (JSC Mars-1), 41.1 mg of JSC Mars-1 was derivatized online in the reactor bed at 210˚C for 5 minutes. 3 µL MTBSTFA/DMF (4:1) was added by a 5 µL SGE syringe via method (1). Prior to the injection of the derivatization reagent, the sample was inside the reactor as it was heated from room temperature to 210˚C in 20 minutes (~9.5˚C/min).

The GC-MS measurements were carried out with a GC Trace Ultra coupled to a Single Quadrupole MS (DSQ II) (all from ThermoFisher Scientific). The GC column was a 30 m Zebron ZB-5MSplus (30 m x 0.25 mm x 0.25 µm). The column had an initial temperature of 40˚C and was ramped directly to 300˚C at 6˚C•min -1 . The flow rate was 1 mL•min -1 . The mass scan range was m/z 25 to 500.

Offline direct derivatization

The offline derivatization protocol is first described in Chapter III (Section III.2.1.4) and Chapter IV (Section IV.2). These tests were performed on natural samples (field sample or cleaned mineral matrix) that were spiked with organic compounds. In the offline direct derivatization protocol, a small amount of derivatization reagent (~10-15 µL) can be applied to small sample sizes on the order of tens of milligrams [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF]). However, a detection of amino acids from natural samples using this technique has not been demonstrated yet within the adjustability of the MOMA experiment. With the aim to demonstrate the detection of amino acids in a natural sample within the adjustability of MOMA, a direct derivatization experiment was performed on the ASAP Atacama Surface sample, after which directed searches for amino acids were performed. A solvent extraction protocol aided by sonification was also employed as a control, since it is a common and efficient extraction method and has been tested for amino acids using other Atacama samples [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. Figure 80 shows the process of performing a more traditional solvent extraction and offline derivatization protocol on a sample versus performing the offline direct derivatization protocol on the sample. No amino acids were detected using either technique (Figure 83) under the selected extraction and derivatization protocols. The MTBSTFA tests in Figure 83 were conducted on a chiral column, which is not nominal for MTBSTFA since the reagent does not enable detection of chiral enantiomers and a chiral column limits the maximum temperature of the column heating ramp. The solvent extraction test was repeated using a 30 m Zebron 5MSplus column (Section V.2.1.3) and amino acids were also not identified after a directed search in the XIC under these conditions. The peaks shown in the chromatogram of Figure 83 include expected peaks from the presence of MTBSTFA at higher temperatures, including boric acid, 3tBDMS and bis(tert-butyldimethylsilyl-2,2,2-trifluoro-Nmethylacetamide, but also include unknown byproducts which are currently under investigation. The expected differences between the solvent extraction and thermodesorption protocol are also not systematically tested and are specifically discussed as important work to be done in continuing to understand if amino acids can be reliably detected from natural samples using this direct derivatization protocol, and so be used for optimization studies for space experiments.

Directed searches for amino acids, aided by known retention times with chemical standards under the same test parameters, did not reveal identifications of any of the amino acids known to be present in the sample. The following calculations attempt to understand this non-detection in the context of known information about detection limits. For example, the most abundant amino acid, (Top) 15 µL of an isopropanol and H2O solution (1:1) are applied directly on 6.29 mg of the sample and it is placed in an ultrasonic bath at a frequency of 38 kHz set at 60˚C for 1 h [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. The solution was then left to evaporate under N2 flow for 30 min. Next, 10 µL of MTBSTFA/DMF (3:1) was added to the dried extract and underwent derivatization at 75˚C for 15 min. (Bottom) 6.02 mg of sample was sealed in a 5 mL ampule and was heated at 200˚C for 5 minutes. Next the sample was transferred to another 5 mL ampule and 9 µL of MTBSTFA/DMF (3:1) was added directly to the sample prior to undergoing derivatization at 170˚C for 10 minutes. 0.40 mg of sample was lost during the transfer of the sample from the thermodesorption step to the derivatization step. For the direct derivatization, 9 μL of MTBSTFA/DMF (3:1) was applied directly to about 6 mg of sample and sealed in a glass ampule. The sample was heated at 250 C for 3 min to allow the derivatization reaction to occur. In both tests, the derivatization was followed by GC-MS injection of 1 µL by hand-held 1 μL syringe (SGE). The GC column was an Agilent Chirasil Dex (30 m x 0.25 mm x 0.25 µm). The column had an initial temperature of 50˚C and a ramp to 190˚ at a rate of 3˚C•min -1 (Chirasil Dex). The flow rate was 1.0 mL•min -1 . The split ratio was 10:1 and the injection temperature was 280˚C. The mass scan range was m/z 10 to 550.

Given the protocols employed with the offline direct derivatization method, and assuming a sample size of 20 mg, a derivatization reagent quantity of 10 µL, a GC injection of 1 µL, a split ratio of 1:10, and 100% efficient extraction, about 2 pmol of Glu would be sent to the GC column, which is consistent with an allowed detection based on predicted detection limits at 0.03 to 5 pmol (0.5 pmol for glutamic acid) for amino acid chemical standards which do not require extraction from a mineral matrix [START_REF] Rodier | Detection of martian amino acids by chemical derivatization coupled to gas chromatography: In situ and laboratory analysis[END_REF]. A comparable calculation for the least abundant amino acids (e.g., isoleucine) identified in Atacama samples, which had concentrations on the order of 1 ng of amino acid per gram of sample, estimates about 0.002 pmol of a given amino acid would be sent to the GC column, which is below the lowest detection limits (0.05 pmol for isoleucine), again, for amino acid chemical standards which do not require extraction from a mineral matrix (Rodier et ). Since amino acids, including glutamic acid, is not detected in our experiment, there are several possible explanations. These explanations are listed below and then discussed, accompanied by some proposed tests.

(1) The extraction efficiency of the solvent extraction or thermodesorption coupled to derivatization is not 100%. Specifically, for the thermodesorption, the protocol (duration, temperature) may not be optimal for extraction of amino acids from this sample. (2) Amino acids are lost in cold spots or during transfer of the sample during sample preparation (3) The derivatization reaction is inhibited by the presence of water or the mineral matrix and/or the derivatization reaction (duration, temperature) is not optimal for the detection of amino acids present in the given sample.

This experiment and interpretations of its results highlighted a gap in current understanding of the extraction efficiency of thermodesorption parameters which are compatible with the adjustability of MOMA. Thermodesorption is an optional protocol which can be utilized on MOMA in order to aid in extraction of organic molecules from a mineral matrix. However, the efficiency of thermodesorption to extract target compounds such as amino acids at different temperatures and durations in relationship to more conventional extraction techniques is not characterized within the adjustability of MOMA. For example, [START_REF] Buch | Development of a gas chromatography compatible Sample Processing System (SPS) for the in-situ analysis of refractory organic matter in martian soil: preliminary results[END_REF] have shown that amino acids that are strongly chemically bound to Atacama samples can be desorbed intact (i.e., without significant chemical degradation) through a heating protocol of 500˚C for 5 minutes. However, thermodesorption on its own could not be implemented in this way on MOMA since the MTBSTFA derivatization capsule will be released at 221˚C. Therefore, a proposed test for laboratory experiments that aim to demonstrate detection of amino acids from natural samples using derivatization-GCMS is to conduct a series of tests comparing the extraction efficiency of traditional solvent extraction (aided by sonification) with thermodesorption across duration and temperature protocols that are compatible with MOMA. If this comparison is characterized, one would be able to quantify the relative efficiency of extraction (desorption) by thermodesorption against a well-characterized technique. A non-detection could then be quantitatively explained by the expected extraction efficiency of thermodesorption parameters.

The calculation above for the amount of nanomoles of an amino acid that would be sent to the GC column are at the limit of detection of the instrument, even for the most abundant amino acid in the sample. In addition, this calculation does not account for losses due to cold spots in the sealed ampule or due to the multiple transfers of the sample throughout the offline derivatization protocol. The sample is transferred between vials/ampules/syringes several times throughout the process (Figure 80). The sample is also heated more than once (first for the thermodesorption step, then the derivatization step). The multiple transfers of the sample and the potential creation of cold spots, especially in an ampule sealed by flame which has an original shape during each test, could result in the adsorption of organics in the glass vial or ampule after they have been extracted from the mineral matrix. A possible solution would be to conduct tests with higher sample masses (100-200 mg per test rather than 5-10 mg per test). This solution would also help with a practical limitation as to how much the ratio of derivatization reagent to solid sample can be decreased for the purposes of minimizing the dilution factor at the offline derivatization step (Chapter IV, Section IV.3.2.3.2). Additionally, the actual ratio of derivatization reagent to regolith sample on MOMA could be mimicked, since ~100 to 200 mg of sample are expected and 15 µL of reagent will be applied to the sample from the MOMA capsules. The caveat is that larger total sample sizes would need to be acquired for optimization studies. Additionally, a potential solution that could be used in combination or on its own would be to conduct preliminary tests first using natural samples with higher concentrations of amino acids, such as garden soil.

The derivatization reaction itself could be inhibited by the presence of water or the mineral matrix. Additionally, the derivatization reaction (duration, temperature) may not be optimal for the detection of amino acids present in the given sample. In the case of thermodesoprtion, a drying step may be incorporated. In the case of solvent extraction, the extract is dried prior to derivatization, but water will always be remaining in the sample. For example, DMF is hydrophilic. With very trace levels of organics, even small amounts of water may compete for the derivatization reagent. [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF] shows that the MTBSTFA reagent is not deactivated by interaction with a different Atacama sample.

The detection of amino acids using this kind of offline direct derivatization has been demonstrated with spiked samples. For example, in Chapter IV, it is demonstrated that offline direct derivatization as described here with organics at 0.1, 1 and 5 wt. % concentration of organic compounds are detectable with offline direct MTBSTFA derivatization and no separate extraction step. It was also shown in Chapter IV that given target molecules even within the same chemical family can have different trends and responses under the same derivatization protocol (with DMF-DMA derivatization, Section IV.3.2.3.2). Therefore, ideal samples selected for wide-ranging thermodesorption and derivatization studies would contain multiple amino acids or other target compounds at concentrations for which observation is consistent and quantifiable. This kind of protocol could be an option for optimization studies of thermodesorption and derivatization protocol. However, it is not possible to say affirmatively or not that it will be a viable option for optimization studies targeting amino acids since a detection of amino acids from a natural sample using direct offline derivatization has not yet been demonstrated by this thesis or in the literature (e.g., [START_REF] Siljeström | Comparison of prototype and laboratory experiments on MOMA GCMS: Results from the AMASE11 campaign[END_REF]. [START_REF] Brault | Etude de l'efficacité de la fonctionnalisation des acides aminés au MTBSTFA après hydrolyse acide et dans différentes matrices minérales analogues martiennes : application aux expéri-ences Sample Analysis at Mars (SAM) et Mars Organic Molecule Analyzer[END_REF] showed how the mineralogical nature of the mineral matrix of a natural sample can lead to a reduction in the yield of derivatized amino acids. The yield of derivatization was retrieved through an added drying step prior to derivatization to remove the adsorbed water. These tests did not test the detection of amino acids indigenous to the natural samples. Rather the MTBSTFA reagent was applied directly to a soil sample and heated at 75˚C for 15 minutes, before the supernatant was extracted and added to an amino acid chemical standard solution and derivatized at 75˚C for 15 minutes. One test was implemented in which a Río Tinto sample was spiked with what was determined to be an "optimistic" amino acid concentration (1.39 ppm) in martian surface samples, which was lower than the amino acid chemical standard used for the majority of the tests in the study. At these lower concentrations, only traces of the amino acids were identified in XIC.

The conclusion was that either too much non-structural water in the soil (which was not removed during the drying step) caused a preferential reaction of MTBSTFA with water instead of the amino acids or that the amount of derivatized amino acids injected to the GC was below the detection limit of the instrument. This result is consistent with our result, since low concentrations of spiked samples (only partially adsorbed to mineral surfaces) revealed only traces of amino acids.

Here, the detection is more challenging, since low concentrations of amino acids are coupled to the challenge of desorping them from the mineral matrix.

V.3.2. Reactor online derivatization

Samples can be introduced to the reactor bed in two ways: (1) through a syringe injection through the liquid inlet (Figure 82) which is fitted with a custom-cut miniature septum, and (2) by deposition inside the 1.5 mL reactor chamber (Figure 82). An online experiment with 41.1 mg of JSC Mars-1 in the reactor bed was conducted and the chromatogram is shown in Figure 84 along with the MTBSTFA/DMF blank run. The sample was heated in the reactor bed as the reactor was ramped (room temperature to ~210˚C in 20 minutes, ~9.5 ˚C•min -1 ) to its final set temperature (~210˚C). 3 µL of MTBSTFA/DMF (4:1) was added to the reactor chamber by 5 µL SGE liquid syringe through the liquid inlet of the reactor and the sample underwent derivatization at ~210˚C for 5 minutes. A suite of mostly straight-chain carboxylic acids were detected in the test with JSC Mars-1 in the reactor bed after online derivatization above the derivatization blank. There were additional peaks visible in the sample run which were not present in the blank, but compound assignment was not possible due to the signal being too close to the noise limit and/or coelutions. The carboxylic acids which were identified are all molecules that were identified with solvent extraction + MTBSTFA derivatization in previous tests, except derivatized benzoic acid and 1-decanol [START_REF] Morisson | TMAH Thermochemolysis of a Martian Regolith Simulant: Optimization of an Analytical Method for the Detection of Trace Organic Matter by the MOMA-Pyr-GC-MS Experiment Onboard the ExoMars-2020 Rover[END_REF]. Even though it is convincing that certain carboxylic acid signals come from the sample due to the increase in response from the blank after the sample is introduced, certain signals (i.e., derivatized lactic acid, benzoic acid, octanoic acid, glycolic acid, nonanoic acid, 1-decanol, decanoic acid, dodecanoic acid, and hexadecanoic acid) continue to appear at comparable magnitudes to those observed in the sample test in multiple tests run after the online derivatization of the sample even when only MTBSTFA/DMF is injected as a derivatization blank. The levels of these putative derivatized carboxylic acid peaks remain at similar abundances even when the Tenax was removed from the trap, the injector liner was thoroughly cleaned, and the flow path was changed so it no longer passed through the reactor, provoking the question if the compounds are contamination in the MTBSTFA source itself or if they could be produced from the heating of the MTBSTFA at these higher derivatization temperatures (~200˚C). However, as shown in Figure 84, derivatized benzoic acid, hexadecanoic acid and octadecanoic acid are the only carboxylic acids that appeared in the first online derivatization blank before ~40 mg of JSC Mars-1 were introduced to the reactor bed. Derivatized propanedioic acid and tetracosanoic acid, the two most abundant carboxylic acids previously detected in a sample of JSC Mars-1 by solvent extraction and MTBSTFA derivatization [START_REF] Morisson | TMAH Thermochemolysis of a Martian Regolith Simulant: Optimization of an Analytical Method for the Detection of Trace Organic Matter by the MOMA-Pyr-GC-MS Experiment Onboard the ExoMars-2020 Rover[END_REF] are not identified, which may be evidence that the identified carboxylic acids are not coming from the sample or are due to differences in the extraction techniques and their efficiency to extract certain molecules.

The origin of the putative derivatized carboxylic acid signals is not yet fully understood. Possible origins to these signals are suggested.

(1) The compounds are not derivatized carboxylic acids, but rather some other derivatization byproduct of MTSBTFA in the presence of DMF with a similar mass spectrum. (2) The compounds are contamination in the injector system or in the stock solution of MTBSTFA or DMF which come either from hand oils during sample handling in the laboratory or from the synthesis of the chemicals during fabrication. (3) The compounds are derivatized carboxylic acids which are produced as reaction products of MTBSTFA in the presence of DMF at these temperatures.

It was not possible to conduct additional laboratory tests after the online derivatization run of JSC Mars-1, but previous derivatization blanks across different derivatization protocols and with varying injection quantities are utilized opportunistically in order to try and understand more about the appearance of these compounds. Three sets of blanks are shown in Figure 85 to help and provide evidence to the possible origin of these compounds. The details of each experiment are given in the caption of Figure 85.

The derivatized carboxylic acid signals were seen in tests when the reagent was heated online at 210˚C for 5 minutes, and the signals were not seen in tests in which the reagent was heated offline at 75˚C for 15 minutes. However, the amount of reagent introduced to the instrument is very different between these two cases (0.5 µL for the offline derivatization, 3 µL for the online derivatization) so it is possible that the signals in the online tests are due to low levels of contamination in the MTBSTFA or DMF solutions which are only detected when higher amounts of the solution are introduced to the system rather than due to the temperature difference in the derivatization reaction. Therefore, data from a past study was utilized, shown in the top panel of Figure 85, which shows a comparison of offline derivatization of MTBSTFA/DMF under two different derivatization protocols (250˚C for 3 minutes and 75˚C for 15 minutes) in which the same amount of solution (0.5 µL) was injected by syringe to the GC-MS in each case. The derivatized hexadecanoic acid and octadecanoic acid were only observed in the chromatogram for which the sample had been heated at 250˚C for 3 minutes. In the bottom panel of Figure 85, the derivatization blank and the sample test of the reactor online derivatization of JSC Mars-1 is compared but now in XIC (m/z 313, 341) to target the putative carboxylic acids of interest. The signal which is identified as derivatized hexadecanoic acid has about the same peak area in the blank and sample run, but the derivatized octadecanoic acid signal is only present in the derivatization blank run. These examples show how important it is not only to test the derivatization reaction at temperatures that mimic those to be utilized on the space experiment (e.g., 250˚C) but also on experimental systems which more closely mimic the space experiment and can introduce nuances to the results.

Other carboxylic acids, such as benzoic acid, were also detected in derivatization blanks. Deconvoluting a terrestrial or martian source for benzoic acid is a challenge for space experiments. There are several possible paths to production of benzoic acid originating from a natural sample. [START_REF] Benner | The missing organic molecules on Mars[END_REF] predicted that non-volatile organic salts such as benzoic acid or other benzenecarboxylates derived from the oxidation of meteoritic organic matter would accumulate in the upper meter of the martian surface with concentrations up to 500 ppm by weight. Benzoic acid is also a possible precursor of the chlorobenzene that was detected on Mars in the Cumberland samples, which was demonstrated to be indigenous to the martian parent sample [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. Chlorobenzene can be produced by reactions between benzoic acid and perchlorate at elevated temperatures (Freissinet et al. 2019;[START_REF] Millan | Etude de la composition de la surface de Mars : recherche de molécules organiques par analyse physico-chimique in situ avec l'instrument SAM de la mission Mars[END_REF]. Another possible source of benzoic acid is the Tenax-TA adsorbent used for trapping in the case of the online reactor derivatization experimental setup. Tenax-TA, a polymer made of 2,6-diphenyl-p-phenylene oxide, releases aromatic compounds from both thermal and chemical degradation when heated to 300°C [START_REF] Buch | Role of the Tenax® Adsorbent in the Interpretation of the EGA and GC-MS Analyses Performed With the Sample Analysis at Mars in Gale Crater[END_REF][START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF]. Phenol is a known degradation product of Tenax that has also been detected in its derivatized form in several SAM GC-MS runs as well as in laboratory experiments involving Tenax-TA [START_REF] Buch | Role of the Tenax® Adsorbent in the Interpretation of the EGA and GC-MS Analyses Performed With the Sample Analysis at Mars in Gale Crater[END_REF]) and which could be converted to benzoic acid in an oxidizing environment [START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF].

Directed searches were performed for the amino acids previously detected in JSC Mars-1 [START_REF] Morisson | TMAH Thermochemolysis of a Martian Regolith Simulant: Optimization of an Analytical Method for the Detection of Trace Organic Matter by the MOMA-Pyr-GC-MS Experiment Onboard the ExoMars-2020 Rover[END_REF], which included derivatized valine, leucine, isoleucine, proline, 5-oxoproline, and phenylalanine. No amino acids were identified in the chromatogram, despite the fact that some of the carboxylic acids detected (e.g., derivatized octanoic acid, dodecanoic acid, tridecanoic acid) were quantified at similar or lower abundances in the sample than several amino acids. This could be explained if the carboxylic acids detected in our tests are from contamination, although higher abundances are present in the test with the sample than in the derivatization blank.

The extraction technique could also affect this result, since solvent extraction (1:1 H2O to isopropanol) is a more efficient extraction technique for amino acids than thermodesorption. Thermodesorption has been shown to be an effective replacement for solvent extraction for the extraction of amino acids in a natural sample, but at temperatures of 500˚C for 5 minutes (Buch et al., 2009), which are not compatible with MOMA operations since the eutectic capsule for MTBSTFA will open at 221˚C. The reactor setup, as shown here, is capable of heating samples to these temperatures (i.e., 221˚C).

These results are consistent with other online derivatization experiments of natural samples. For example, tests with the same miniature homemade reactor linked to a COTS GC-MS [START_REF] Meunier | A laboratory pilot for in situ analysis of refractory organic matter in Martian soil by gas chromatography-mass spectrometry[END_REF] showed detection of amino acids from a garden soil sample, but not from an Atacama sample. A similar type of setup which enabled online derivatization and direct transfer in the gas phase to a COTS GC-MS, reported on the results of amino acid chemical standards spiked on SiO2, lyophilized pseudomonas mixed with silica, and Atacama samples tested on this system (David et al. 2016). This study (David et al. 2016) showed the influence of a mineral matrix to inhibit the detection of amino acids at different temperatures. For example, when amino acids were derivatized on a silica matrix at 80˚C, there was a drastic loss of high molecular weight amino acids in comparison to chemical standards, potentially due to a partial adsorption of amino acids on the silica. The recovery of amino acid derivatives decreased when MTBSTFA derivatization was performed at higher temperatures (i.e., 300˚C) possibly due to incomplete silylation of trisubstituted amino acids (e.g., serine), the release of water from the mineral, enhancement of catalytic effects of the matrix, and low thermal stability of amino acids when submitted to temperatures higher than 200˚C (since these amino acids were spiked onto the mineral). Detection of amino acid derivatives failed when derivatization was performed on an Atacama sample. This result was attributed to the iron composition of Atacama sample that could inhibit the reaction [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF]. However, as mentioned in Section V. 3.1, Buch et al. (2006) demonstrated that the mineral matrix of the Atacama sample tested in their study did not deactivate the MTBSTFA reagent. It was also not mentioned that DMF was used as a solvent for MTBSTFA in the experiments of David et al. (2016), and the presence of DMF is known to enable a better response for amino acids [START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. The tests presented here, in combination with the results from the literature, reveals a gap in understanding more about the non-detection of amino acids in laboratory derivatization experiments across different natural samples. Next steps and recommendations for laboratory experiments are proposed throughout this chapter and summarized in Section V.5.

V.4. Perspectives for future laboratory testing

V.4.1.

Evaluation of experimental setups

Table 26 summarizes the evaluation of laboratory-based experimental setups which enable laboratory testing of MOMA-like thermodesorption and derivatization protocol for the detection of trace levels of target compounds such as amino acids. The advantages of offline derivatization are the simplicity of the required experimental setup. This protocol requires only a COTS GC-MS with no additional setup and a way to perform derivatization offline with a benchtop method. The detection of amino acids from a natural sample using this technique has not yet been demonstrated.

The main disadvantages of this protocol for mimicking the space capability to detect trace levels of amino acids are the low amounts of potentially derivatized target compounds that are sent to the GC and which may be below the detection limit of the instrument, especially if the thermodesorption step does not efficiently extract amino acids from the mineral matrix, as well as multiple transfers of the sample throughout the protocol which results in undetermined loses.

Additionally, in terms of demonstrated detection of target compounds, this setup has a lower fidelity likeness to the space experiment, in that the setup does not consider the online derivatization, the transfer of the sample through a system of transfer lines, and adsorption/thermal desorption trapping and injection, which has been shown to potentially trap molecules of a certain molecular weight across multiple trap flashes or indefinitely [START_REF] Millan | In situ analysis of martian regolith with the SAM experiment during the first mars year of the MSL mission: Identification of organic molecules by gas chromatography from laboratory measurements[END_REF].

The advantages of an online derivatization laboratory set-up are that it more closely mimics the space experiment as it includes a separate reactor for thermodesorption and derivatization, out of the path of helium flow, before the sample can be transferred to an injection trap composed of Tenax TA and is injected to the GC column. Since the resources of ETU and Testbed systems are very precious, this kind of laboratory setup, especially for studies that require large numbers of GC-MS runs and which require higher fidelity to the space experiment, are valuable. This setup enables a full transfer (depending on the efficiency of the transfer line system and injection trap) of derivatized materials to the GC column. For example, an analogous calculation to that given in Section V.3.1 for offline direct derivatization, assuming a sample size of 100 mg in the reactor bed, a derivatization reagent quantity of 10 µL, no split, and 100% efficient extraction, about 1200 pmol of Glu would be sent to the GC column (versus 24 pmol in the direct offline derivatization experiment). This enables not only a higher likelihood of detection by the instrument and strict identification of the amino acid derivative, but also a higher likelihood of the signal being above the limit of quantification and therefore useful for thermodesorption and derivatization protocol optimization studies.

Disadvantages of an online laboratory system are its complexity both in terms of construction, calibration, and operations. The experimental setup includes a homemade reactor which is not commercially available and therefore, the setup is not easily replicable as it is described here. Also, the additional transfer lines and the use of injection trapping adds complexity to the potential for odd peak behavior (as described in Section V.4.2) and therefore increases the setup and calibration time necessary to ensure that a comparable response can be procured between the transfer of a species through the reactor pathway versus through a conventional direct injection to a GC inlet.

In the case of the online laboratory setup that is described in this thesis (Section V.2.2.2), an alkane chemical standard mixture (Section V.2.2.1) was used for a series of calibration tests which compared injection efficiency through the Optic 4 injector by syringe (standard COTS GC-MS system injection) and through the reactor as described in the materials and methods (Section V.2.2.2). Information from these calibration tests are used opportunistically for comparison to flight systems in the following sections.

V.4.2. Peak behavior on non-COTS laboratory systems: applications to the space experiment

V.4.2.1. Peak behavior on homemade laboratory setup during set-up and calibration

The intention of this homemade system was to perform online derivatization of natural samples in order to demonstrate the capability of MTBSTFA/DMF to extract and derivatize amino acids in a Mars-like sample. However, prior to running natural samples on the system, an alkane mixture (composed of 2-methylnonane, decane, and dodecane diluted in cyclohexane) was injected on the reactor and on the Optic 4 injector in order to confirm that the peak response (peak area) and the peak shape is consistent and well-separated across the gas sample processing system. These tests were run throughout the experimental setup construction and calibration, and therefore some features of the peak behavior are not considered nominal features. However, this auxiliary data is used opportunistically to discuss potential challenges that could be experienced by ETU and flight models given a more complex gas processing and injector system and possible explanations and solutions. At least two important aspects of calibration are studied and are related: (1) the elimination of odd peak behavior such as double or multiple peaks and (2) confirming that the chromatographic response, by the quantification of peak area for a given species, is consistent between a syringe injection directly on the column (i.e., using the Optic 4 as a conventional GC inlet) and an injection through the reactor (Figure 82). This comparison demonstrates that significant parts of the sample are not lost through the gas processing system and injection trapping. This section presents observed odd peak behavior which is relevant for space experiments which utilize more complex gas sample processing systems, in which cold spots can arise, and adsorption/desorption trapping. Line and trap temperatures and conditions which may provide context to any odd peak behavior observed in flight-like data.

Examples of each type of odd peak behavior identified in the homemade laboratory setup tests are shown in Figure 86 and Table 27. There are two important transfer lines in the setup which are both heated by auxiliary sources: the transfer line between the reactor and the 6-way valve (Line 1) and the transfer line between the 6-way valve and the Optic 4 (Line 2). Prior to adding the heating element to Line 2, injections of the alkane mixture were made both on the reactor and on the Optic 4. These two tests are shown in the top left panel of Figure 86. These tests are the only examples from the laboratory tests in which broad peaks are observed. This observation is consistent with the idea that broad peaks can be due to cold spots in the system.

Table 27 catalogs non-nominal behaviors, or "odd" peak behaviors this relevant laboratory setup in order to determine any potential trends and behavior. Possible explanations corresponding to general types of causes for weird peak behavior are outlined.

Trapping was initially performed by freezing the Optic 4 without the use of Tenax TA. Initially, the trapping temperature was about -30˚C and shoulder peaks occurring after the main peak were observed (red curve in top right panel of Figure 86). This is an example of shoulder peaks resulting from the trapping and injection conditions rather than from a saturation of the column by a high injection amount of a given species. The double peaks are likely occurring because part of the analyte is injected when the trap begins to heat and there is a wider or double peak due to the time differential between the trap heating start and the maximum trap temperature (300˚C in the laboratory). The laboratory flash heating case is better than the MOMA case, in which the trap reaches its maximum temperature in less than 10 seconds whereas on the MOMA FM it is a minimum 10-15 s. In order to improve the peak shape, the time differential between the trap heat start and the maximum trap temperature was decreased by increasing the trapping temperature to -20˚C. Although shoulder peaks were still observed (black curve in top right panel of Figure 86), the shoulder peak was closer (along the x-axis) to the main peak. When the trapping was performed at -20˚C without Tenax, the shoulder shifted to appearing before the main peak for 2-methylnonane and decane and continued to appear after the main peak for dodecane. This is an example of how (1) shoulder peaks may not appear consistently before or after the main peak even under the same run conditions and may vary depending on the compound and (2) a difference in the trapping temperature may alter the peak appearance and behavior of multiple peak occurrences. This challenge may also be combined with an inefficient transfer of solute through the gas processing system, especially since the line temperature of the system was only at 100˚C and the peak areas of the two cases are different (top right panel in Figure 86). This example illustrates the complexity of peak behavior on systems which include more complex gas processing systems and thermal adsorption/desorption trapping, and which can provide context information for interpreting flight system data. was not yet heated. This test is not part of the nominal study, since the line was not yet heated, but is used here opportunistically in order to aid in the discussion of odd peak behavior in complex laboratory and space systems. (Top Right) Injection on reactor without Tenax TA present in Optic 4 liner and with the trapping temperature at -30˚C or -20˚C. (Bottom Left) Injection on reactor after 30 mg of Tenax TA has been added to the Optic 4 liner and before the Tenax TA has been conditioned at 280˚C for 24 hours. Again, this test is not part of the nominal study, since the Tenax was not yet fully conditioned, but is used here opportunistically in order to aid in the discussion of odd peak behavior in complex laboratory and space systems. (Bottom Right) Injection on reactor or on Optic 4 with Tenax TA present in the Optic 4 liner and with the trapping temperature at -20˚C or 0˚C. ( 1) 2-methylnonane, (2) decane, (3) dodecane, (4) decanal, (5) 1-decanol, (6) chlorinated straight-chain alkane. All plots are in XIC (m/z 57+71). It is not determined from where these compounds originate, if they are from contamination present in the lines or are produced by a reaction in the system.

Even after the addition of Tenax TA to the Optic 4 injector liner, double peaks were observed before the main peak of each alkane when the mixture was injected on the reactor at -20˚C. The cause of this specific double peak phenomena is not fully understood. There are at least three possibilities. The double peaks could still be due to the longer injection time. When the trapping temperature was increased to 0˚C, the sharp double peaks before each alkane peak were no longer observed. However, the mass spectrometer response decreased at the same point by about an order of magnitude. This is shown by the smaller peak areas of the tests with a trapping temperature of 0˚C (bottom right panel of Figure 86). Indeed, a wide double peak appears before the main dodecane peak in some of the runs when the trapping temperature is at 0˚C both with a reactor injection and an Optic 4 injection. Therefore, it's possible that even with the higher trapping temperature, the double peaks still occur but are too close to the noise limit to be visible. The wide peak shape of analytes close to the noise limit is consistent with other laboratory tests (Chapter IV, tests with DMF-DMA, Figure 62). Second, the double peaks could be due to a cold spot and a collection of analytes over time, based on the fact that the ratio of the first peak area to the second peak area of a given alkane increases over the course of three tests with the same experimental conditions. However, the sharp peak shape is not generally consistent with a cold spot. Finally, the double peak behavior could be due to the fact that the Tenax-TA was not solidly secured within the Optic 4 liner and was shown to have shifted up the injection column. For tests performed with solid natural samples discussed in the Section V.3.2, silica wool was placed above the Tenax TA inside the injector liner in order to secure it.

Figure 87 shows a comparison between the same alkane mixture of nonane, 2-methyl, decane and dodecane injected on the reactor and on the Optic 4 following the troubleshooting of odd peak behavior that has been described. The peaks are well separated and the peak shape is generally sharp. However, the lower response in the Optic 4 injection test is likely due to a decrease in the mass spectrometer response at this point during the testing due to a dirty ion source. The Air/Water background had been tracked throughout the testing, and a drop in this signal correlated linearly with the decrease in the alkane signals in the Optic 4 test. It could also be due to the slight double injection which is visible at least for the dodecane peak in the chromatogram (Figure 87, left panel) signifying that even if increasing the trapping temperature improved the injection efficiency, the double peak issue is still not completely solved. This decrease in response is critical to address before further testing since limit of detection is so important for these studies with trace amounts of organics in solid natural samples.

V.4.2.2. Discussion of double peak behavior in context of space experiments

This section provides categories and, in some cases, suggests specific origins to odd peak behavior that can arise in systems which utilize complex gas pathways and adsorption/thermal desorption trapping. This kind of context data will assist the MOMA team in making efficient and informed decisions during operations on Mars, in which there will be limited time to interpret data and suggest necessary edits to software scripts and system conditions within the adjustability of the flight model. Table 28 gives a summary of potential general explanations and correlations to the origin of an observed odd peak behavior.

There were examples of double peak behavior or other non-nominal chromatographic peak behavior during functionality testing of a MOMA ETU during the GSFC ETU tests introduced in Chapter III (Section III.2.3,III.3.4). A summary of these peak behaviors is shown in Figure 89. [START_REF] Buch | Role of the Tenax® Adsorbent in the Interpretation of the EGA and GC-MS Analyses Performed With the Sample Analysis at Mars in Gale Crater[END_REF].

# Oddity in laboratory data Run occurrences

1 A peak appears earlier than expected in the run, in addition to peak at the expected retention time. The peak has a smaller peak area than peak at expected retention time. The two peaks are fully separated.

1.1. Alkane peaks in tests with Tenax TA, trapping temperature at -20˚C (bottom right panel of Figure 86).

2

A peak appears later than expected in the run, in addition to peak at expected retention time. The peak has a smaller peak area than peak at expected retention time. The two peaks are fully separated

No occurrence identified in laboratory data.

3

A peak appears at the expected retention time with a shoulder peak of the same compound immediately after or before.

3.1. Shoulder peaks of alkane peaks before and after peak at expected retention time, trapping temperature is at -20˚C (before) and -30˚C (after) (top right panel of Figure 86). 4

A wide or very wide peak appears later than expected in the run. No peak at the expected retention time. Ghost peak.

Not possible to confirm in laboratory data.

5

Benzene or toluene as trap degradation products are missing or at unexpected ratio.*

No benzene or toluene from trap degradation identified in lab data. 6

A wide or very wide peak at expected retention time.

6.1. Wide peak of 1-decanol (Injection on reactor, top left panel of Figure 86). 6.2. Wide peak of 1-decanol preceded by a sharp peak of decanal and a sharp peak of a chlorinated straight-chain alkane (Injection on Optic 4, Figure 86). 6.3. Wide alkane peaks in tests without Tenax TA, trapping temperature at -20˚C (same conditions as 1.1) 7

A wide or very wide peak at unexpected retention time, in addition to a peak at the expected retention time.

No occurrence identified in laboratory data.

8 Multiple peaks (>2) of the same compound occur either before or after the expected retention time. These multiple peaks are in addition to a peak at the expected retention time or it is undetermined if there is a peak at the expected retention time.

8.1. Multiple peaks of alkane fragments, i.e., m/z 57, 71 (bottom left panel of Figure 86).

There is a double peak of benzene (Oddity 1/2), coming from trap degradation, an example of which is shown in the bottom right panel of Figure 89. The ratio of the peak area of the first peak of benzene to the peak area of the second peak of benzene varies across a range >1 and <1. There is a wide peak of derivatized carboxylic acid (m/z 74 and 87) appearing before a sharp peak of decanoic acid, methyl ester appearing at a later than expected retention time (Oddity 4) which is pictured in the bottom left panel of If double or multiple peaks appear with a sharp peak shape, the most likely cause is the trapping and injection. One hypothesis is that there is a kind of double injection due to the programming of the injection which is shown in Figure 88. The opening of Valve 1 in Figure 88 marks the flow path switching to go through both the trap and the column, but there is a delay between this marker and the flashing (heating) of the trap. After the trap flashes, the trap is cooled before the flow path is changed again to bypass the trap and start the temperature ramp of the column.

Another cause of double or multiple sharp injections can be due to a low trapping temperature and the duration of the flash heating of the trap, which can result in a long injection. This is illustrated in the laboratory test examples (Section V.4.2.1) when the trapping temperature was -30 and -20˚C without Tenax-TA. Parameters such as injection trap temperatures over the course of the injection, the maximum trap temperature during injection, and duration of the trap heating (∆t between the start of the trap heating and the time at the maximum trap temperature) could affect peak behavior. The hypothesis would be that lower trapping temperatures correlate to the appearance of double or multiple peaks due to a longer injection. Additionally, tests in which the trap temperature is ramped to a higher temperature after a run in which the flash heating was lower might desorb some analytes left on the trap from previous runs.

In general, very broad peak behavior can be associated with a cold spot in the system rather than an injection issue, since cold spots can act as traps for species as they pass through the system which may be released slowly once there is a temperature change at the element. Adsorption or chemisorption of analytes can occur on internal surfaces and may not be released depending on the line temperature or may be released when a specific element is heated. Temperature profiles, especially those GC-relevant temperatures between the IT and the GC column are potential origins of system cold spots or temperature differentials which could cause odd peak behavior, including for MOMA: valve plate temperatures, column capillaries, trap capillaries, column temperatures, and trap plate temperatures. Peak behavior may vary by molecule since molecules with higher molecular weight and/or less volatility may collect more easily within the system. A peak appears at the expected retention time with a shoulder peak of the same compound immediately after or before.

3.1. Nature of interaction between a compound and separation of that compound by the column (e.g., 3-methylhexane). 3.2. Saturation of the column due to amount injected of a species. 4

A wide or very wide peak appears later than expected in the run. No peak at the expected retention time. Ghost peak.

2.1. Gas flow pathway and heating elements associated with a specific GC column or pathway.

5

Trap degradation products are missing or at unexpected ratio.

5.1. Trapping parameters such as the maximum heating of the trap during injection.

6

A wide or very wide peak at expected retention time. 6.1. Gas flow pathway and heating elements associated with a specific GC column or pathway. 6.2. Saturation of column or ion trap. 6.3. Peak very close to noise limit. 6.4. Long injection time (wide, not broad) 7

A wide or very wide peak at unexpected retention time, in addition to a peak at the expected retention time.

7.1. Gas flow pathway and heating elements associated with a specific GC column or pathway. 7.2. Saturation of column or ion trap. 7.3. Nature of changing run parameters due to troubleshooting nature of functionality tests (e.g., sample left on the trap or injection on column without collection of MS data). 8

Multiple peaks (>2) of the same compound occur either before or after the expected retention time. These multiple peaks are in addition to a peak at the expected retention time or it is undetermined if there is a peak at the expected retention time.

8.1. Saturation of column due to amount injected. 8.2. Compounds of different molecular weights experience different adsorption and desorption properties.

The quantity of analyte sent to the GC column may also play a role in peak behavior. Saturation of the GC column and/or ion trap due to high injection amounts of chiral alcohols in GSFC ETU tests showed sharp double and multiple peak behavior across two additional blank tests (top panels of Figure 89). Forms of saturation due to a high injection amount may also cause broad and ghost peak behavior. First of all, saturation of the column and/or saturation of the ion trap at specific is an important task for preparing countermeasures and interpretations for Mars operations and Mars data interpretation. In addition to the difference in performance between the flight experiment and the laboratory, the number of peaks and the level of complexity of a chromatogram obtained from the pyrolysis and/or derivatization of a martian sample, which includes the presence of a mineral matrix, is significantly greater than those obtained through the injection of chemical standards. Likewise, the analysis and observation of background and odd peak behavior in the MOMA ETU informs prioritization of lab studies (e.g., quantification of trap degradation products and ratios of MOMA injection traps at flight-like conditions). However, the analysis of odd peak behavior should also not be confused with the nominal performance of MOMA on Mars, but rather an opportunistic analysis of data collected throughout functionality, characterization, and optimization testing on the ETU and FM which can form a database to assist the team in designing operation plans and in targeting parameter settings.

V.4.3.

Contamination and false positives

Due to high detection limits of space experiments as well as the fact that space experiments carry organic content (e.g., wet chemistry reagents, Tenax), the task to deconvolute terrestrial contamination from organic matter derived from martian sources is non-trivial [START_REF] Biemann | The search for organic substances and inorganic volatile compounds in the surface of Mars[END_REF][START_REF] Freissinet | Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars[END_REF][START_REF] Guzman | Identification of Chlorobenzene in the Viking Gas Chromatograph-Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars[END_REF]. MTBSTFA/DMF derivatization blanks are run in between any introduction of an amino acid standard solution or natural sample to the GC-MS system. Blanks with no injection cannot properly determine the cleanliness of volatile compounds such as amino acids, since derivatization enables the detection of these compounds by GC-MS. Especially in the case of offline direct derivatization, in which there are multiple transfers of the sample prior to injection to the GC, there are multiple potential sources of contamination throughout the process. Figure 90 shows the type of contamination control which was employed in laboratory testing and Figure 91 shows an example of amino acid background (i.e., derivatized alanine and glycine), confirmed by retention time, which can exist at levels either comparable to that coming from a sample test or still present but at levels significantly below the levels in the sample test. Contamination was found to be a challenge across all the wet chemistry setups that are discussed, with the contamination controls illustrated in Figure 90 needing to be carried out between almost every sample test. This poses a challenge for efficient testing of broad thermodesorption and derivatization parameters and also poses a high risk of a false positive.

In addition to a clean derivatization blank as a requirement for any demonstration of an amino acid in a natural sample, compounds are confirmed by the retention time of a chemical standard.

Confirmation by retention time is often necessary with natural samples due to the trace levels of organic signals with are not identifiable with NIST due to noise interference and interference by coelutions. Figure 92 shows how multiple signals were identified by NIST as derivatized glycine, however the retention time of derivatized glycine identified the peak much closer to the noise limit of the instrument. Even with the expansion of MTBSTFA mass spectral libraries due to the SAM space experiment, the databases are not comprehensive across derivatization temperature and duration regimes. Systematic studies of the MTBTSFA background at higher derivatization temperatures (200-300˚C) are needed and are in progress. Given the challenges demonstrated by contamination, false positives are a likely risk of such studies and must be treated robustly. Mitigation can be employed; for example, not running chemical standards on the same instrument as sample testing, if resources allow this, or otherwise following strict contamination control as outlined in Figure 90. Due to the iterative nature of optimization testing, it can be challenging to avoid issues with contamination otherwise, since standards are often needed to be run in between tests to corroborate interpretation of results in real element is not employed in the laboratory setup, it could affect the ability of the space experiment to detect a molecule of a given chemical family or molecular weight. For example, the results from Chapter III which discuss the compounds which will be visible during a nominal 35-minute MOMA GC run time do not consider the ITs. Currently, it is unknown how the MOMA ITs may restrict the detection of amino acids. Figure 93 shows a flowchart of different experimental categories including the GC column, the injector system, the derivatization system, and the extraction technique which when employed in a laboratory experiment can result in varying fidelities to the space experiment. The complexity of the sample and its fidelity to samples that are collected on Mars is independent and also tied to the experimental setup. For example, the quantity of sample which is under testing depends to some extent on the experimental setup and protocol. While Figure 93 depicts the extraction technique and the derivatization reaction is separate categories, the use of one pot/one step extraction and derivatization on space experiments is also a tandem operation which should be considered as such in the capabilities of laboratory setups intended to mimic space experiments.

In conclusion, the use of MTBSTFA in the presence of DMF for the derivatization of amino acids has been extensively explored using chemical standards and explored to a limited extent using mineral samples spiked with amino acid chemical standards (e.g., Chapter IV of this thesis). However, these types of studies do not always mimic the derivatization protocol which will be utilized on space experiments (e.g., temperature of derivatization, one-pot/one-step extraction and derivatization) nor can doped samples be used to test the efficiency of thermodesorption for the extraction of amino acids from a mineral matrix. Limited studies have demonstrated the detection of amino acids in natural samples with a SAM-like experimental setup: proline and leucine from a carbonate-rich stromatolite sample [START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF]) and alanine and proline in two separate Lake Hoare samples [START_REF] Bishop | Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA[END_REF]. There have been no demonstrated detections of amino acids in natural samples using a MOMA-like experimental setup and this is an area for future laboratory studies which may make use of the experimental setups discussed in this chapter. In addition to MTBSTFA, SAM and MOMA also have the capability to utilize TMAH thermochemolysis for which the detection of amino acids has been demonstrated with chemical standards and spiked mineral samples (Chapter IV, Section IV.3.2.4) and MOMA will have the capability to utilize DMF-DMA derivatization for the detection of amino acids and enantiomeric separation (Chapter III, Section III.3.3).

V.5. Conclusions

The following main conclusions and results which correspond to sections of this chapter are given below.

1. State of the art (Section V.1) i. Substantial studies exist of MTBSTFA derivatization of amino acids. However, the existing literature outside the planetary community covers mostly the analysis of chemical standards or extracts from natural samples. ii. A summary of MTBSTFA derivatization studies with amino acids with applications to space experimentation is presented in Table 25. iii. Two studies from the literature [START_REF] Bishop | Coordinated analyses of Antarctic sediments as Mars analog materials using reflectance spectroscopy and current flight-like instruments for CheMin, SAM and MOMA[END_REF][START_REF] Stalport | The influence of mineralogy on recovering organic acids from Mars analogue materials using the "one-pot" derivatization experiment on the Sample Analysis at Mars (SAM) instrument suite[END_REF]) using a SAM-like experimental setup have demonstrated limited detection of MTBSTFA derivatized amino acids: Ala and Pro ( each in a Lake Hoare sample) and Pro and Leu (Svalbard stromatolite). No AA were detected in other samples (JSC Mars-1, Río Tinto, Murchison, and an Atacama subsurface sample; two other Lake Hoare samples) using a SAM-like setup. iv. To date, there have been no experiments which demonstrate the detection of amino acids using a MOMA-like experimental setup with wet chemistry protocol within the adjustability of MOMA.

2. Laboratory experimental setups (Section V.3.1 and V.3.2) i. The low quantitates of target compounds sent to the GC and the multiple transfers of the sample during handling in the offline derivatization protocol are a challenge for detection of trace organics in natural samples in which small sample sizes (per test), i.e., 5-10 mg, are used. ii. Systems that enable online derivatization of natural samples (Section V.2.2 and V.3.2.) are preferred for the amount of sample sent directly to GC, but introduce increasing complexity and can introduce challenges of odd peak behaviors, although these behaviors may more closely mimic the space experiment.

iii. Preliminary results of a natural sample (JSC Mars-1) tested on a homemade reactor system for online derivatization shows detection of carboxylic acids and other organic signals coming from the sample, although contamination or contribution from the derivatization reagent itself has not been fully ruled out (Section V.3.2).

3. Perspectives (Section V.4) i. An evaluation of the suitability of the three experimental setups that were explored in Section V.3.1 and V.3.2 is presented in Section Error! Reference source not f ound.. ii. Experimental mitigation strategies are proposed for avoiding false positives due to contamination in laboratory studies (Section 0). iii. A summary of experimental parameters of the space experiment that may be mimicked in laboratory setups is given (Section V.4.4) and discussed in the context of the fidelity of laboratory experiments and expressed detections of amino acids and other target compounds in this thesis.

The following future studies and recommendations are proposed which correspond to the sections of this chapter are given below.

VI. Conclusions and perspectives

VI.1. Summary and linking to science questions

This thesis approaches its science and technical questions from the foundational scientific idea that life is composed of, and generates, organic matter. This thesis focuses on the search for organic matter using the Viking Lander GC-MS (Chapter II) and the future ExoMars MOMA GC-MS experiments (Chapter III, IV, V), with some applications to the MSL SAM experiment. Chapter II addresses the search for organic compounds on Mars by a reanalysis of the Viking GC-MS data based on new understandings of the martian surface environment since the Viking mission. A directed search for chlorobenzene is described, as well as a discussion of potential chlorine and carbon sources of the chlorobenzene molecule. Through this reinterpretation, this study addresses at least two of the fundamental questions of the thesis (Chapter I, Section I.4): §.1. Are there organic molecules on the surface of Mars and what are their nature and their abundance? §.2. What is the origin of the organic molecules detected?

Chapter III explores the capabilities of the MOMA chromatographic columns to separate and detect a range of organic and inorganic volatile compounds. This chapter demonstrates the importance of retention time libraries for interpretation of data on Mars and further addressing of §.1. once MOMA operates on Mars. These laboratory tests utilize flight spare columns, though do not consider certain flight-like components, such as adsorption/thermal desorption trapping and a complex gas processing system. Through comparison of lab data and ETU data, this study addresses directly at least two of the fundamental questions of the thesis (Chapter I, Section I.4): §.4 What are the capabilities and limitations of space instrument components to detect organic molecules on Mars? §.5 Are there analytical biases and/or constraints related to the flight-like GC-MS analysis, laboratory setups, and/or their fidelity to the flight experiments of interest?

Chapter IV explores the capability of the MOMA GC-MS package (pyrolysis-, derivatization-and thermochemolysis-GC-MS) to enable detection of organic compounds in the presence of a montmorillonite mineral matrix. This data set aids in addressing science question §.1. for current operations and interpretation of data sets on Mars. Additionally, this chapter addresses at least two of the following fundamental questions of this thesis (Chapter I, Section I.4): §.3 What is the role of the mineral matrix on the analysis? §.4 What are the capabilities and limitations of space instrument protocols to detect organic molecules on Mars?

Chapter V is a perspectives chapter which presents a survey of demonstrated detections of amino acids by MTBSTFA derivatization in the context of the fidelity of laboratory experiments to the

  Chapter I: Introduction to the investigation of organic matter on Mars by gas chromatography-mass spectrometry I.1. Astrobiology and the search for traces of life

Figure 11 :

 11 Figure 11: Three sequential eras characterized by surface weathering products proposed by[START_REF] Bibring | Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data[END_REF].

Figure 20 :

 20 Figure 20: Summary of thesis chapters with attention to the sample under testing and the fidelity of the experimental setup to flight-like experiments.

Figure 29 :

 29 Figure 29: Online derivatization, thermochemolysis and pyrolysis were performed by placing the sample in the oven in a variety of ways: (Top Left and Right) as amino and carboxylic acid solutions deposited on aluminum foil), (Bottom Left) as milligrams of solid sample placed in a Frontier pyrolysis cup, and alongside a MOMA derivatization capsule filled with either TMAH or DMF-DMA.

Figure 30 :

 30 Figure 30: Efficiency curves for the spare MOMA GC columns(Chirasil Dex, MXT 5). The efficiency of each column was studied at 60℃ and 120℃ for 1-butanol and chlorobenzene, to represent a range of operating temperatures to be used in flight. The efficiency curve for DL-alanine was studied at 115℃ since its retention time on the three columns, MXT 5, MXT CLP, and Chirasil Dex, was too high for tests using a lower isothermal hold, i.e. 60˚C. There are slightly different efficiencies for D-and L-Alanine on the Chirasil Dex column based on the column's ability to separate enantiomers. Therefore, each enantiomer has a different retention time and the number of theoretical plates (Equation3) is related to the retention time of each enantiomer.

Figure 31 :

 31 Figure31: Efficiency curves for the spare MOMA GC columns (MXT CLP, Q BOND). The efficiency of each column was studied at 60℃ and 120℃ for 1-butanol and chlorobenzene, to represent a range of operating temperatures to be used in flight, with the exception of the Q BOND column. The efficiency curve for DL-alanine was studied at 115℃ since its retention time on the three columns, MXT 5, MXT CLP, and Chirasil Dex, was too high for tests using a lower isothermal hold, i.e. 60˚C. Ethanol was studied at 115℃ to characterize the efficiency of the MXT Q BOND.

Figure 33 :

 33 Figure 33: C7-C40 alkanes solution run on the MXT 5 column. The x-axis scale represents a nominal MOMA run time of 35 min. (1) heptane, (2) octane, (3) nonane, (4) decane, (5) undecane, (6) dodecane, (7) tridecane, (8) tetradecane, (9) pentadecane,(10) hexadecane, (11) heptadecane, (12) octadecane, (13) nonadecane, (14) icosane, (15) henicosane, (16) docosane, (17) tricosane, (18) tetracosane, (19) pentacosane, (20) hexacosane, (21) heptacosane, (22) octacosane, (23) nonacosane. The GC column was heated from 45˚C to 220˚C with a 10˚C•min -1 ramp and held for a total run time of 35 min.

Figure 36 :

 36 Figure 36: (Top) DMF-DMA derivatized amino acids separated on the Chirasil Dex column. (1) L-serine, (2) Dserine (3) D-alanine, (4) L-alanine (5) DMF-DMA byproduct, (6) glycine, (7) DL-serine*, (8) D-valine, (9) L-valine (10) DL-leucine. (Bottom) A magnification of the above chromatogram showing the separation of DL-serine, DLalanine, and DL-valine.The GC column was held at 35˚C for 7 min, then heated to 182˚C with a 3˚C•min -1 ramp. DLglutamic acid was detected at a retention time of 44 min, and was not enantiomerically separated, but is not plotted here so that the separation of other enantiomers is clearly visible. *All the mass spectra of the derivatized amino acids, including L-D-serine, follow[START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF] Table 1. Peak 7 is an additional DMF-DMA derivative of DL-serine, possibly DL-serine, -dimethyl, -methyl ester.

Figure 37 :

 37 Figure 37: An illustration of the spread of retention times of tested compounds across a nominal 35-minute gas chromatographic run for each of the MOMA GC columns. The Compound Ref. # corresponds to the values given for each compound in Table12 and Table 13.

  detect straight-chain lipids in the form of alkanes, alcohols, and fatty acids with specific carbon patterns, indicating certain terrestrial bacteria and plant life.

Figure 39 :

 39 Figure 39: Chromatogram resulting from the GC-MS analysis of the AMASE KitKat sample, spiked with amino acids and derivatized with DMF-DMA, on the MOMA Chirasil Dex column. (Bottom) Total ion current; (Top Left) extracted ion chromatogram for m/z 70, showing the enantiomers of L-D-serine; (Top Right) extracted ion chromatogram for m/z 99 showing the enantiomers of D-L-alanine. The GC column was heated from 45˚C to 180˚C with a 10˚C•min -1 ramp and held for a total run time of 35 min.

Figure 40 :

 40 Figure 40: (Left) m/z 44 plotted along with the trap temperature curve for the first injection of 3-methylhexane (TID 8418). If the dead time is taken with t0 at the start of the trap heating, the unretained peak of CO2 appears at about 1 minute. (Right) Signals at m/z 45 and 61 appear before or mask signals of CO2 (TID 8422).

Figure 41 :

 41 Figure41:(Top) Chromatogram resulting from the analysis of a chemical mixture containing 2-butanol(1,2), 2pentanol[START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF]4), and 2-hexanol (5) on the MOMA Chirasil Dex column on the MOMA ETU. These results are not quantitative since these peaks were observed in a subsequent blank test following a test in which 20 nL of an equivolumetric mixture was injected to the ETU system, which was not used due to saturation of the GC column with this injection volume. The 2-hexanol chemical standard was in its L-enantiomeric form only, while the 2-butanol and 2-pentanol chemical standards are racemic mixtures. The column was heated at 40˚C (held for about 3 minutes) and then heated up to 180˚C at a rate of about 9˚C•min -1 . (Bottom) Chromatogram of a similar mixture of 2-butanol(1,2), 2-pentanol(3,4), and 2-hexanol (5,6) in the laboratory on a COTS GC-MS with the MOMA flight spare Chirasil Dex column. The column was heated at 35˚C (held for about 7 minutes) and then ramped to 182˚C at a rate of 10˚C•min - 1 . The dead time in the laboratory test was about 30 seconds.

Figure 42 :

 42 Figure 42: Retention times for (1) 3-methylhexane in the lab (black curve), (2) 3-methylhexane in the ETU test (TID 8418, second injection) based on taking the injection time at the maximum trap temperature (blue curve) and (3) 3methylhexane in the ETU test (TID 8418, second injection) based on taking the injection time at the start of the trap heating. For the lab test, the column was heated at 35˚C (held for about 7 minutes) and then ramped to 182˚C at a rate of 10˚C/min. The dead time for the lab test was 30 seconds. For the ETU test, the column was held isothermally at 37˚C.

Figure 43 :

 43 Figure 43: Retention times for (5, 6) L-D-serine in the lab (black curve), (1,2) L-D-serine in the ETU test (TID 8419) based on taking the injection time at the maximum trap temperature (blue curve), and (3,4) L-D-serine in the ETU test (TID 8419) based on taking the injection time at the start of the trap heating. For the lab test, the column was heated at 35˚C (held for about 7 minutes) and then ramped to 182˚C at a rate of 10˚C/min. The dead time for the lab test was 0.60 min. For the ETU test, the column was heated at 40˚C (held for about 3 minutes) and then ramped to 180˚C at a rate of about 9˚C/min.

  of complex samples require confirmation of compounds by retention time for strict identification and to deconvolute a complicated chromatogram.

Figure 44 :

 44 Figure 44: Comparison of MOMA ETU separation of pure chiral 3-methylhexane (top left) and in a laboratory test with a hand-held syringe injection to a COTS GC-MS (top right). Comparison of MOMA ETU separation of L-D-Serine (bottom left) and in a laboratory test with a hand-held syringe injection to a COTS GC-MS (bottom right). The m/z 43 ion is shown for 3-methylhexane and the m/z 70 ion is shown for Serine. For the ETU test, the GC column was held isothermally at 37˚C. For the laboratory test, the GC column was held at 35˚C for 7 min and then ramped to 182˚C at a ramp rate of 10˚C•min -1 . In this case, the time at the maximum trap temperature was taken as t0.

  [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF];[START_REF] He | Application of TMAH thermochemolysis to the detection of nucleobases: Application to the MOMA and SAM space experiment[END_REF] and Williams et al. (

Figure 55 :Figure 56 :

 5556 Figure 55: (Top) Chromatograms obtained using MTBSTFA direct derivatization in the presence of DMF. MTBSTFA/DMF heated at 250˚C for 3 min (black) and MTBSTFA/DMF derivatization performed directly on 5.23 mg of montmorillonite mineral (red). (1) Formamide, N,N,-dimethyl-(DMF), (2) tert-Butyldimethylsilanol (tBDMS), (3) N-(tert-butyldimethylsilyl)trifluoroacetamide, (4) Disiloxane, 1, 3-bis(1,1,[START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF] (5) phosphoric acid, 3tBDMS. (Bottom) Blanks of DMF-DMA. DMF-DMA was heated at 140˚C, 200˚C, or 250˚C for 3 minutes. The GC column was held at 40˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.0 mL•min -1 .

Figure 57 :

 57 Figure 57: Chromatographic response (peak area) compared between solvent extraction and direct derivatization across 5 wt. % samples of Mont+Glu, Mont+Phe, and Mont+PhA. As noted in the text, challenges for quantification of the peak area in the solvent extraction tests includes saturation of the chromatogram as well as derivatized pyroglutamic acid and glutamic acid peaks which are difficult to distinguish (for the Glu test). The quantity of moles sent to the GC column is ~2-4 nmol of each organic compound for solvent extraction and ~1 nmol for direct derivatization. This calculation considers the organic concentration of the sample, the amount (mg) of sample utilized for a test, dilution based on the derivatization reagent solution, and the split ratio of the GC.

Figure 62 :

 62 Figure 62: Chromatograms obtained from 200˚C, or 250˚C for 3 minutes) performed directly on montmorillonite samples doped with 5 wt. % and 1 wt. % of organics. Unless otherwise specified, chromatograms are displayed in XIC (m/z 163 for derivatized PhA, m/z 111 for derivatized Glu, and m/z 143 for derivatized Phe). For these 5 wt. % samples, the GC column was held at 40˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.0 mL•min -1 . The derivatives which are shown in this plot are L-glutamic acid, N-dimethylaminoethylene-(Glu), dimethyl ester, L-phenylalanine, Ndimethylaminomethylene-, methyl ester (Phe), and dimethyl phthalate (PhA). The structure of these molecules is shown in Figure64. *Marks the chromatographic peaks of L-glutamic acid, N-dimethylaminoethylene-.

Figure 63 :

 63 Figure63: Chromatograms obtained from 200˚C, or 250˚C for 3 minutes) performed directly on montmorillonite samples doped with 5 wt. % and 1 wt. % of organics. Unless otherwise specified, chromatograms are displayed in XIC (m/z 163 for derivatized PhA, m/z 111 for derivatized Glu, and m/z 143 for derivatized Phe). For these 1 wt. % samples, the GC column was held at 45˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.1 mL•min -1 . The derivatives which are shown in this plot are L-glutamic acid, N-dimethylaminoethylene-(Glu), dimethyl ester, L-phenylalanine, Ndimethylaminomethylene-, methyl ester (Phe), and dimethyl phthalate (PhA). The structure of these molecules is shown in Figure64. *Marks the chromatographic peaks of dimethyl phthalate.

Figure 64 :

 64 Figure 64: Chromatograms obtained from Phe, Glu and PhA standards at high concentration derivatized with DMF-DMA at 200˚C for 3 minutes. (1) dimethyl phthalate, (2) methyl-L-phenylalanine, N-dimethyl-, methyl ester, (3) Lglutamic acid, N-dimethylaminoethylene-, dimethyl ester, (4) possibly 2-methoxyethylmethyl phthalate, (5) N-formyl phenylalanine, methyl ester, (6) L-phenylalanine, N-dimethylaminomethylene-, methyl ester, (7) 5-ethoxy-2-phenyl-3H-imidazol-4-carboxylic acid, methyl ester. The GC column was held at 40˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.0 mL•min -1 .

Figure 65 :

 65 Figure 65: Relative efficiency of derivatization depending on the derivatization temperature. 15 µL of DMF-DMA was applied directly to ~10 mg of Mont+Phe, Mont+Glu, and Mont+PhA doped at 1 wt. % concentration. Samples were derivatized at 145˚C, 200˚C, or 250˚C for 3 minutes. IS = internal standard, which in this case is D8-naphthalene in DMF at 5×10 -3 M.

Figure 66 :

 66 Figure 66: Relative efficiency of derivatization depending on the derivatization temperature or duration. DMF-DMA derivatization of (Left) Mont+PhA, 5 wt. % samples in which the duration of derivatization was varied (45 seconds, 3 minutes, 5 minutes, and 10 minutes) and (right) Mont+Phe, 5 wt. % samples in which the derivatization temperature was varied (145˚C, 170˚C, 220˚C and 260˚C).

Figure 67 :

 67 Figure 67: Chromatograms obtained from TMAH thermochemolysis of 5 wt. % samples (5.2 mg of Mont+AMP 5 wt. %, 5.5 mg of Mont+Phe, 5 wt. %, 4.6 mg of Mont+Glu, 5 wt. % and 5.0 mg of Mont+PhA, 5 wt. %). (*) D8-Naphthalene (IS), (2) methenamine, (3) 9H-Purin-6-amine, N,9-dimethyl, (4) 9H-Purin-6-amine, N,N,9-trimethyl, (5) Toluene, (6) 3-aminoisobutyric acid, (7) Ethylbenzene, (8) Styrene, (9) Cumene, (10) Benzaldehyde, (11) Benzene, propenyl-, (12) Benzylnitrile, (13) Hydrocinnamic acid, methyl ester, (14) Cinnamic acid, methyl ester, (15) phenylalanine, N,N-dimethyl-, methyl ester, (16) Bibenzyl, (17)Propane 1, (18) Naphthalene, (19) Pyridine, 2, (20) phenol, 3-(dimethylamino)-, (21) L-glutamic acid, N,N,-dimethyl-, dimethyl ester, (22) L-proline,1-methyl-5-oxo-, methyl ester, (23) benzonitrile, (24) benzoic acid, methyl ester, (25) benzoic acid, (26) benzamide, N,N-dimethyl-, (27) biphenyl, (28) Phthalimide, N-methyl-(29) dimethyl phthalate, (30) N-methyl-1H-benzimidazol-2-amine, (31) fluorene, (32) benzophenone, (33) 9H-Fluoren-9-one. The GC column was a Supelco SLB-5MS (30 m x 0.25 mm x 0.25 µm). The GC column was held at 45˚C for 1 min and then ramped up to 300˚C at 10˚C•min -1 . The injector was set at 280°C. The He carrier gas flow rate was 1.1 mL•min -1 with a split ratio of 1/50.

Figure 70 :

 70 Figure 70: (Upper left) Mass spectra comparison between L-glutamic acid, 3tBDMS from test with Mont+Glu, 5 wt. % sample (MTBSTFA direct derivatization) and the NIST standard. (Upper right) Mass spectra comparison between L-glutamic acid, 3tBDMS from test with Mont+Glu, 0.1 wt. % sample (MTBSTFA direct derivatization) and the NIST standard. (Bottom left) Mass spectra comparison between L-glutamic acid, N-dimethylaminoethylene-, dimethyl ester from test with Mont+Glu, 5 wt. % sample (DMF-DMA direct derivatization) and the same L-glutamic acid chemical standard used to dope the montmorillonite samples. Both the chemical standard and the doped sample were derivatized with DMF-DMA at 200˚C for 3 minutes. (Bottom right) Mass spectra comparison of L-glutamic acid, N,Ndimethyl-, dimethyl ester from tests with Mont+Glu, 5 wt. % (TMAH) and SiO2+Glu, 5 wt. % (TMAH).

Figure 71 :

 71 Figure71: Chromatograms obtained from ramp pyrolysis of (left) 16.1 mg of montmorillonite and 17.7 mg of Mont+P and (right) 1 mg of pure Mg-perchlorate from the same batch which was used to dope the Mont samples. The GC column was held at 40˚C (7 minutes), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

Figure 72 :

 72 Figure 72: Chromatograms obtained from ramp pyrolysis of (top) 7.7 mg of Mont+AMP, 5 wt. % and (bottom) 8.8 mg of MontP+AMP, 5 wt. %. (1) CO2, (2) HCN, (3) acetonitrile, (4) column bleed, (5) HCl. The GC column was held at 40˚C (7 minutes), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

Figure 73 :

 73 Figure73: Chromatograms obtained from ramp pyrolysis of (top) 5.8 mg ofMont+Phe, 5 wt. % and (bottom) 8.1 mg of MontP+Phe, 5 wt. %. (1) CO2, (2) hydrogen cyanide, (3) acetonitrile, (4) benzene, (5) toluene, (6) ethylbenzene, dimethylbenzenes, (7) styrene, (8) ethylbenzenes, trimethylbenzenes, (9) propylbenzene, (10) benzene,1-ethnyl-3methyl, (11) benzonitrile, (12) indane; benzene,1-propynyl-; benzene, 3-pentenyl, (13) phenethylamine, (14) benzyl nitrile, (15) naphthalene, (16) benzenepropanitrile, (17) quinoline, (18) indole, (19) benzenebutanenitrile; quinoline,3-methyl; biphenyl, indolizine, methyl, (20) diphenylmethane, (21)1H-pyrrole, 2-phenyl; biphenyl, ethyl; (22) bibenzyl, (23) biphenyl, dimethyl; benzene, ethylbenzene; pentanone, methyl, diphenyl; (24) propane, diphenyl, (25) stilbene, (26) diphenylcyclopropane, (27) 1H-indene, 2-phenyl or anthracene, methyl, (28) 3-methyl-1-phenyl-1Hindene, (29) Benzeneethanamine, N-(phenylmethylene)-; 9H-Fluorene, 9-methylene-; 1H-indene, 1-(phenylmethylene)-, (30)1H-indene, 2-phenyl or anthracene, methyl (31) naphthalene, 2-phenyl-, (32) 2,6diphenylpyridine, (33) chlorobenzene, (34) benzofuran, (35) acetophenone, (36) dihydrobenzofuran. GC column: 40˚C (hold for 7 minutes), ramp to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

Figure 74 :

 74 Figure 74: Chromatograms resulting from the ramp pyrolysis of (top) 3.2 mg of MontP+PhA, 5 wt. % and (bottom) 11.4 mg of MontP+PhA, 1 wt. %. (1) CO2, (2) benzene, (3) column bleed, (4) chlorobenzene, (5) phenol, (6) three isomers of dichlorobenzene, (7) three isomers of trichlorobenzene, (8) benzoic acid, (9) phthalic acid, (10) biphenyl, (11) biphenyl, chloro-, (12) dibenzofuran, (13) benzophenone. TIC is in showed in black, and a reconstructed chromatogram with m112+m146+m180 is displayed in red. The GC column was held at 40˚C (7 minutes), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/10 and the helium flow is 1.0 mL•min -1 .

Figure 75 :

 75 Figure 75: Chromatograms obtained from MTBSTFA/DMF direct derivatization (250˚C, 3 min) of 5.40 mg of Mont+Glu, 5 wt. % and 5.81 mg of MontP+Glu, 5 wt. %. (1) pyroglutamic acid, 2tBDMS, (2) glutamic acid, 3tBDMS. The GC column was held at 40˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.0 mL•min -1 .

Figure 77 :

 77 Figure77: Chromatograms obtained from TMAH thermochemolysis of 5.5 mg of Mont+Phe, 5 wt. % (top) and 4.9 mg of MontP+Phe, 5 wt. % (bottom). (1) toluene, (2)3-aminoisobutyric acid, (3) chlorobenzene, (4) ethylbenzene, (5) styrene, (6) Cumene, (7) Benzaldehyde, (8) Benzene, propenyl-, (9) Benzylnitrile, (10) Hydrocinnamic acid, methyl ester, (11) Cinnamic acid, methyl ester, (12) phenylalanine, N,N-dimethyl-, methyl ester, (13) Bibenzyl, (14)Propane 1, (15) Naphthalene, 2-phenyl, (16) Pyridine, 2,6-diphenyl. The GC column was held at 45˚C (1 minute), then ramped to 300˚C at 10˚C•min -1 . The split ratio is 1/50 and the helium flow is 1.1 mL•min -1 .

Figure 78 :

 78 Figure 78: Categories of increasing complexity of the sample under testing as well as increasing or varying fidelity of the experimental setup to a flight experiment.

Figure 81 :

 81 Figure 81: Bird's eye view of homemade setup coupled to COTS GC-MS. Major components of the homemade online derivatization and trapping system linked to a COTS GC-MS are shown. The reactor is heated to 210-220˚C, the 6way valve is heated by the GC-MS Auxiliary function to 250˚C, the transfer line between the reactor and the 6-way valve and the transfer line between the 6-way valve and the Optic 4 injector are heated to about 100˚C. The Optic 4is used as either an injector or as a trap, in which case it is cooled to -30, -20, or 0˚C. In some tests, 30 mg of Tenax TA was added to the Optic 4 injector liner to aid with trapping. The injections of an alkane mixture described in this chapter were performed with a hand-held 0.5 µL Hamilton syringe and are injected to either the liquid inlet of the reactor which is lined with a custom-cut miniature septum or directly via the Optic 4 injector.V.3.Results and Discussion

Figure 82 :

 82 Figure 82: Handling of solid samples for online derivatization with homemade reactor setup.

  .g., 5 min) glutamic acid, identified in Atacama samples which were collected and analyzed by a variety of techniques, showed a concentration on the order of 1800 ng of glutamic acid per gram of sample.

Figure 83 :

 83 Figure 83: Chromatograms obtained from the direct MTBSTFA derivatization on ASAP Atacama Surface samples.(Top) 15 µL of an isopropanol and H2O solution(1:1) are applied directly on 6.29 mg of the sample and it is placed in an ultrasonic bath at a frequency of 38 kHz set at 60˚C for 1 h[START_REF] Buch | A new extraction technique for in situ analyses of amino and carboxylic acids on Mars by gas chromatography mass spectrometry[END_REF]. The solution was then left to evaporate under N2 flow for 30 min. Next, 10 µL of MTBSTFA/DMF(3:1) was added to the dried extract and underwent derivatization at 75˚C for 15 min. (Bottom) 6.02 mg of sample was sealed in a 5 mL ampule and was heated at 200˚C for 5 minutes. Next the sample was transferred to another 5 mL ampule and 9 µL of MTBSTFA/DMF(3:1) was added directly to the sample prior to undergoing derivatization at 170˚C for 10 minutes. 0.40 mg of sample was lost during the transfer of the sample from the thermodesorption step to the derivatization step. For the direct derivatization, 9 μL of MTBSTFA/DMF(3:1) was applied directly to about 6 mg of sample and sealed in a glass ampule. The sample was heated at 250 C for 3 min to allow the derivatization reaction to occur. In both tests, the derivatization was followed by GC-MS injection of 1 µL by hand-held 1 μL syringe (SGE). The GC column was an Agilent Chirasil Dex (30 m x 0.25 mm x 0.25 µm). The column had an initial temperature of 50˚C and a ramp to 190˚ at a rate of 3˚C•min -1 (Chirasil Dex). The flow rate was 1.0 mL•min -1 . The split ratio was 10:1 and the injection temperature was 280˚C. The mass scan range was m/z 10 to 550.

Figure 85 :

 85 Figure 85: MTBSTFA/DMF blanks under different conditions. The chromatograms are plotted as XIC, with m/z 313 and 341 plotted in each panel. (Top) MTBSTFA/DMF (4:1) blanks were derivatized offline at 75˚C for 15 minutes and at 250˚C for 3 minutes. 0.5 µL of the solution was injected to the GC by syringe (Bottom) A comparison of the sample test and the derivatization blank run as given in Figure 84.

Figure 86 :

 86 Figure86: Double, multiple, and wide peak behavior in homemade MOMA-like laboratory experimental setup. In each test, a mixture of 2-methylnonane, decane, and dodecane diluted in cyclohexane was injected on either the reactor or the Optic 4.(Top Left) Injection on the reactor and on the Optic 4 when the line between the 6-way valve and the Optic 4 was not yet heated. This test is not part of the nominal study, since the line was not yet heated, but is used here opportunistically in order to aid in the discussion of odd peak behavior in complex laboratory and space systems. (Top Right) Injection on reactor without Tenax TA present in Optic 4 liner and with the trapping temperature at -30˚C or -20˚C. (Bottom Left) Injection on reactor after 30 mg of Tenax TA has been added to the Optic 4 liner and before the Tenax TA has been conditioned at 280˚C for 24 hours. Again, this test is not part of the nominal study, since the Tenax was not yet fully conditioned, but is used here opportunistically in order to aid in the discussion of odd peak behavior in complex laboratory and space systems. (Bottom Right) Injection on reactor or on Optic 4 with Tenax TA present in the Optic 4 liner and with the trapping temperature at -20˚C or 0˚C. (1) 2-methylnonane, (2) decane, (3) dodecane, (4) decanal, (5) 1-decanol, (6) chlorinated straight-chain alkane. All plots are in XIC (m/z 57+71). It is not determined from where these compounds originate, if they are from contamination present in the lines or are produced by a reaction in the system.

  Figure 89. Additionally, there are occurrences of multiple (>2) peaks of the same compound appearing in runs in which the amount of injected species caused saturation of the column and/or the ion trap (Oddity 8). The examples of three peaks of both enantiomers of 2-pentanol (Blank 2 and Alcohol Mix 2) and at least ten additional peaks of hexadecanoic acid, methyl ester (Derivatization 2, Offline Derivatization) are shown in the top and middle panels of Figure 89.

Figure 87 :

 87 Figure 87: Comparison of peak area response of alkane mixture between an injection directly on the column through the Optic 4 inlet utilized as a conventional GC injector and an injection on the reactor via a syringe injection on the liquid inlet of the mini reactor. The error bars correspond to three repetitions of each test.

Figure 89 :

 89 Figure89: Odd peak behavior of injected compounds and trap degradation products in ETU data(Section III.2.3.1). (Top Left) Saturation of 2-pentanol (black) and enantiomeric separation of 2-pentanol in blank run after injection run (red). Multiple peaks of 2-pentanol are visible in the blank run after the injection(1, 2,[START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF]. (Top Right) Multiple peaks in first blank after alcohol mix injection.(1,2) 2-Butanol,[START_REF] Kobayashi | Global distribution, composition, and abundance of olivine on the surface of Mars from thermal infrared data[END_REF] (5,6) 2-Pentanol, (7) 2-Pentanol, (8) 2-Hexanol, (9) 2-Hexanol. (Middle Left) Multiple peaks in online derivatization run in which D-serine and decanoic acid are introduced to the ETU oven. *Potential additional peak of a methylated carboxylic acid. (Middle Right) Multiple peaks in which D-serine and decanoic acid are introduced to the system by syringe injection. Multiple peaks show a persistent contamination which probably comes from hexadecenoic acid, methyl ester. (Bottom Left) L-D-Serine (1,2), decanoic acid, methyl ester (3), and hexadecenoic acid, methyl ester (4). The RT of decanoic acid, methyl ester is shifted to a later retention time of 18.69 min. The solution underwent derivatization twice. (Bottom Right) Double peak of benzene coming from trap degradation. Tests performed on the MOMA Chirasil Dex column with a column temperature program of 40˚C (held for 3') ramped to 150˚C at a rate of 10˚C/min.

Figure 90 :

 90 Figure 90: Contamination control employed for testing of natural samples correlating to the protocol used for offline direct derivatization as shown in Section V.3.1.

Figure 91 :

 91 Figure 91: (Left) Amino acid signals seen in an MTBSTFA/DMF derivatization blank test (black curve) at similar levels as in a sample run (red curve). (Right) Amino acid signals seen at lower levels in a blank with no injection (black curve), MTBSTFA/DMF blank (red curve), an MTBSTFA/DMF blank + full solvent extraction handling without sample (blue curve), and the sample test (pink curve). This also shows how amino acids can be present in the instrument but not visible without a reagent blank. The extraction procedure in these tests was solvent extraction as illustrated in the top panel of Figure 80.

Figure 93 :

 93 Figure93: Flowchart of different experimental categories, including GC column, the injector system, the derivatization system, and the extraction technique which can have varying fidelities to the space experiment. "Column characteristics" includes the stationary phase, length, and internal diameter of the GC column.

V

  .R.a. Systematic study of MTBSTFA/DMF byproducts under the temperatures, durations and conditions of derivatization in flight. V.R.b. Efficiency of thermodesorption at relevant temperatures (for MOMA, e.g., ≤~200˚C prior to MTBSTFA derivatization) as an extraction technique for target molecules such as amino acids. Experimental testing of desorption efficiency of different types of amino acids (and other target compounds) from natural samples by varying the thermodesorption protocol within the constraints of the MOMA experiment. A characterization of the extraction efficiency of thermodesorption compared to solvent extraction may serve as a helpful test prior to conducting a systematic study of the thermodesorption protocol. V.R.c. Study of degradation products and product ratios from Tenax TA of MOMA IT traps with flight spare MOMA traps under MOMA operational conditions.

Table 1 :

 1 Oxidants detected or suggested to be present on Mars from review article by[START_REF] Lasne | Oxidants at the Surface of Mars: A Review in Light of Recent Exploration Results[END_REF]. *The Fe2O3 group includes hematite and maghemite; only hematite has been detected at the surface of Mars. **The clays studied to explain the Viking results were enriched with iron; the presence of this type of clay on Mars has not been confirmed yet.

	Group	Oxidant	Detected or Suggested	Origin
	Perchlorate salt	ClO4 -	Detected	Produced in the
				atmosphere
				Produced by UV
				irradiation of Cl-bearing
				minerals
	Iron-bearing species	• Fe2O3	• Detected*	• Thermodynamically
		• FeO4 2-	• Suggested	stable on Mars's
		• Clays	• Suggested**	surface • Minor phase
				(thermodynamically
				unstable)
				• Alteration of silicates
				in presence of water
	Reactive oxygenated	• Peroxide or	• Suggested	• Detection of species
	species	superoxide species	• Suggested	that could form
		• Superoxide radical ion		superoxides or
		(O2 -•)		peroxides
				• Formed in the
				presence of oxygen
				and UV radiation;
				formed with H2O2
	H2O2	• H2O2 in the atmosphere	• Detected	• Produced
		• H2O2 in the regolith	• Suggested	photochemically and
				during dust devils
				and storms
				• Produced by
				interaction between
				minerals and water

Table 3

 3

	: Evaluation of amino acid analytical techniques for spacecraft operation by Bada and McDonald (1996). 1
	= least suitable, 2 = suitable, 3 = most suitable.
	Criteria	GC-MS	HPLC	CE
	Sensitivity	1	3	3
	Analysis time	1	2	3
	Weight	2	1	3
	Mechanical complexity	1	1	3
	Reagent volume and storage	2	1	3
	Ease of derivatization	1	3	3
	Confirmation of peak identity	3	1	1
	Proven space worthiness	3	1	1
	Enantiomeric resolution	2	3	3
	Miniaturization potential	2	1	3
	Total score	18	17	26

Run ID Number Oven Temp Oven Purge Gas Time Column Held at 200˚C (min) Total Run Time (min)

	VL-1 Sample 1	10015	200	13 CO2	18	66
	Subsurface	10018	500	13 CO2	36	48
	VL-1 Sample 2 Surface	10023 10024 10025	350 500 500	13 CO2 13 CO2 13 CO2	54 54 36	66 84 84
	VL-2 Sample 1 Bonneville Duracrust	10032 10033 10034 10035	200 350 500 500	H2 H2 H2 13 CO2	36 36 36 36	66 66 66 66
		10036	50	H2	36	66
	VL-2 Sample 2	10037	200	H2	36	66
	Under Badger	10038	350	H2	36	66
	Rock	10039	500	H2	36	66
		10041	500	13 CO2	36	66

Table 5 :

 5 A comparison between the abundance of dichloromethane a and chlorobenzene b detected in VL-2 samples with temperature. Note: values are in parts per billion by mass (ppbm) for 100 mg samples. Numbers in parentheses indicate the approximate scan numbers where components elute. ND = not detected.

		Oven		Acetone	Benzene	Toluene	Xylene	DCM	CBZ
	Sample	Temp,	Mode	(92)	(129)	(140)	(150)	(89)	(148)
		ºC		(ppbm)	(ppbm)	(ppbm)	(ppbm)	(ppbm)	(ppbm)
	Blank	500	CO2	120-240 a	4-8 a	1-2 a	0.6-1.4 a	ND	ND
		200	H2	60-120 a	1-2 a	2-3 a	0.3-0.5 a	ND	ND
	Bonneville	350 500	H2 H2	40-70 a 10-20 a	3-6 a 3-6 a	2-3 a 0.8-1.6 a	0.3-0.5 a 0.4-0.8 a	6-14 a 6-14 a	>0.1 >0.5
		500	CO2	1-2 a	2-4 a	0.6-1.4 a	1-3 a	2-6 a	ND
		50	H2	ND	0.2-0.4 a	0.1-0.3 a	ND	ND	ND
	Under Badger	200	H2	200-400 a	0.6-1.4 a	0.4-0.8 a	0.3-0.5 a	0.04-0.08 a	ND
	Rock	350	H2	30-60 a	0.6-1.4 a	0.3-0.5 a	ND	10-20 a	>0.08
		500	H2	<5 a	1-2 a	0.04-0.08 a	ND	<4 a	>0.2
		500	CO2	5-10 a	0.75-1.75 a	1-1.5 a	0.1-0.2 a	20-40 a	>0.7

a Biemann et al. 1977. b

This study.

Table 6 :

 6 List of chemical standards tested on GC columns. The derivatization reagents cited in the last column were used for each of the GC columns listed in the corresponding first column. *Alcohols were not derivatized for studying the MXT Q BOND column since the underivatized alcohols had already sufficiently high retention times within the nominal 35-min run time.

	Column	Family	Chemical Standard	Solvent and Concentration	Derivatization Agent
					Alcohols	C2 to C9 linear alcohols	10 -4 vol% in methanol (for non-derivatized alcohols)	Tests were conducted with no derivatization and with derivatization (DMF-DMA, MTBSTFA/DMF)
					Alkanes	C7 to C40 linear and ramified alkanes	1 g•L -1 in hexane	N/A
	CP Chirasil Dex	MXT-5	MXT-CLP	Carboxylic acids	Oxalic acid Dodecanoic acid Benzoic acid Hexanoic acid Octanoic acid Nonanoic acid Decanoic acid	10 -2 mol•L -1 in demineralized water	Carboxylic acids were derivatized with DMF-DMA and MTBSTFA/DMF
						Mellitic acid
						Glycine
						DL-alanine		Amino acids were derivatized
					Amino acids	DL-valine DL-glutamic acid	10 -2 mol•L -1 in demineralized water	with DMF-DMA
						DL-serine		and MTBSTFA/DMF
						DL-leucine
	CP Chirasil	Dex	Alkanes	3-methylhexane, 3-methylheptane	10 -3 vol. % in cyclohexane	N/A
					Alcohols	C2 to C5 linear alcohols	10 -4 vol. % methanol	N/A*
		MXT Q BOND		Noble Gases Hydrocarbons	Neon, Argon, Krypton, Xenon Ethane, Ethylene, Butane, Pentane	15 mol. %, 5 mol. %, 3 mol. %, 2 mol. % in helium 0.0095675% (butane), 0.0099951% (pentane) in helium; concentration for	N/A N/A
							ethane and ethylene
							not available

Table 7 :

 7 List of GC capillary columns selected for MOMA GC and their main characteristics.

	Name (Supplier)	Stationary Phase	Dimensions L/ID/df (m/mm/µm)	Compounds targeted
				Inorganic volatile
	MXT Q BOND (Restek)	Divinylbenzene	20/0.25/8	molecules C1-C5 organic
				molecules
	MXT CLP (Restek)	Not available from the supplier	20/0.25/0.25	C4-C25 organic molecules
	MXT 5 (Restek)	95% dimethylsiloxane 5% diphenylsiloxane	20/0.25/0.25	C4-C25 organic molecules
		Enantioselective,
	CP Chirasil Dex CB (Agilent)	b-cyclodextrin bonded to	20/0.25/0.25	Organic enantiomers
		dimethylpolysiloxane

  .

	Experimental component	Parameter	Flight Model	Laboratory GC-MS
				Optimized temperatures
		Tmax derivatization oven (˚C)	600	for standards (75˚C for MTBSTFA; 140˚C for
	Ovens, transfer lines, and			DMF-DMA)
	trap	Tmax transfer lines (˚C)	≥135	250 (GC-MS transfer line)
		Tmax trap (˚C)	300	No trap
		Trap flow mode	Supports flow inversion	No flow inversion
		Ti (˚C)	≥30	35-45
		Ramp rate (˚C•min -1 )	1-15	3-10
			220˚C (MXT 5, MXT	220˚C (MXT 5, MXT
	GC	Tf (˚C)	CLP) 180˚C (Chirasil Dex)	CLP) 180˚C (Chirasil Dex)
			200˚C (Q BOND)	200˚C (Q BOND)
			0.8 to 1.4 mL•min -1
		He flow rate (mL•min -1 )	(adjustability); 1.2	0.2 to 2 mL•min -1
			mL•min -1 (nominal)
	MS	Mass range (m/z)	50-500	10-500

Figure 25: Comparison of main column temperature programs used for characterization of the MOMA GC columns in a laboratory setting. The nominal MOMA temperature curves used for the study of chemical standards on each of the four columns (MXT 5/CLP, MXT Q BOND, and CP Chirasil Dex CB) are given, as well as the temperature program used for the study of enantiomeric resolution of chiral compounds on the MOMA chiral column, which was meant to mimic the ETU tests.

Table 9 :

 9 Nature of samples, preparation methods, and mode of injection used for 2018 GSFC ETU GC-MS coupling campaign.

	TID	Sample/solution	Pyrolysis/Derivatization	Injection
	8407	Blank	No	Blank injection
	8408	2-pentanol	No	0.1 µL by syringe
	8409	Blank #2	No	Blank injection
	8413	2-butanol, 2-pentanol, 2-	No	Headspace of vial
		hexanol
	8418	3-methylhexane	No	Headspace of vial
	8419	10 µL D-Ser (10 -1 M), 10	30 µL DMF-DMA, offline	0.1 µL injected to oven
		µL L-Ser (10 -1 M)		at 250˚C
	8420	50 µL each of D-Ser, L-	30 µL DMF-DMA, offline	0.1 µL injected to oven
		Ser, palmitic acid,		at 250˚C
		decanoic acid
	8422	0.2 µL of solution used	DMF-DMA, online	0.2 µL
		for TID 8420	Derivatization performed twice
	8424	Blank #3	No	No injection
	8425	DMF-DMA Blank	DMF-DMA, online	0.2 µL
	8426	D-Ser, L-Ser, palmitic	0.4 µL DMF-DMA, online	Solution deposited on
		acid, decanoic acid		Al foil
	8428	D-Ser, decanoic acid	0.5 µL DMF-DMA, online	Solution deposited on
				Al foil
	8429	D-Ser, decanoic acid	0.2 µL DMF-DMA, offline	Injected directly to oven

Table 10 :

 10 Column details for GSFC ETU tests with chemical standards, presenting the MOMA GC column used for the separation and its operating temperature program. For all these tests, the helium flow rate was maintained at ~1.2 mL•min -1 in the column.

		Test Info		Column
	Campaign	TID Ref. #	Test Description	Column	Column T program
		8407	Blank	Chirasil	40˚C (3.4') ramp to 165˚C (no hold), 9.8˚C•min -1
		8408	Alcohols	Chirasil	40˚C (3') to 150˚C, 10˚C•min -1
		8409	Blank 2	Chirasil	40˚C (3') to 180˚C; 8.8˚C•min -1
		8413		Chirasil	40˚C (3') to 180˚C; 8.8˚C•min -1
	GSFC ETU 2018	8418 8419 8420	Methylhexane Amino Acids Amino Acids 2	Chirasil Chirasil Chirasil	37˚C isothermal 40˚C (3') to 180˚C; 9.0˚C•min -1 40˚C (3') to 180˚C (9' hold); 9.0˚C•min -1
		8422	Amino Acid Mix	Chirasil	40˚C (3') to 180˚C (8' hold); 9.0˚C•min -1
		8424	Blank	Chirasil	40˚C (3') to 180˚C (15' hold); 9.0˚C•min -1
		8425	DMF-DMA Blank Chirasil	40˚C (3') to 180˚C (11' hold); 9.0˚C•min -1
		8426	Derivatization 1	Chirasil	40˚C (3.4') to 180˚C (10.5' hold); 9.0˚C•min -1
		8428	Derivatization 2	Chirasil	40˚C (3.3') to 180˚C (15.6' hold), 9.0˚C•min -1

Table 11 :

 11 Summary of values related to the efficiency of the spare MOMA GC columns. The minimum HETP is in cm and the optimal carrier gas velocity is in cm•s -1 .

		0.065	MXT CLP (115˚C)							0.09	MXT CLP (60˚C)
		0.060											0.08			y˚=˚1.10˚-˚0.0432x˚+˚0.000446x 2
		0.055		y˚=˚0.669˚-˚0.0266x˚+˚0.000278x 2				0.07			y˚=˚2.96˚-˚0.118x˚+˚0.0012x 2
	HETP˚(cm)	0.045 0.050			˚DL-Alanine ˚Poly.˚(DL-Alanine)				HETP˚(cm)	0.06
		0.040											0.05
														˚Butanol-1
		0.035												˚CBZ
		0.030					! " minimum					0.04	˚Poly.˚(CBZ) ˚Poly.˚(Butanol-1)	! " minimum	! " minimum
			40	42	44	46	48	50	52	54	56	58		42	44	46	48	50	52	54
					He˚velocity˚(cm.s	-1 )							He˚velocity˚(cm.s -1 )
		0.09	MXT CLP (120˚C)							0.12	MXT Q BOND (115˚C)
					y˚=˚0.834˚-˚0.0315x˚+˚0.000320x 2
		0.08			y˚=˚1.04˚-˚0.0434x˚+˚0.000476x 2				0.11
		0.07
													0.10			y˚=˚0.222˚-˚0.00473x˚+˚0.0000396x 2
	HETP˚(cm)	0.05 0.06										HETP˚(cm)	0.09				˚Ethanol-1 ˚Poly.˚(Ethanol-1)
									! " minimum
		0.03 0.04			! " minimum			˚Butanol-1 ˚CBZ ˚Poly.˚(CBZ) ˚Poly.˚(Butanol-1)		0.08				! " minimum
													0.07
			40	42	44	46	48	50	52		54	35	40	45	50	55	60	65	70	75
					He˚velocity˚(cm.s -1 )							He˚velocity˚(cm.s -1 )
	Efficiency values		MXT Q BOND 115˚C		MXT CLP 60°C 115/120°C	60°C	MXT 5 115/120°C	CP Chirasil Dex 60°C 115/120°C
		H (cm)		0.08			0.05-0.06		0.03-0.06	0.04-0.05		0.04-0.07	0.06-0.14	0.05
	$ %opt (cm•s -1 )			60			48-49		46-49		48-51		49-53	61-67	55-61

Figure

32

: Noble gases separated on the MXT Q BOND. The GC column was held at 35˚C for 7 min, then heated to 182˚C with a 3˚C•min -1 ramp. The Ar response is high compared to the other noble gases, considering the relative ratios of the gases, because Ar was mixed with some air (N2 and O2) that entered the syringe before injection.

  MTBSTFA) results in a lower molecular weight of the final molecule after derivatization, which means a greater chance of it eluting during the 35-minute run.

1,2,4-benzenetricarboxylic acid, trimethyl ester and 1,2-benzenedicarboxylic acid bis(2-methylpropyl) ester. It is easier to detect partially derivatized mellitic acid with DMF-DMA in comparison with MTBSTFA, because adding a methyl group to the molecule (DMF-DMA) in comparison to a tert-butyldimethylsilyl group (Figure 34: A comparison of the separation capabilities of derivatized and non-derivatized alcohols on the MXT CLP and MXT Q BOND capillary columns. (Top) pure alcohols, MXT CLP, (Middle) MTBSTFA-derivatized alcohols, MXT CLP, and (Bottom) pure alcohols, MXT Q BOND. (

1

) ethanol, (2) 1-propanol, (3) 1-butanol, (4) 1-pentanol, (5) 1-hexanol, (6) 1-heptanol, (7) 1-octanol, (8)1-nonanol, (9) 1-undecanol. Although marked with the same numbering system, note that in the case of the middle panel, molecules are MTBSTFA-derivatized alcohols. The GC column was heated from 45˚C to 220˚C (MXT CLP) or 200˚C (Q BOND) with a 10˚C•min -1 ramp and held for a total run time of 35 min.

Table 12 :

 12 Retention times of selected compounds on the Chirasil Dex, MXT 5, and MXT CLP columns. The measured dead times were between 0.63-0.70 min (MXT 5), 0.69-0.76 (MXT CLP), and 0.61-0.63 (Chirasil Dex). *Shows a comparison between retention times with a dead time of 0.69 vs. 0.63 min. **Less robust mass spectra assignment.

	Family	Compound Reference Number	Compound	Chirasil Dex	MXT 5	MXT CLP
		1	1-Propanol-1, pure	1.53	0.84	0.95
		2	1-Butanol, pure	2.91	1.03	1.19
		3	1-Pentanol, pure	4.48	1.46	1.68
		4	1-Hexanol, pure	5.78	2.24	2.48
		5	1-Heptanol, pure	6.91	3.32	3.59
		6	1-Octanol, pure	8.03	4.64	4.87
		7	1-Propanol, DMF-DMA derivative	3.96	2.53	2.41
	Alcohols	8 9 10 11	1-Butanol, DMF-DMA derivative 1-Pentanol, DMF-DMA derivative 1-Hexanol, DMF-DMA derivative 1-Heptanol, DMF-DMA derivative	5.12 6.43 7.73 8.97	3.63 4.92 6.22 7.54	3.40 4.57 5.82 7.06
		12	1-Octanol, DMF-DMA derivative	10.16	8.77	8.27
		13	1-Propanol, tBDMS	6.49	2.66	2.62
		14	1-Butanol, tBDMS	7.79	3.78	3.55
		15	1-Pentanol, tBDMS	9.00	4.98	4.76
		16	1-Hexanol, tBDMS	10.15	6.29	5.98
		17	1-Heptanol, tBDMS	11.27	7.58	7.21
		18	1-Octanol-1, tBDMS	13.52	8.82	8.42
		19	Heptane (C7)	1.66	1.10	0.97
	Alkanes	20	Octane (C8)	2.60	1.61	1.36
		21	Nonane (C9)	3.85	2.47	2.05

Table 13 :

 13 Retention times for selected compounds on the MXT Q BOND column. The measured dead time was ~0.55 min. *The ETU temperature program was used.

	Family	Compound Reference Number	Compound	Q-PLOT
		1	1-Propanol	10.11
		2	1-Butanol	13.02
	Alcohols	3	1-Pentanol	15.61
	(pure)	4	1-Hexanol	19.09
		5	1-Heptanol	26.21
		6	1-Octanol	41.56
		66	Neon	0.85*
	Noble Gases	67	Argon	0.89*
	(pure)	68	Krypton	0.98*
		69	Xenon	1.69*
		70	Ethane	1.13
	Hydrocarbons	71	Ethylene	0.95
	(pure)	72	Butane	6.38
		73	Pentane	9.61
	lower on SAM (~0.8 mL•min

-1

) than on MOMA (~1.2 mL•min

-1

Table 14 :

 14 Retention times and the temperature at which the retention time occurs on each Chirasil Dex column for each of the molecules in the laboratory COTS GC-MS versus on the MOMA ETU. The retention time is taken with the start of the trap heating as t0. The range in retention time for L-, D-Serine, decanoic acid, methyl ester, and hexadecanoic acid, methyl ester corresponds to a slight difference in initial isothermal hold of the GC column temperature depending on the run and/or slight differences in the injection conditions. *There is one case(TID Ref. #8422) in which the retention time of decanoic acid, methyl ester is shifted later in the run to 18.69 minutes. This case is discussed in Chapter V, Section V.4.2.2.

	Molecule	ETU		Laboratory
		R_T (min)	T (˚C)	R_T (min)	T (˚C)
	2-Butanol	4.39, 4.52	51, 52	3.71, 3.95	During 7' hold at
					35˚C
	2-Pentanol	6.82, 6.89	75, 76	9.33, 9.52	58, 60
	2-Hexanol	8.63	94	11.78, 11.86	83, 84
	3-Methylhexane	3.37	Isothermal	2.36	Isothermal hold at
			hold at 37˚C		35˚C
	L-Serine	11.01-11.40	~113	14.79	113
	D-Serine	11.26-11.65	~117	15.12	116
	Decanoic acid, methyl	13.78-14.09*	~138	17.69	142
	ester
	Hexadecanoic acid,	22.42-22.85	During final	19.90	During final
	methyl ester		isothermal		isothermal hold at
			hold at ~180˚C		182˚C

Table 16 :

 16 Samples of Montmorillonite SAz-1 mineral doped with four compounds, adenosine 5'-monophosphate (AMP), L-Glutamic acid (Glu), L-Phenylalanine (Phe), and Phthalic Acid (PhA) which were used for GC-MS analyses. Blank samples of cleaned montmorillonite and montmorillonite treated with perchlorate were also provided as well as chemical standards of the AMP, Glu, Phe, and PhA used. Montmorillonite samples doped with a mixture of all four organic compounds at each of the concentration levels(5, 1, 0.1 wt. %) were also provided to the team, but were not heavily tested to decrease the complexity of the analysis.

	Sample Description	Sample Shorthand Name	Organic Concentration
			(wt. %)
	Pure montmorillonite Saz-1	Mont	N/A
	Pure montmorillonite Saz-1 treated with	MontP
	Mg-perchlorate (1 wt. %)
	Adenosine 5'-monophosphate	AMP
	L-glutamic acid	Glu
	L-phenylalanine	Phe
	Phthalic acid	PhA
	Montmorillonite SAz-1 doped with AMP	Mont+AMP, 5 wt. %	5
		Mont+AMP, 1 wt. %	1
		Mont+AMP, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with AMP	MontP+AMP, 5 wt. %	5
	and treated with Mg-perchlorate (1 wt. %)	MontP+AMP, 1 wt. %	1
		MontP+AMP, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with Glu	Mont+Glu, 5 wt. %	5
		Mont+Glu, 1 wt. %	1
		Mont+Glu, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with Glu and	MontP+Glu, 5 wt. %	5
	treated with Mg-perchlorate (1 wt. %)	MontP+Glu, 1 wt. %	1
		MontP+Glu, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with Phe	Mont+Phe, 5 wt. %	5
		Mont+Phe, 1 wt. %	1
		Mont+Phe, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with Phe and	MontP+Phe, 5 wt. %	5
	treated with Mg-perchlorate (1 wt. %)	MontP+Phe, 1 wt. %	1
		MontP+Phe, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with PhA	Mont+PhA, 5 wt. %	5
		Mont+PhA, 1 wt. %	1
		Mont+PhA, 0.1 wt. %	0.1
	Montmorillonite SAz-1 doped with PhA	MontP+PhA, 5 wt. %	5
	and treated with Mg-perchlorate (1 wt. %)	MontP+PhA, 1 wt. %	1
		MontP+PhA, 0.1 wt. %	0.1

  Section IV.3.2.2.2), and chromatographic response across organic concentration of samples (Section IV.3.2.2.3). The DMF-DMA results and discussion cover DMF-DMA derivatives (Section IV.3.2.3.1) and some testing of the effect of modifications to the DMF-DMA protocol (Section IV.3.2.3.2). The TMAH results results and discussion cover thermolysate identifications and proposed formation paths (Section IV.3.2.4).

	solvent extraction and direct derivatization of samples (Section IV.3.2.2.1), MTBSTFA
	derivatives (
	Intensity (cps)	1.0x10 9 2.0x10 9	1	2	3	4	5	6	9 7	8	11 10 12	14 15 16 13 17 18 19 18 20	Flash Pyrolysis 26 28 22 29 27 24 25 23 21
		0.0
					5						10		15	20
	Intensity (cps)	1.0x10 9 2.0x10 9	1		3			6			12	16 14	18 19	21	Ramp Pyrolysis 23 22
		0.0
				10					15			20		25	30
											Time (min)

3.2.1)

. Next, the MTBSTFA (Section IV.3.2.2) and DMF-DMA (Section IV.3.2.3) derivatization and TMAH thermochemolysis (Section IV.3.2.4) results for the doped montmorillonite samples are discussed. The MTBSTFA results and discussion cover

Table 21 :

 21 Theoretical limit of detection and limit of quantification of the separated organic compounds derivatized with MTBSTFA in the presence of DMF.

	Sample	Compound	Quantity to GC (nmol)	LOD (nmol)	LOQ (nmol)
	Mont+Glu	Glutamic acid, 3tBDMS	0.029-1.14	0.0922	0.280
	Mont+Phe	Phenylalanine, 2tBDMS	0.025-1.19	0.0112	0.0338
	Mont+PhA	Phthalic acid, 2tBDMS	0.029-1.02	0.0241	0.0730

Table 23 :

 23 Summary of detections of organic compounds or their derivatives enabled by the GC-MS analysis in this chapter. (+) denotes detection of pristine organic compound (AMP, PhA, Phe, or Glu), ( †) a derivatized molecule or directly methylated molecule (TMAH), and ( ‡) thermal degradation products or rearranged molecules. This table refers to results with the 5 wt. % samples since these samples were tested across all GC-MS techniques (pyrolysis, derivatization, and thermochemolysis). *It is not determined if pyroglutamic acid is present in the sample prior to derivatization.

Table 24 :

 24 Comparison of chromatographic response across chemical reagents. CR = Chromatographic response.

	Sample	Chemical	Compound	To GC	CR (cps•min)	A/AIS	CR per
		Reagent		(nmol)			nmol
	Mont+	MTBSTFA	L-glutamic acid,	1.14	1.89E+09 ± 1.99E+08	No IS	1.66E+
	Glu, 5 wt.		3tBDMS				09
	%	DMF-DMA	L-glutamic acid, N-	0.96	5.01E+07	0.31	5.22E+
		(250˚C)	dimethylaminomethyl				07
			ene-, dimethyl ester
		TMAH	L-glutamic acid,	31	3.92E+08	0.16	1.26E+
			N,N,-dimethyl-,				07
			dimethyl ester
	Mont+	MTBSTFA	L-phenylalanine,	1.17	3.83E+09 ± 8.73E+07 No IS	3.27E+
	Phe, 5 wt.		2tBDMS				09
	%	DMF-DMA	Phenylalanine, N-	1.00	7.59E+08	8.25	7.59E+
		(200˚C)	dimethylaminomethyl				08
		DMF-DMA	ene-methyl ester	1.70	3.02E+09	53.94	1.78E+
		(250˚C)					09
		TMAH	Pyridine, 2,6-	33	2.85E+09	1.08	8.64E+
			diphenyl				07
			Phenylalanine, N,N-		1.39E+09	0.53	4.21E+
			dimethyl-, methyl				07
			ester
	Mont+	MTBSTFA	Phthalic acid,	1.00	4.20E+09 ± 3.53E+08	No IS	4.20E+
	PhA, 5		2tBDMS				09
	wt. %
		DMF-DMA	Dimethyl phthalate	2.55	4.71E+08	3.60	1.85E+
		(200˚C)					08
		DMF-DMA		1.86	6.57E+08	11.15	3.53E+
		(250˚C)					08
		TMAH	Benzoic acid, methyl	31	8.29E+09	4.06	2.67E+
			ester				08
			Phthalimide, N-		6.41E+09	3.14	2.07E+
			methyl				08
			Dimethyl phthalate		4.59E+09	2.25	1.48E+
							08
	Mont+	MTBSTFA	Phthalic acid,	0.28	1.45E+09 ± 7.22E+07	No IS	5.18E+
	PhA, 1		2tBDMS				09
	wt. %
		TMAH	Benzoic acid, methyl	5.60	7.27E+08 ± 6.00E+07 0.23	1.30E+
			ester				08
			Phthalimide, N-		3.50E+09 ± 1.97E+08 0.29	6.25E+
			methyl				08
			Dimethyl phthalate		3.30E+07 ± 2.12E+07 0.0046	5.90E+
							06
	Mont+	MTBSTFA	Phthalic acid,	0.029	1.96E+06 ± 3.09E+05 No IS	6.76E+
	PhA, 0.1		2tBDMS				07
	wt. %
		TMAH	Benzoic acid, methyl	0.63	2.65E+07	0.01	4.21E+
			ester				07
			Phthalimide, N-		6.49E+07	0.025	1.03E+
			methyl				08
			Dimethyl phthalate		Below LOQ

Figure

69

: Chromatographic response (cps•min) of organic derivatives per nanomole of organic parent molecule sent to GC for experiments across the three chemical reagents that will be utilized on MOMA

(MTBSTFA, DMF-DMA, and TMAH)

. These units are used for the comparison in order to account for the higher quantity of organic derivative sent to the GC column in the thermochemolysis experiments in comparison to the derivatization experiments. Even if multiple derivatives can arise from a single parent molecule, the derivatives that are quantified in this plot are Lglutamic acid, 3tBDMS; L-phenylalanine, 2tBDMS; and phthalic acid, 2tBDMS (from the MTBSTFA derivatization reaction); L-glutamic acid, N-dimethylaminomethylene-, dimethyl ester; phenylalanine, N-dimethylaminomethylenemethyl ester; and dimethyl phthalate (from the DMF-DMA derivatization reaction); and L-glutamic acid, N,N,dimethyl-, dimethyl ester; phenylalanine, N,N-dimethyl-, methyl ester; and dimethyl phthalate (from the TMAH thermochemolysis reaction). (Left) Results from MTBSTFA/DMF derivatization experiments with Mont+Glu, Mont+Phe, and Mont+PhA samples across the three concentrations (5 wt. %, 1 wt. %, and 0.1 wt. %). (Middle) Results from DMF-DMA derivatization experiments with Mont+Glu, Mont+Phe, and Mont+PhA samples at 5 wt. % at two different temperatures

(200˚C and 250˚C)

. (Right) Results from TMAH thermochemolysis experiments with Mont+Glu, Mont+Phe, and Mont+PhA samples at 5 wt. % and Mont+PhA at 1 wt. %. Mont+PhA at 0.1 wt. % was also tested, but the directly methylated product of phthalic acid, dimethyl phthalate, was below the limit of quantification.

  3.2.1 and IV.3.2.4) i. TMAH thermochemolysis enables detection of methylated products of all four organic compounds (AMP, Glu, Phe, PhA) as well as additional thermolysates, for which formation mechanisms are proposed. IV.d. Comparative analysis of GC-MS sub-modes (Section IV.3.3) i. The combination of pyrolysis-GC-MS, MTBSTFA and DMF-DMA derivatization GC-MS, and TMAH thermochemolysis GC-MS represents the analytical GC-MS capabilities of the MOMA experiment. The GC-MS package enables detection of each target organic molecule or its products in the presence of a clay mineral across multiple sub-modes (Table

  , likely the highest yield for amino acids of those reagents utilized in space experiments (i.e., MTBSTFA, DMF-DMA, TMAH). Since MTBSTFA has a higher yield for derivatized amino acids than DMF-DMA and TMAH, MTBSTFA is often discussed in reference to space experiments as the first pass reagent for targeting the detection of amino acids present in a sample. Only if amino acids are detected by MTBSTFA derivatization, will a second experiment be run with DMF-DMA, which although amino acid responses are lower with DMF-DMA, DMF-DMA can enable enantiomeric separation of chiral molecules (Chapter III, Section III.3.3).

  Table 25 is a reference table of those experiments and experimental details of studies specifically for application to space experiments with the intention of easily being able to link sample complexity and experimental setup fidelity to space experiments such as SAM and MOMA within discussions of a demonstrated laboratory detection of amino acids and their relevance for a given space experiment.

Table 25 :

 25 Demonstrated detection of amino acids by MTBSTFA derivatization + GC-MS for planetary science across varying complexity of samples and fidelities of experimental setups to the space experiment.

  Detection of amino acids in martian samples requires extraction from the mineral matrix and efficient derivatization to enable detectability by GC-MS. Additionally, specific components of the space experiment can have implications for the extraction and/or derivatization step and decrease or increase detection limits compared to traditional tests in the laboratory in which derivatization is performed on amino acid chemical standards or solvent extracts using COTS instrumentation.

	Brault 2015 Meunier et al. 2007 Buch et al. 2003 Siljeström et al. 2014 Morisson et al. 2017 David et al. 2016 Buch et al. 2006 Fidelity of space-like laboratory-based experimental setups Buch et al. 2009 Stalport et al. 2012 Bishop et al. 2013 V.1.3.	Study Study
	Chemical standards, spiked Spiked natural sample & natural sample Chemical standards Spiked natural sample (cleaned of & natural samples Spiked mineral, natural Spiked natural sample samples Natural samples Natural samples Natural samples Natural sample	Classification of sample under Classification of sample under
																				organic traces)	natural samples	testing testing
	17 AA Spiked Fontainbleau soil (6 AA) and non-spiked Atacama soil Lake Hoare E2, Colletthøgda (Snickers, Gly, Ser, Glu Ala, Gly, Ser, Glu on Fontainbleau soil standards; garden soil and Atacama Chemical standards, Atacama sample spiked with 14 AA pseudomonas fluorescens strain and Atacama Atacama-01/02, JCS Mars-1, Río Tinto-01, Carbonate-01, bottom, oxic Botnia E3, E4 -lake KitKat, Butterfinger), JSC Mars-1	Compounds or Sample Compounds or Sample
	Mu hi	(USNM																	i	H3 lak
	100 mg		Depends on experiment 1.5 g (solvent) to 500 mg (one-pot/one-step) 100 mg (online in 25 g (extraction solvent tests), 1 g (LOD) reactor bed) 50 mg sample (online) 0.5 g Atacama 47-52 mg 10-20 mg (campaign), 80-190 mg (lab) 20 mg JSC Mars-1	Quantity Quantity
		N/A	8×10 -7 mol/g Varied for calibration 2.5 to 250 nmol of each AA 0.1 ppm (on solid sample) (spiked) N/A	Depends on experiment N/A	10 -6 mol/g (spiked) N/A	Concentration Concentration
	Pyrene, 3-FV			Pyrene				None	Anthracene D8-naphthalene	None	Methyl-laurate None	Pyrene Pyrene; 3-fluoro-DL-valine	IS IS
	sonification extraction/derivatizat One-pot ion at 300˚C for several minutes	with	derivatization	extraction /	N/A spiked) Direct offline derivatization Solvent extraction + sonification (some cases) for 5 min (spiked) 500˚C for 5 min (non-Online derivatization and solvent extraction + sonification (campaign), solvent Solvent extraction + (1) Solvent Offline derivatization One-pot/one-step online extraction + extraction/ sonification, derivatization (2) one-step derivatization (lab) extraction + offline sonification	Solvent + extraction/derivatiz sonification; one-pot/one-step spiked, non-spiked samples -thermodesorp tion at 300˚C One-pot 3 min ation at 300˚C for	Organic extraction technique Organic extraction technique
	Fused silica quartz glass powder for				Interaction between reagent & Dried at 110˚C, 36h Fontainebleau cleaned of organic and sieved (1-mm 48 h incubation at 25°C, N/A colonies scraped off, N/A N/A	N/A	N/A	Other Other
	blank heated to			soil observed gauge) garden soil traces by sulfuric suspended in ultrapure water
	Thermo Scientific Trace GC + DSQ II Shimadzu GC-MS, quadruple detection mode Varian Saturn 2 Shimadzu QP5050 GC-MS GC-MS Shimadzu QP5050 GC-MS Thermo Finnigan Trace GC Ultra/Trace DSQ Pyroprobe interfaced to Thermo-Finnigan Trace GC + DSQ quadrupole MS " Similar to" Thermo DSQII GC/MS Griffin Minotaur 400 field GC-MS (campaign) Thermo Finnigan Trace GC Ultra ThermoScientific DSQII MS Trace GC Ultra-ISQ (lab) LT	GC-MS Experimental Setup GC-MS Experimental Setup
	coupled to gas
	30 m Restek RTX 5 MS	30 m ZB-5MSi Depends on experiment 30 m Restek RTX-1 15 m CPSIL 5 CB 30 m Restek RXi-5Sil 15 m RTX 5ms 30 m Rxi-5 30 m Restek Rxi-20 m MXT20 5Sil SM	GC Column GC Column
	SAM-like hydrocarbon trap assembly		injector	N/A COTS GC	of the	septum	into the	inserted	reactor)	Outlet None transfer (online	N/A	N/A Used only for pyrolysis Not specified tests	sieve	N/A TA and Carbo-	Tenax	beads,	of glass	like trap	SAM-	Injection Trap Injection Trap
	Trap maintained at ~30˚C	(3 min)	N/A with He, 16 ml•min -1	flushed	reactor	opened,	valve	inlet line	to 200°C,	inlet & N/A outlet lines	N/A Reactor,	See previous column	N/A N/A	N/A Collected at 50 °C, desorbed at 300 °C for 2 min	Trapping Conditions Trapping Conditions
	SAM-like online setup (sample reactor oven)		Benchtop Online in reactor bed (Meunier et al. 2007) homemade reactor Benchtop Online in quartz boats for Online CDS5100 pyroprobe using Benchtop Benchtop Online in small reactor Benchtop	Derivatization Oven Derivatization Oven
	MTBSTFA 150 µL MTBSTFA/ only (direct derivatization) DMF (4:1)	DMF (5:1) or	MTBSTFA/	500 µL of	MTBSTFA/ DMF (3:1 or 4:1 depending on test) (one-pot, spiked) 100 µL MTBSTFA 40µL MTBSTFA/ DMF (3:1) (online with soil) 15µL MTBSTFA/ DMF DMF (7:3) 15 µL MTBSTFA/ 12 µL 30 µL MTBSTFA MTBSTFA/ DMF (5:1) (solvent extraction); (4:1) (campaign), 5 µL (4:1) (lab) DMF (4:1)	MTBSTFA/	l i DMF (3:1) (solvent 50 µL MTBSTFA/ i 40 µL MTBSTFA/ extraction); 100 µL DMF (4:1)	Derivatization reagent/solvent Derivatization reagent/solvent
	300˚C for 3 min; sealed in ~7 mbar CO2 environment	75˚C, 15 min 70˚C, 30 min (solvent extraction) Not specified for 75˚C, 30 min online with soil 80˚C for 30 min; 300˚C (flash) 70˚C, 30 min 300˚C for 3 min 175˚C, 10 min (campaign sample test); 75˚C, 10 min (lab & campaign blank) 75˚C, 15 min	Derivatization protocol Derivatization protocol
	120°C Depends on experiment (10') to 50 °C (2) to 220°C, 10˚C•min -1 ; to 320˚C, 20˚C•min -1 70˚C (5') to 300˚C (5'), 250˚C, 10˚C•min -1 3˚C•min -1 ; (campaign) hold for 1 50˚C to min; to 40 °C, 5 min, 300˚C, 10˚C•min -1 90˚C-250˚C, 3˚C•min -1 10˚C•min -1 , 60 °C, 3 min, 3˚C•min -1 , 120 °C, 5˚C•min -1 , 80°C to 125°C, 4˚C•min -1 ; to 100-270˚C, 3˚C•min -1 300°C, 30˚C•min -1 140˚C (10) to 300˚C, 10˚C•min -1 300˚C (3'), (lab) 90˚C (5 min) to 270˚C, 6˚C•min -1 to 300˚C (3 min) , 10˚C•min -1 6˚C•min -1	GC Col. T GC Col. T
																				300	°C
	1.6 mL•min -1	19.5 kPa 1.5 mL•min -1 0.9 mL•min -1 1.3 mL•min -1	1.1 mL•min -1 690 mbar (campaign), 903 2.07 bar mbar (lab)	1.3 mL•min -1 1.5 mL•min -1	Flow rate Pressure Flow rate Pressure
	Splitless			Splitless			1:100			1:20 Splitless 1:25 (calibration 1:100 experiments) 20 mL/min	1:20 or 1:50 Depends on experiment Not specified	SR or Split Flow SR or Split Flow
		N/A						1 Not specified (offline) 0.5	Not given	0.5 2 (campaign), 0.1 (lab) Depends on experiment	0.5	0.5 N/A	Injection (µL) Injection (µL)
	Without ultrasonic Carbonate-01, ND in extraction, AA ND (spiked samples). Pro, Leu in other samples	pot.	Yes; only trace levels when sample spiked with " optimistic" Mars sample-like concentrations spiked); Ala, Gly, Val (one-pot, non-spiked) AA from garden All AA detected 5 AA (Gly, Ala, Val, Leu, Iso) Gly, Ala, Val, Norleu (H2O only; H2O:isopr. extraction); Ala, Gly (isopr. extraction); AA detected in one-soil, ND from Atacama sample Atacama from pseudomonas sample mixed with silica, ND ND (campaign), Ala, Gly, Val, Leu, Isoleu, Pro (lab, Botnia only) Pro, Oxo-Pro, Phe	recovery (one-pot,	Yes, all within nominal MOMA run time ND (thermodesorption, spiked); all detected (non-spiked,solvent extraction); all detected, varied Ala (sample E3), Pro (sample E2)	Detection of AA Detection of AA
	0.01-0.02 nmol/g				5-6 nmol/g (Ala, Gly, Glu); 0.7 nmol/g (Ser) 7-18 pmol (standards, 0.5-1 nmol (standards) N/A N/A	N/A N/A	N/A	N/A N/A	LOD LOD

Table 26 :

 26 Evaluation of MOMA-like experimental setups for laboratory-based derivatization of natural samples. 1 = most suitable, 2 = comparable suitability, 3 = least suitable.

	Offline direct	Online reactor
	derivatization	derivatization

Table 27 :

 27 Summary of the oddities related to double, multiple, missing, unexpected, ghost or wide peaks on a homemade laboratory setup. *This item refers to the production of compounds including benzene and toluene which are known degradation products of Tenax TA under heating

Table 28 :

 28 Proposed potential types of odd peak behavior in systems with complex gas pathways and adsorption/thermal desorption trapping and a summary of general explanations for these behaviors and possible correlations to system conditions. earlier than expected in the run, in addition to peak at the expected retention time. The peak has a smaller peak area than peak at expected retention time. The two peaks are fully separated. 1.1. Double injection due to the time differential in valve switching and the start of the IT heating (Figure 88). 1.2. Injection parameters (long injection or low trapping) temperature. 2 A peak appears later than expected in the run, in addition to peak at expected retention time. The peak has a smaller peak area than peak at expected retention time. The two peaks are fully separated 2.1. Double injection due to the time differential in valve switching and the start of the IT heating (Figure 88). 2.2. Injection parameters (long injection or low trapping) temperature. 3

	#	Summary of types of odd peak behavior	General explanations
			Correlations
	1	A peak appears

Acknowledgements

This chapter is based on an article published in the Journal of Geophysical Research: Planets. Thank you to the co-authors of that article, Richard Quinn, Rafael Navarro-González, Alfonso Davila, and Chris McKay, in addition to my thesis advisors. This work could not have been conducted without the continuous support of Dave Williams, Allison Lopez, Danny Hoag, Sharlene Rhodes, and Barbara Pope from the NASA Space Science Data Coordinated Archive (NSSDCA) group at the NASA Goddard Spaceflight Center. The original Viking GC-MS data can be accessed at the NSSDCA in Greenbelt, Maryland.

I honor and thank the late Klaus Biemann for his irreplaceable contribution to the search for organics on Mars and for his invaluable advice and encouragement in the early stages of this work.

Acknowledgements

Thank you to Isis Criouet and Morgane Bance for their assistance in the lab. This work was supported by a grant from the French national space agency, the Centre National d'Etudes Spatiales (CNES).

Thank you to Desmond Kaplan, Ryan Danell, Andrej Grubisic, Xiang Li, and Sam Larson for organization and implementation of the 2018 GC-MS coupling campaign at the GSFC in conjunction with the French MOMA GC team.

Thank you to Noel Grand for providing the information on the adjustability of MOMA's flow rate and column temperature settings.

Thank you to Fabien Stalport for reviewing a report on MOMA FM and ETU data analysis, part of which appears in this chapter, and for providing suggestions.

Acknowledgements

Thank you first and foremost to Teresa Fornaro, without whom the opportunity to work on this study during the thesis would not exist. Thank you for preparation and distribution of the samples, substantial characterization work on the samples, organization of the sample testing campaign across the MOMA ALD, and consistent feedback on this work throughout the experimentation and analysis efforts.

The GC-MS experimental test plan was established and implemented in conjunction with the MOMA GC team, including Caroline Freissinet who conducted some of the pyrolysis tests and Arnaud Buch who conducted the TMAH thermochemolysis tests. Data treatment, analysis, and interpretations presented in this thesis are the work of Melissa Guzman with input from advisors and reviewers.

Thank you to Hugh Hill for discussions regarding the pedagogy of this chapter.

Thank you to MOMA team member Manuel Reinhardt for helpful discussion and literature suggestions regarding the pyrolysis results.

Thank you to the MOMA team, especially Xiang Li and the MOMA LD-MS team and the ALD combined science group, for discussions about this work.

Acknowledgements

Thank you to Daniel Glavin for providing the ASAP Atacama samples.

the derivatization reagent (either MTBSTFA/DMF (3:1) or DMF-DMA) was applied directly to about 5 mg of sample and sealed in a glass ampule. The sample was heated at 140 C (DMF-DMA), 200 C (DMF-DMA) or 250 C (DMF-DMA, MTBSTFA) for 3 min to allow the derivatization reaction to occur. The temperature for DMF-DMA was varied after the organic compounds were not clearly detected using the nominal derivatization temperature (140˚C) for MOMA. These derivatization protocols are modified from those determined to be optimal for chemical standards [START_REF] Freissinet | Search for evidence of life in space: Analysis of enantiomeric organic molecules by N,N-dimethylformamide dimethylacetal derivative dependant Gas Chromatography-Mass Spectrometry[END_REF][START_REF] Mackenzie | Analysis of amino acids by gas-liquid chromatography as tert.-butyldimethylsilyl derivatives. Preparation of derivatives in a single reaction[END_REF]) in order to aid thermal desorption of organic matter from the mineral [START_REF] Goesmann | The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments[END_REF]). The direct derivatization was intended to more closely mimic the MOMA derivatization procedure. The solvent extraction and direct derivatization procedures are illustrated in a cartoon in Figure 48. In both the solvent extraction and direct space experiment. The chapter emphasizes the increasing complexity to interpretation of both flight-like data and data collected for natural samples through preliminary tests on laboratory setups for MOMA-like thermodesorption and derivatization of natural samples. The chapter is concerned with the following fundamental questions of this thesis (Chapter I, Section I.4): §.4 What are the capabilities and limitations of space instrument components to detect organic molecules on Mars? §.5 Are there analytical biases and/or constraints related to the flight-like GC-MS analysis, laboratory setups, and/or their fidelity to the flight experiments of interest and sample analogs? If so, what are some solutions or ways to better simulate the experiment in the laboratory?

VI.2. Conclusions, results, recommendations and future work

The main conclusions and recommendations proposed by this thesis can be found at the end of each chapter (Sections II.5,III.4,IV.4,and V.5). A summary of general conclusions of this thesis as they connect to thematic science questions are summarized in Table 29, along with recommended future work related to the themes of this thesis (Perspectives).

Table 29: A summary of the general conclusions of this thesis as they connect to thematic science questions, along with perspectives on future work related to the themes of this thesis.

Science Questions

General Conclusions Perspectives 1. Are there organic compounds present in this sample?

• Viking detected additional organic compounds. • New MOMA retention time library will enable organic identifications in martian data. • Recovery of organics is enabled by space experiment one-pot/one-step (doped samples).

• Are there other unidentified organics present in the Viking data? • What is the synergy of the MOMA GCMS and LDMS/ALD to conduct an organic inventory on Mars? 2. If yes to (1), what is the origin of the organic compounds?

• Origin of chlorobenzene in VL-2 is not constrained. • Doped sample analysis provides database of pyrolysates and derivatives of target compounds.

• What is the carbon source of the chlorobenzene? • What is the organic instrument background for ExoMars?

3. What are the preservative or destructive effects of the sample on organic compounds?

• Oxychlorine species may inhibit recovery of pristine organics (Viking). • Perchlorate does not impede detection of organics (doped samples).

• What is the recovery of organics across different minerals? • What is the effect of perchlorate in the presence of realistic organic abundances?