S De Angelis
email: simone.deangelis@inaf.it

F Tosi

C Carli

S Potin

P Beck

O Brissaud

G Piccioni

M C De Sanctis

F Capaccioni

Temperature-dependent, VIS-NIR reflectance spectroscopy of sodium sulfates

Hydrated sodium sulfates have been suggested to be present in variable amounts in Solar System objects such as Mars and Europa, among the possible others. The presence of these hydrated species is related to current/past aqueous environments, thus has an importance regarding the potential habitability of planetary objects. In this study, we analyzed anhydrous sodium sulfate (thénardite) and the hydrated sodium sulfate (mirabilite) by means of visible-infrared reflectance spectroscopy in the 0.4-5 µm spectral range, at different low temperatures between 80 and 298K. Each mineral has been analyzed in three different grain sizes, between 36-150 µm. The anhydrous compound, thénardite, is characterized by a nearly flat spectrum in the visible and near IR up to 2.6 µm, while in the 3-4 µm region, the spectrum shows a few weak features due to H 2 O and SO 4 2-overtones/combinations. The first strong SO 4 2-overtone is visible at 4.6 µm. Spectra of mirabilite are substantially characterized by H 2 O absorption features in the 1-3 µm region, and by sulfate overtone/combination bands occurring at 3.8 and 4.7 µm. A weak feature appearing at 2.18 µm is also putatively attributed to the sulfate ion. The bands show changes as a function of temperature. The hydration absorption features in mirabilite show the strongest dependence with temperature, both in terms of shift in position and change of spectral shape. Bands at 3.1-3.24 µm in thénardite, as well as absorption features located at 1.78 and 2.47 µm in mirabilite, could be used as diagnostic proxies for the detection of these two minerals on planetary bodies.

Introduction

Sodium sulfates compounds occur widely on Earth in different hydration forms and in various geological settings. On other Solar System bodies they have been proposed to be present on the surface of Europa (mirabilite) and on Mars (mirabilite and thénardite).

Earth

Sulfate minerals form on Earth in several geological environments, mainly (i) as evaporitic deposits, (ii) after oxidation of sulfides in hydrothermal systems, (iii) as products of weathering of volcanic rocks [START_REF] Christy | Sulfate Minerals[END_REF]. In particular evaporitic sulfate minerals are important indicators of geological evolution and past climatic conditions. They maintain a record of the source water geochemical features and of the evolution of environmental parameters driving the evaporation processes.

De Angelis et al. 2021, Icarus, 357, 114165 The process of evaporation typically occurs from concentrated water solutions or brines, in which are present readily soluble salts. The precipitation starts after the brine becomes saturated in a given salt, and the water loss must exceed the water gain. Brines can be characterized by a wide range of ionic strength, can have multiple dissolved salts, with different solubility. The crucial parameters governing the evaporative process are temperature, humidity, air movement, salinity and pH (Babel and Schreiber, 2014). The evaporation rate is favored by high temperature, low relative humidity and air movement, while it is inhibited for example by the increase in salinity of the evaporating brine itself. On the opposite also the freezing process, by removing liquid water from the brine with consequent ice formation, can result in the precipitation of certain cryogenic sulfate salts (Babel and Schreiber, 2014;[START_REF] Herrero | Thénardite after mirabilite deposits as a cool climate indicator in the geological record: lower Miocene of central Spain[END_REF]. With this regard, brines having eutectic temperature below 0°C are defined cryobrines.

Specifically thénardite and mirabilite occur on Earth both in open and closed basins, that are in marine and lacustrine evaporitic deposits [START_REF] Jones | Geochemistry of Saline Lakes[END_REF]Babel and Schreiber, 2014). The mineralogy of precipitated compounds depends on the composition of the salts dissolved in the brine, and on the proportions between ions, as well as on the driving process (evaporative or cooling/freezing). Brines that can result in the precipitation of thénardite and mirabilite are of three types: (i) Na-CO 3 -SO 4 -Cl-(K), (ii) Na-SO 4 -Cl-(K) and (iii) Mg-Na-SO 4 -Cl-(K) [START_REF] Eugster | Geochemistry of Evaporitic Lacustrine Deposits[END_REF][START_REF] Warren | Evaporites: Sediments, Resources and Hydrocarbons[END_REF]. Na-sulfate salts (anhydrous and hydrated) are generally found in the same environment. Thénardite and mirabilite can crystallize from brines in which HCO 3 -exceeds Ca 2+ : that is in carbonate-rich, calciumpoor, sulfate-enriched waters, so that Ca-sulfates cannot form [START_REF] Hardie | The evolution of closed-basin brines[END_REF][START_REF] Jones | Geochemistry of Saline Lakes[END_REF].

Sodium sulfates are strongly temperature dependent: on Earth, the anhydrous form thénardite typically is formed in hot and arid climatic conditions, while mirabilite is a typical product of cool periods [START_REF] Herrero | Thénardite after mirabilite deposits as a cool climate indicator in the geological record: lower Miocene of central Spain[END_REF]. Thus thénardite is found on Earth both in recent and in ancient deposits, as primary precipitation product of warm brines in shallow lakes or as efflorescent crust in playa environments [START_REF] Herrero | Thénardite after mirabilite deposits as a cool climate indicator in the geological record: lower Miocene of central Spain[END_REF]. Mirabilite instead is not found in ancient environments: this is due to its high reactivity and sensitivity to temperature changes, as it readily can dehydrate and transform to thénardite. The process of transformation of mirabilite to thénardite is temperature dependent: the dehydration occurs at 32°C, in presence of NaCl it occurs at 18°C, while it drops down to 16°C in presence of Mg 2+ ions [START_REF] Herrero | Thénardite after mirabilite deposits as a cool climate indicator in the geological record: lower Miocene of central Spain[END_REF]. Transformation of mirabilite to thénardite also depends on relative humidity [START_REF] Steiger | Crystallization of sodium sulfate phases in porous materials: The phase diagram Na 2 SO 4 -H 2 O and the generation of stress[END_REF]. Secondary thénardite can be formed as a consequence of diagenesis of other minerals, typically mirabilite dehydration. Both thénardite and mirabilite however can precipitate during evaporative (high temperature) and cooling/freezing (cryogenic) processes. Precipitation of mirabilite from a cooling brine starts at lower temperatures as its concentration decreases. On Earth, mirabilite mounds have been also found in Antarctica, and interpreted as evaporative/freezing precipitation products in subglacial environments [START_REF] Socki | Antarctic Mirabilite Mounds As Mars Analogs: The Lewis Cliffs Ice Tongue Revisited[END_REF].

Mars

The identification of sulfates, both anhydrous and hydrated, on Martian surface, is important in order (i) to infer clues about the amount of water bound in regolith and rocks, and (ii) to better understand the past climatic evolution. Sulfates on Mars are interpreted to be formed as (i) primary evaporite minerals or as (ii) secondary weathering products.

Sodium sulfates have been inferred to be present on Mars on the basis of geochemical modeling and chemical composition measurements. Anhydrous and monohydratedpolyhydrated sulfates, hosting various types of cations (mostly Ca/Fe/Mg), have been detected at different locations on Mars by remote-sensing VIS-NIR spectroscopy with Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) onboard Mars Express and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter instruments, and reported by a vast literature [START_REF] Gendrin | Sulfates in Martian Layered Terrains: The OMEGA/Mars Express View[END_REF][START_REF] Murchie | A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter[END_REF][START_REF] Mangold | Spectral and geological study of the sulfate-rich region of West Candor Chasma[END_REF][START_REF] Flahaut | Sulfate-Rich Deposits On Mars: A Review Of Their Occurrences And Geochemical Implications[END_REF]. On the basis of OMEGA spectral data, hydrated Na-sulfates could be present in the West Chandor Chasma within Valles Marineris [START_REF] Mangold | Spectral and geological study of the sulfate-rich region of West Candor Chasma[END_REF]. Sulfur-bearing compounds are thought to be present at the Mars Pathfinder landing site based on alpha proton X-ray spectrometer (APXS) data [START_REF] Foley | Final chemical results from the Mars Pathfinder alpha proton X-ray spectrometer[END_REF]. In particular, thénardite and mirabilite have been suggested to be present at the Mars Pathfinder landing site: according to the strong correlation found between Na 2 O and SO 3 , Na 2 SO 4 is likely to be present in rock samples and in rock-weathering crusts, while it is less likely to be present in soil [START_REF] Zolotov | Mineralogy, Abundance, And Hydration State Of Sulfates And Chlorides At The Mars Pathfinder Landing Site, 35th Lunar and Planetary Science Conference[END_REF]. Sulfur-bearing compounds have also been inferred to be present at Meridiani Planum by APXS instrument onboard MER Opportunity rover [START_REF] Brueckner | Sulfur concentrations of the Martian surface derived from orbital Mars Odyssey GRS and in-situ MER APXS measurements: implications on the selection of future landing sites[END_REF]. Analyzing the 6.1-µm bound-water band in Thermal Emission Spectrometer (TES/Mars Global Surveyor) spectra, [START_REF] Kuzmin | Global Mapping Of Martian Bound Water At 6.1 Microns Based On Tes Data: Seasonal Hydration-Dehydration[END_REF] suggested the presence of Na-sulfates in belts surrounding the ice in the polar caps, subject to seasonal cycles of hydration/dehydration. Moreover, sodium sulfates are predicted to be present according to modeling of chemical divides applicable to Martian evaporating brines, characterized by acidic conditions more than on Earth [START_REF] Tosca | Chemical divides and evaporite assemblages on Mars[END_REF].

Europa

The data from Galileo Near-Infrared Mapping Spectrometer (NIMS) led to the prevailing view that Europa's endogenous units are rich in sulfate salts (McCord et al., 1998a, 1998b, 1999, 2010[START_REF] Dalton | Linear mixture modeling of Europa's non-ice material based on cryogenic laboratory spectroscopy[END_REF]. The deca-hydrated form of sodium sulfate (mirabilite) has been initially proposed as one of the candidate materials for the heavily hydrated salts, thought to constitute the "non-icy" regions of the trailing hemisphere of Europa, on the basis of Galileo/NIMS VIS-IR spectral data (McCord et al., 1998a(McCord et al., , 1998b[START_REF] Mccord | Hydrated salt minerals on Europa's Surface from the Galileo near-infrared mapping spectrometer (NIMS) investigation[END_REF][START_REF] Mccord | Hydrated minerals on Europa's surface: An improved look from the Galileo NIMS investigation[END_REF]. The occurrence of heavily hydrated salts on the surface of Europa was initially suggested because of the distorted spectral shape of hydration bands at 1.5 and 2 µm in NIMS data, notably different from more symmetric pure water ice absorption bands; nevertheless the same spectral data were also interpreted with the presence of hydrated sulfuric acid of Iogenic origin [START_REF] Carlson | Europa's Surface Composition[END_REF] and more recently with Mg-bearing chlorinated salts [START_REF] Ligier | VLT/SINFONI Observations of Europa: New Insights into the Surface Composition[END_REF]. [START_REF] Vu | CHEMISTRY OF FROZEN SODIUM-MAGNESIUM-SULFATE-CHLORIDE BRINES: IMPLICATIONS FOR SURFACE EXPRESSION OF EUROPA'S OCEAN COMPOSITION[END_REF] suggest, on the basis of experimental measurements of frozen brines, that mirabilite and MgCl 2 are expected to precipitate on the surface upon ocean freezing. The presence of hydrated salts on the surface of Europa, of endogenic origin, could be evidence of rising of materials from the ocean below the icy crust, with consequent deposition on surface after brines sublimation. This has consequences for understanding the dynamics and chemical mixing within the liquid ocean and then astrobiological implications.

Previous laboratory studies

Several authors have studied sulfates in laboratory, by means of VIS-IR reflectance spectroscopy, although very few investigated sodium sulfates. The first study to report infrared reflectance spectra of sulfates was the work by [START_REF] Omori | Infrared studies of saline sulfate minerals[END_REF]. In their study they reported infrared spectra of a great number of anhydrous and hydrous sulfates, including thénardite: spectra were acquired in the 2-15 µm range at room P-T conditions. [START_REF] Crowley | Visible and Near-Infrared (0.4-2.5 µm) Reflectance Spectra of Playa Evaporite Minerals[END_REF] measured VIS-NIR spectra (0.4-2.5 µm) of tens of playa evaporite minerals, in particular also thénardite and mirabilite. Spectra were acquired on coarse powders (250 µm) and at room P-T conditions, after drying at 60°C for few minutes. Thénardite was also measured by [START_REF] Vassallo | Infrared Emission Spectroscopy of Some Sulfate Minerals[END_REF] in the mid-IR range in emissivity, at temperatures >50°C. [START_REF] Mccord | Thermal and radiation stability of the hydrated salt minerals epsomite, mirabilite, and natron under Europa environmental conditions[END_REF] investigated three heavily hydrated minerals, including mirabilite, in the IR range 1-2.7 µm, in vacuum and in the temperature range 100-375K. [START_REF] Dalton | Spectral comparison of heavily hydrated salts with disrupted terrains on Europa[END_REF] measured spectra of mirabilite in the 0.35-2.5 µm range in the 50-250K temperature interval. [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF] investigated by reflectance spectroscopy a large number of sulfates in a broad IR range, although they did not study Na-sulfates. [START_REF] Bishop | Combined VNIR and Raman spectroscopy of the Atacama salt flats as a potential Mars analog[END_REF] and [START_REF] Flahaut | Remote sensing and in situ mineralogic survey of the Chilean salars: An analog to Mars evaporite deposits?[END_REF] studied evaporite assemblages in Chilean salars, by means of field VIS-NIR spectroscopy, including mirabilite. Thus most of studies have focused on the VIS-NIR spectra of sodium sulfates, or typically at ambient temperature. Spectra in the >2.5-µm region at cryogenic temperatures are lacking, as well as spectra of samples with different grain sizes.

Methods

Experimental setup

The spectral measurements were performed at the Institute de Planétologie et d'Astrophysique de Grenoble (IPAG), with the SHINE Spectro-Gonio Radiometer facility [START_REF] Brissaud | Spectrogonio radiometer for the study of the bidirectional reflectance and polarization functions of planetary surfaces: I. Design and tests[END_REF]. Reflectance spectra were acquired in the Visible-Near Infrared (VIS-NIR) range 0.4-5.0 µm, using a monochromator light source. The spectral range is covered thanks to a Si-diode (λ<1 µm) and an InSb detector (λ>1 µm). Optical fibers mounted on the goniometer arms permit homogeneous illumination of the sample and collection of the reflected light within a narrow solid angle. Data were acquired with a constant spectral sampling of 20 nm and a spectral resolution varying between 5 and 38 nm (value increasing, i.e. worsening, by about a factor 2 at each grating change with increasing wavelength) across the whole range. The samples to be measured were put in an aluminum sample holder cup, with diameter 48 mm and >5 mm deep; the cup is mounted within the CarboN-IR environmental cell, purged with gas N 2 flux at 1 bar atmosphere. This internal cell is placed inside an external cell, in which high vacuum is performed [START_REF] Grisolle | Les condensats saisonniers de Mars : étude expérimentale de la formation et du métamorphisme de glaces de CO2[END_REF]; https://coldspectro.sshade.eu/carbo-nir-simulation-chamber).

Measurements were carried out at 12 different temperatures in the overall 80-298K range, at steps varying from 10 to 25K, using a 4 He Stirling cycle-cryostat and a Lakeshore temperature controller with +/-0.1K error. Once a given temperature was reached, the data acquisition started after 5 minutes to allow for thermal stabilization of the sample. The instrument usage, temperature control and data acquisition and calibration were managed through LabVIEW procedures developed at IPAG [START_REF] Potin | SHADOWS: a spectro-gonio radiometer for bidirectional reflectance studies of dark meteorites and terrestrial analogs: design, calibrations, and performances on challenging surfaces[END_REF].

Samples

Two mineral samples were analyzed, namely anhydrous sodium sulfate, Na 2 SO 4 (thénardite) and sodium sulfate decahydrate, Na 2 SO 4 10H 2 O (mirabilite). The compounds were purchased on the market from Sigma Aldrich, and certified with >99% purity. Each mineral was measured in three different grain size ranges: 36-50 µm, 75-100 µm and 125-150 µm. The grain size ranges were chosen in order to be representative of planetary regoliths in the fine, medium and coarse regime, and in such a way to avoid overlapping among them. The mineral powders were produced starting from coarse fragments, by grinding with agate mortar and sieving. This preparation was done at Sample Preparation Facility at IAPS-INAF. The nominally anhydrous sample (thénardite) was stored at IPAG for several days before measurements in a desiccator cabinet under controlled humidity, with the goal of minimizing the amount of adsorbed room water vapour.

Acquisitions and data treatment

Measurements were carried out at 12 different temperatures in the overall 80-298K range, at increasing steps of 10 to 25K, on all samples and grain sizes. For each sample, the measurement cycle was: (i) first acquisition at room temperature (varying between 275-304K), called "T-down", (ii) cooling down the sample to 80K, (iii) acquisitions at the selected temperatures during the warming up of the sample, up to room temperature (the latter called "T-up"). In some case the spectra at 140K were taken both during the cooling and warming phases, to check for any potential, macroscopic physico-chemical changes in the sample.

LabSphere © Spectralon and Infragold were acquired in air outside the cell as reference targets, to cover the spectral range <2 µm and >2 µm respectively. In the calibration procedure, a photometric correction that takes into account the contribution of the optical window is applied. Data analyses were carried out by using a LabVIEW tool for spectral fitting developed at IAPS. Spectral parameters were retrieved for each analyzed absorption band, for all samples. The analyzed parameters were: (i) band position, (ii) depth, (iii) area and (iv) width. The position was computed after continuum removal: the continuum was calculated as a straight line between the wavelength edges (λ i -λ f ) of each main band; after dividing the spectrum by the continuum line, the band position (B C ) was calculated by using three different approaches: (a) taking the minimum value of reflectance; (b) by locally fitting data around the minimum with a spline curve, whose minimum yields the band center; (c) fitting around the minimum with a second degree polynomial. We used the method (c) for well defined bands containing a sufficiently high number of sampling points. For weak bands poorly sampled, we used the approaches (a) and (b). The band depth (B D ) was computed according to the formula [START_REF] Clark | Reflectance Spectroscopy: Quantitative Analysis Techniques for Remote Sensing Applications[END_REF]:

𝐵 ! = 1 - 𝑅 ! 𝑅 !
in which R B is the reflectance at the band center and R C is the interpolated value of the spectral continuum at the same wavelength. The band area (B A ) parameter is computed, after continuum removal, with the following formula:

𝐵 ! = 𝐴 ! -𝐼 !
where A R is the rectangular area comprised between λ i -λ f and R=1, and I B is the integral defined between λ I and λ f , which delimits the band. Finally, the band width (B W ) is computed as the Full Width at Half Maximum corresponding to the band center. In order to evaluate the variability of such parameters and to provide an estimate of the errors, the procedure for the retrieval of parameters has been repeated four times, each time making the λ i -λ f to vary by ±20 nm, i.e. slightly changing the position of the anchor points of the continuum line

Results

Spectral measurements

In this section we describe the spectral data acquired on the two sulfate salts in a broad range of temperatures (Fig. 1 and2). For each sulfate, we separately show the spectra of the three grain sizes (De Angelis et al., 2018a[START_REF] Angelis | VNIR reflectance spectra of Mirabilite (Na 2 SO 4 10H 2 O) with 3 different grain sizes and at variable temperature (80-298K). SSHADE/REFL_SLAB+CSS[END_REF] (fig. 3).

Anhydrous sodium sulfate

The spectra of thénardite acquired at different temperatures are shown in Fig. 1 for the three considered grain sizes. The spectra are flat, featureless and slightly red-sloped up to <2.5 µm. A very weak absorption band near 2 µm and a broad one at 3 µm testify the presence of some water adsorbed in the grains, although the nominally anhydrous sample was stored in a desiccator cabinet with low humidity days before the measurements, and only a few minutes passed between the extraction of the powder and its positioning in the cell for analyses. This happens because this sample is very hygroscopic. However, it should be considered that this water band is due to fundamental vibration modes of the molecule and has thus a very high absorption coefficient making it to appears even with very low amounts of adsorbed water, <<1 wt% [START_REF] Salisbury | Thermal Infrared (2.5-13.5 µm) Spectroscopic Remote Sensing of Igneous Rock Types on Particulate Planetary Surfaces[END_REF][START_REF] Pommerol | Water sorption on Martian regolith analogs: thermodynamics and near-infrared reflectance spectroscopy[END_REF]. Absorption features due to adsorbed water are reported at wavelengths 1.41 and 1.92 µm [START_REF] Crowley | Visible and Near-Infrared (0.4-2.5 µm) Reflectance Spectra of Playa Evaporite Minerals[END_REF]. The feature appearing at 2.6 µm is due to the presence of a fluctuating amount of water vapour in the room that is not perfectly compensated with the calibration reference. A number of absorption bands occur in the 3-4 µm range. These bands are centered at 3.1, 3.2, 3.42-3.50, 3.68 and 3.86 µm. The features appearing at 3.1 and 3.2 µm are likely due to the presence of water in the sample [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF], although these two bands are observed also in other sulfates [START_REF] Bishop | Spectral properties of Ca-sulfates: Gypsum, bassanite and anhydrite[END_REF]. The two minima at 3.42-3.5 µm seem to belong to a single, broader band. These features are not strictly vibrations of the sulfate; rather they could be related to vibration modes of water molecules linked to the sulfate. Alternatively this feature could be due to C-H vibration, putatively from organic contamination. Indeed also a very small amount (<1%) of organic contamination occurred during the sample preparation or measurement could be responsible of such band. Few literature data exist relative to the bands at 3.68 and 3.86 µm. A band at 3.87 µm, attributed to overtone or combination of SO 4 2-fundamental modes, is reported for the mineral coquimbite while for other sulfates this band is reported to be near 4.0 µm [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]. The fundamental vibrations of SO 4 2-are located near 9 µm (symmetric and asymmetric stretching at 981 and 1104 cm -1 [START_REF] Bishop | The visible and infrared spectral properties of jarosite and alunite[END_REF]). In the 4-5 µm region several overtone/combination modes of S-O occur [START_REF] Bishop | The visible and infrared spectral properties of jarosite and alunite[END_REF][START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]. The first overtone of such fundamental band occurs near 4.6 µm. This appears as a broad and intense doublet of bands, with minima near 4.45 and 4.6 µm, separated by an interband peak (minimum of absorption) at 4.53 µm. The minima in these bands become less sharp and more flattened with increasing grain size. In the coarser grain size the band is almost saturated and minima are no longer discernible (fig. 1).

Sodium sulfate decahydrate

The spectra of sodium sulfate decahydrate (mirabilite) are shown in Fig. 2. Spectra are flat and featureless in the visible range up to 1 µm. The slope in this range tends to become bluer (negative) with increasing grain size and decreasing temperature. Several absorption bands occur in the IR range 1-5 µm, most of them being due to structural H 2 O molecules in the hydrated mineral. Hydration absorption features occur at ambient temperature near 1.2, 1.46, 1.78, 1.96, 2.47, and 3.0 µm. A weak H 2 O band appears at 1 µm in the medium (75-100 µm) and coarse grain size (125-150 µm) spectra. On the high wavelength side of the 1.46-µm band, several minima appear as inflections at the lowest temperatures. In the 2-µm complex a secondary feature shows up near 2.2 µm. All these features are related to overtones and combinations of fundamental vibrational modes of the high number of water molecules within the mineral [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]. These absorption features are also consistent with measurements by [START_REF] Crowley | Visible and Near-Infrared (0.4-2.5 µm) Reflectance Spectra of Playa Evaporite Minerals[END_REF]: in the 2.2-µm region he reports two features centered at 2.18 and 2.24 µm. The 2.47-µm feature can be due to a combination/overtone of stretching and bending modes of H 2 O or to the 3ν 3 overtone of the fundamental asymmetric bending mode of SO 4 2-(ν 3 , 7.8-10.4 µm) [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]; nevertheless, the circumstance that this band only appears in the hydrated sample and not in the anhydrous one, could be an indication of a water origin. Two other bands appear at 3.8 µm and 4.6 µm, both related to overtone/combinations of S-O fundamental modes. The first is weak and only visible at the lowest temperatures (T < 140K), while the second is very broad and intense, with its long-wavelength edge occurring beyond 5 µm. The features appearing in the 4-5 µm region are interpreted as first-order overtones and combinations of the fundamental asymmetric bending mode ν 3 of SO 4

2- [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]. The 1.20 and 1.46-µm bands are not/partially visible in 80 and 205K spectra of the 36-50 grain size, respectively, due to instrumental artifacts occurred during this acquisition in the 1.1-1.4-µm spectral range.

Spectral analysis

In this section we report the results of the spectral analysis carried out for the two sulfate compounds described in this paper, according to the procedures for parameters retrieval described in Section 2. The four parameters have been calculated at all measured temperatures with the aim to highlight their temperature dependence. In Table 1, we list all the identified spectral features for the two sulfates, with information about their assignment, when known, and about the analyses. In the following we only present and discuss parameters that display significant trends as a function of temperature. The continuum-removed bands are shown in Fig. 4-5 for thénardite and in Fig. 7 for mirabilite.

Regarding the thénardite, none of the absorption features displayed by the nominally anhydrous compound show any significant wavelength-dependence on temperature, at least at the spectral resolution of the measurements, except the 3-µm water band, which is due to water adsorption as explained in the previous section. [START_REF] Clark | High spectral resolution reflectance spectroscopy of minerals[END_REF] (2) [START_REF] Bishop | Spectral properties of Ca-sulfates: Gypsum, bassanite and anhydrite[END_REF] (2) [START_REF] Bishop | Reflectance spectroscopy and geochemical analyses of Lake Hoare sediments, Antarctica[END_REF] (2) [START_REF] Bishop | Spectroscopic analysis of martian meteorite Allan Hills 84001 powder and applications for spectral identification of minerals and other soil components on Mars[END_REF] (2) [START_REF] Bishop | Mineralogical and geochemical analyses of Antarctic sediments: A reflectance and Mössbauer spectroscopy study with applications for remote sensing on Mars[END_REF](6) [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF](7) [START_REF] Crowley | Visible and Near-Infrared (0.4-2.5 µm) Reflectance Spectra of Playa Evaporite Minerals[END_REF]

Anhydrous sodium sulfate 3-µm band

Spectral parameters retrieved for the 3-µm complex (Fig. 4) are shown in Fig. 6. For this feature, we computed the band area and the band width between the wavelengths 2.65-3.55 µm. Depth and area increase rather linearly as the temperature decreases, down to about 150K, then the values of these two parameters tend to sligthly decrease. The band position shows a nonlinear behavior as the temperature decreases: first it shifts from 2.95-2.96 µm (depending on grain size) towards shorter wavelengths, then it moves to longer wavelengths, it reaches a maximum at about 2.99 µm, then it goes back again to shorter wavelengths. For each grain size, the overall shift in the band center from the minimum value to the maximum value is about 40 nm. The maximum value is achieved at 150K.

The effect of grain size is different for the various parameters. The band position appears to be substantially shifted towards longer wavelengths for the "intermediate" grain size (75-100 µm) and towards shorter wavelengths for the "fine" grain size (36-50 µm); the "coarse" grain size (125-150 µm) being an intermediate case. Depth and area increase monotonically with grain size. The 3.1 µm and 3.24 µm bands due to H 2 O show a behavior similar to the previous feature (fig. 6); there is not any evident wavelength shift with temperature (<<5 nm), the depth increases up to a maximum value (for T=150K) and then it decreases very slightly as the temperature keeps on decreasing. Area and width behaviour with temperature are the same as for the 3 µm band.

3-4-µm region

The 3.4-µm feature, characterized by two minima at 3.42 and 3.5 µm, is consistent with the presence of very small amounts of C-H compounds (<1%) in the sample, given its similarity in terms of band position and shape to C-H features typically occurring in natural materials [START_REF] Bishop | Reflectance spectroscopy and geochemical analyses of Lake Hoare sediments, Antarctica[END_REF][START_REF] Bishop | Spectroscopic analysis of martian meteorite Allan Hills 84001 powder and applications for spectral identification of minerals and other soil components on Mars[END_REF][START_REF] Bishop | Mineralogical and geochemical analyses of Antarctic sediments: A reflectance and Mössbauer spectroscopy study with applications for remote sensing on Mars[END_REF]. Band parameters for the small features at 3.68 and 3.86 µm (Fig. 4) are shown in Fig. 1A (Online Supplementary Material). They are both characterized by a slight increase of band depth and area with decreasing temperatures; this effect is more marked at greater grain sizes. The position of features appear to be constant (within <2 nm) with temperature change. The effect of grain size is clear on depth and area: these parameters have larger values with increasing grain size.

4.6-µm band doublet

The continuum-removed band is displayed in Fig. 5 for the three grain sizes. Band parameters have not been retrieved for the sulfate 4.6-µm band doublet, because data beyond 4.8 µm are affected by a very low signal-to-noise ratio; for this reason, the band is incomplete and it was impossible to fix unambiguously the right edge wavelength for the continuum removal. Nevertheless, the effect of temperature is visible especially for the intermediate grain size: the band becomes narrower for decreasing temperature, with the interband 4.5-µm peak height increasing while temperature decreases. The effect of grain size is also rather clear: the bottom of the two components of the band becomes flatter, due to their saturation, and the slope decreases as the grain size gets larger (fine à medium à coarse).The absolute height of the interband peak at 4.53 µm also decreases.

Sodium sulfate decahydrate

The continuum removed absorption features of sodium sulfate decahydrate, or mirabilite, are displayed in Fig. 7. Some of them tend to exhibit a fine structure at the lowest temperatures. Band parameters as a function of temperature are shown in Fig. 8-9 (and fig. 2A in the Online Supplementary Material), for selected features of interest.

1.2-µm band

Band parameters are shown in Fig. 8 (left panels). This feature, which is related to H 2 O in the mineral structure proves to be strongly temperature-dependent in the considered range. The band position moves from about 1.21 µm at room temperature (300K) to 1.22 µm at the lowest temperature, with a total shift of about 11 nm. Depth and area increase quite linearly as the temperature drops down, by roughly 20%. The band width decreases monotonically with decreasing temperature, by more than 10%. The effect of grain size is very evident for all the four parameters. At a given temperature, the band center moves towards shorter wavelengths as the grain size becomes larger. Concerning the other parameters (depth, area and width), their value at a given temperature are greater for larger grain sizes.

1.46-µm band

Parameters are displayed in Fig. 8 (right panels). Also in this case the band center is notably temperature dependent, with a shift of about 6 nm towards longer wavelength with decreasing cryogenic temperature. Band depth and area increase monotonically with decreasing temperature, by a factor of about 10% and 14% respectively. The FWHM is characterized by a nonlinear behavior, increasing up to a maximum, at T=120÷180K depending on grain size, and then decreasing as the temperature decreases. This behavior could be a combined effect of the shift in position and the appearance of a shoulder around 1.55 µm on the high wavelength side of the band at the lowest temperatures (Fig. 7). Here the effect of grain size is clearer on depth, area and width parameters, for which the fine (36-50 µm) assumes values substantially lower than the other grain sizes.

1.78-µm band

The spectral parameters of this feature (Fig. 9, left panels) are characterized by a somehow different behavior with respect to the previous two bands. The band position moves to shorter wavelengths by 3-7 nm as the temperature decreases. Band depth, area and width all increase with decreasing temperature, by a factor of 36%, 40% and 14%, respectively. But below 100K, the trend reverse for the smallest grain size, only, with depth and area slightly decreasing . In general, band depth and area assume higher values for the larger grain sizes. The shift in position for a given temperature is not linear with grain size.

2.0-µm band

The behavior of this band with temperature is very similar to that of 1.46-µm feature (Fig. 8). The band center shifts by less than 10 nm towards longer wavelengths as the temperature decreases, in the range 1.96-1.97 µm. The shift in position is also grain size dependent, with the smaller grains (36-50 µm) positioned at shorter wavelengths, and the medium grains (75-100 µm) positioned at longer wavelengths. Depth and area slightly increase with decreasing temperature. Maximum values are assumed by the intermediate grain size, while minimum values by the fine grain size. Bandwidth increases monotonically with temperature decreasing, except for the fine grain size, for which it is maximum at 100K.

2.47-µm band

The spectral parameters for this feature are displayed in Fig. 9 (right panels). The band position does not appear to be significantly dependent on temperature: the measured shift is about 2-3 nm, which is well below the spectral sampling used for our measurements. Depth, area and width increase quite monotonically with temperature reduction, by a factor of 17%, 40% and 12% respectively. Depth and area assume maximum values for the intermediate grain size (75-100 µm) and minimum values for the fine grain size (36-50 µm). The bandwidth assumes increasing values linearly with increasing grain size. The behavior of depth, area and width as a function of temperature reduction is quite monotonic for the 75-100 µm-grain size; such parameters assume a narrow maximum peak at 100K for the 36-50 µm-grain size, then start to decrease; the maximum region is broad, a plateau extending for T<150K, for the (larger) 125-150 µm-grain size.

3.0-µm band

The continuum-removed band is shown in Fig. 7, and relative spectral parameters are displayed in Fig. 2A (Online Supplementary Material; left panels) against temperature. The position appears to be very sensitive to temperature change, and in a non-linear manner, although the band bottom is very broad and nearly flat. As the temperature decreases, the position shifts by more than 50 nm towards longer wavelengths; the shift becomes more than 100 nm for the 125-150-µm grain size (2.93-3.10 µm). At T=150K the position starts to shift back towards shorter wavelengths. This behavior could be ascribed to the beginning of separation of the two distinct water stretching modes, at 2.9 and 3.1 µm at this temperature. At a given temperature, the band position is shifted towards shorter wavelengths for the 36-50 µm-grain size, and towards longer wavelengths for the 75-100 µm-grain size. The depth has also a non-linear behavior, increasing up to a maximum at 150K and then decreasing, with temperature reduction. The band area shows a nearly monotonic decrease with temperature reduction, especially for the 36-50, but starting to display a sharp increase around 150K for larger grain sizes. Bandwidth shows a strong narrowing as the temperature decreases, by a factor of 20%.

3.8-µm band

The spectral parameters are shown in Fig. 2A (online supplementary material; right panels). This feature is weak and only shows up at temperature values below 180K; it proves to be significantly temperature-sensitive. The position shifts by about 15-30 nm towards shorter wavelengths as the temperature decreases (3.80-3.77 µm). Depth and area increase monotonically as the temperature decreases, by a factor of 5-10 depending on the grain size (fine or intermediate, respectively). The bandwidth increases with temperature drop off, reaching a maximum around 100K.

4.6-µm band

The strongest sulfate band in the explored spectral range, centered at about 4.6 µm, is displayed in Fig. 7. Because the upper limit of sensitivity of the SHINE facility is 5 µm, and the signal-to-noise is very low beyond 4.6 µm, it was impossible to properly measure the right shoulder of the band, making it hard to safely derive spectral parameters. Here we can qualitatively state that this feature appears substantially different in the decahydrate form with respect to the anhydrous form (compare Fig. 4 with Fig. 7). In mirabilite, this band is shifted towards longer wavelengths, with a unique minimum near 4.8 µm. The short wavelength edge is less steep than in the case of thénardite. In thénardite the band displays two minima at 4.45 and 4.60 µm, separated by an interband peak (minimum of absorption) at 4.53 µm. This peak does not appear in spectra of mirabilite.

Discussion

Effect of temperature on bands

In the thénardite spectra the 3-µm band complex is related to small quantities of ambient adsorbed water. This feature is very sensitive to temperature variation, although band parameters do not show a monotone trend. Minima at 2.9, 3.1 and 3.24 µm all increase in intensity (band depth) as the temperature drops down, reaching a maximum depth near 150-160K, then start to decrease as the temperature decreases to 80K. The increase in intensity is higher for the 3.1-µm feature than the other two features. At ambient temperature and at 80K the minimum (after continuum removal) of the band complex occur near 2.9 µm, while at the intermediate temperature 150K the minimum seems to be 3.1 µm (fig. 4). A similar behavior occurs for the 3-µm complex in mirabilite (fig. 2A), for which the 3.1-µm secondary minimum increases to its maximum intensity as the temperature drops down to 150K, then starts to decrease. This seems to indicate that a certain process is occurring in both samples, that causes the 3.1-µm feature to assume its maximum depth at about 150-160K. Taking into account that our spectra were taken during the heating phase (80à298K), an explanation could be given by water ice desorption, which occurs at 160K, as observed in [START_REF] Mccord | Thermal and radiation stability of the hydrated salt minerals epsomite, mirabilite, and natron under Europa environmental conditions[END_REF] after heating mirabilite from 100 to 375K during temperature-programmed-desorption experiments.

All other water-related bands in mirabilite (1.20, 1.46 and 1.96 µm) show the same behavior with temperatures, shifting towards longer wavelengths as the temperature decreases. This is consistent with studies on IR spectroscopy of water ice [START_REF] Grundy | The temperature-dependent near-infrared absorption spectrum of hexagonal H2O ice[END_REF]: the longward shift is due to an increase in hydrogen bond strength at lower temperatures. Bands at 1.78, 2.47 and 3.8 µm in mirabilite shift towards shorter wavelengths as the temperature decreases, that is in an opposite direction with respect to water-related bands, and they are likely due to vibrations in the sulfate ion.

vs 3.86 µm band

The 3.8-µm band in mirabilite, that could be attributed to sulfate, should correspond to a feature occurring in the anhydrous sample thénardite at 3.86 µm. The shift in position in mirabilite could be due to the presence of water, as reported also in [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF] in their study on a large number of sulfates. This shift is related to the influence of additional H 2 O molecules in the mineral structure, which modify the S-O bond length.

4-5-µm sulfate complex band

The intense and broad absorption band appearing in the 4-5 µm region, due to first order overtone and combinations of the fundamental SO 4 2-ν 3 vibration at 8-10 µm [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF], is the most characteristic and diagnostic feature of the sulfate minerals family in the Visible-Near-Infrared region below 5 µm. It can have different spectral shapes for different sulfates [START_REF] Omori | Infrared studies of saline sulfate minerals[END_REF][START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF]. In particular this feature is notably different in thénardite and mirabilite. In the anhydrous sample (fig. 5) the band extends between 4-4.9 µm, and is characterized by an interband peak in reflectance centered near 4.53 µm. The peak height appears to increase in reflectance (0.2-0.4) as the temperature decrease in the range 275-80K, at least for the 75-100-µm grain size, due to the narrowing of both components. In mirabilite (fig. 7) the band extends in the range 3.8-5.0 µm and is more asymmetric with the minimum positioned around 4.8 µm, although because of noisy data around 5 µm it an accurate determination of position was not possible. The main difference is the absence, in mirabilite, of the interband peak at 4.53 µm. An explanation for this difference could be the presence of many H 2 O molecules influencing S-O bonding in mirabilite, implying a broad range of vibration energies. Indeed in [START_REF] Cloutis | Faith Vilas: Detection and discrimination of sulfate minerals using reflectance spectroscopy[END_REF] H 2 O-bearing sulfates show broad absorptions in this range, while anhydrous or OHbearing sulfates (barite, anglesite, anhydrite) have bands with many well-resolved minima.

Effect of grain size

The grain size influences a number of absorption bands and spectral parameters. Differences between spectra among the grain sizes are visible in fig. 3. In thénardite 3.0, 3.68 and 3.86 µm bands, band depth and area increase for larger grain sizes at a given temperature. Moreover the 3.0-µm band is shifted at longer wavelengths (2.99 µm) for the medium grain size, while it is shifted at shorter wavelengths (2.97 µm) for the smallest grain size. Regarding the band in the 4-5 µm region in thénardite, the spectral shape changes gradually (fig. 4): with increasing grain size the reflection peak shifts towards longer wavelengths, from roughly 4.50 µm (g.s. 36-50 µm) to 4.52 µm (g.s. 75-100 µm) to 4.54 µm (g.s. 125-150 µm). Moreover, the bottom of the band, on the left and right of the interband peak, is characterized by a negative slope in the grain size 36-50 µm. As the grain size becomes larger, the slope decreases and the band becomes flatter, due to saturation. In mirabilite, the band depth (for a given temperature) increases monotonously with grain size for the 1.20 and 1.78 µm band, being minimum for the smaller grains and maximum for the largest grain size. For the bands at 1.46 and 2.47 µm the band depth assumes the maximum value for the intermediate grain size. The 3-µm band complex shows the maximum depth for the smallest grain size. This can be explained by taking into account that weak absorption bands (i.e. 1.20 and 1.78 µm) tend to saturate at greater grain sizes than stronger bands (i.e. 1.46, 2.47 and 3.0 µm): that is the grain size of optimal band depth reduces as the absorption gets stronger [START_REF] Hapke | Theory of Reflectance and Emittance Spectroscopy[END_REF][START_REF] Harloff | Near-infrared reflectance spectroscopy of bulk analog materials for planetary crust[END_REF].

Extended-Visible parameters vs Temperature

The Visible region of mirabilite spectra has also been studied; spectra in the Visible range are displayed in fig. 10 without any additional offset along Y-axis. Parameters such as slope, reflectance factor and area are shown in fig. 11 as functions of temperature. All parameters show changes with grain size and temperature. Two different slopes have been retrieved and compared with temperature and other spectral parameters: the visslope-1 (0.40-0.54 µm) and vis-slope-2 (0.60-0.92 µm). The slope-1 is generally positive (red) and reaches a positive maximum value. The slope-2 is negative (blue) and reaches a minimum (maximum absolute value). The slope-1 is only shown for the 75-100 and 125-150 µm grain size (fig. 11A), because in the fine grain size it does not change appreciably. The change with temperature is characterized by a maximum value at about 150-160K. The slope-2 (fig. 11B) has a behavior that is similar for the three grain sizes, reaching one or two minima (negative) in the 100-180K range. The slope-1 appears to be positively correlated with the 3-µm band of water (fig. 11C). The reflectance at 0.6 µm has been determined, as well as the maximum reflectance value in the 0.4-0.9-µm range and its wavelength position. The value of maximum reflectance is shown in fig. 11D as a function of temperature. For all the grain sizes, as temperature drops down the reflectance increases, reaching a maximum near 150-160K. The reflectance is minimum for the lowest and highest temperatures. The wavelength position versus temperature of this reflectance peak is displayed in fig. 11E: except for the room temperature value, the peak has its maximum shift towards longer wavelengths at 140-160K. Finally, for each temperature and grain size, the area comprised between the spectral data and a line joining the wavelengths 0.4-0.7 µm has been computed: this is a measure of the curvature of spectra in the VIS region. This parameter again appears to be maximum at 160K and minimum at the lowest and highest temperatures.

Implication for Europa -JUICE/MAJIS and Europa Clipper/MISE

Among non-water-ice compounds thought to exist on the surfaces of the icy Jovian satellites, hydrated salt minerals were first proposed to exist as a by-product of endogenic processes (McCord et al., 1998a(McCord et al., , 1998b[START_REF] Mccord | Hydrated salt minerals on Europa's Surface from the Galileo near-infrared mapping spectrometer (NIMS) investigation[END_REF][START_REF] Mccord | Brines exposed to Europa surface conditions[END_REF]. While the agreement with nearinfrared spectral observations of dark terrains on Europa is indeed better for highly hydrated salts than for salts of lower hydration states, none of these materials alone can account for all of the observed spectral character [START_REF] Dalton | Spectral comparison of heavily hydrated salts with disrupted terrains on Europa[END_REF]. Europa and Ganymede's non-ice material appears to be a complex mixture of sulfate hydrates and other materials [START_REF] Mccord | Hydrated salt minerals on Europa's Surface from the Galileo near-infrared mapping spectrometer (NIMS) investigation[END_REF]. Best fits for non-icy terrains were initially found to be provided by mixtures of hydrated sodium sulfates, hydrated magnesium sulfates, which are typical endogenous products, and sulfuric acid hydrate, which instead is a product of radiolysis [START_REF] Carlson | Sulfuric acid on Europa and the radiolytic sulfur cycle[END_REF][START_REF] Dalton | Linear mixture modeling of Europa's non-ice material based on cryogenic laboratory spectroscopy[END_REF][START_REF] Shirley | Europa's ridged plains and smooth low albedo plains: Distinctive compositions and compositional gradients at the leading side-trailing side boundary[END_REF]. In recent times, the traditional hypothesis of the presence of sulfate salts on the surface of Europa has been challenged as Mg-bearing chlorinated species (chloride, chlorate, and perchlorate) have been found to provide improved spectral fits in the NIR range [START_REF] Ligier | VLT/SINFONI Observations of Europa: New Insights into the Surface Composition[END_REF]. Even more recently, on the basis of HST observations obtained in the visible range, sodium chloride (NaCl) was suggested to be the main spectral endmember on the surface of Europa, implying a NaCl-rich ocean [START_REF] Trumbo | Sodium chloride on the surface of Europa[END_REF]. Despite these apparently diverging results, as a matter of fact the current chemical composition of the surfaces of Europa and Ganymede is expected to reflect, as far as the endogenous component is concerned, the composition of the subsurface ocean lying in the interiors of these moons. At least in the case of Europa, various salt minerals may form from direct contact of liquid water with a silicate mantle found on the ocean's floor. In this scenario, it is plausible to argue that several soluble salts might actually coexist within the ocean as well as on the surface, as a result of the transient water plumes that have been discovered over the last years [START_REF] Roth | Transient Water Vapor at Europa's South Pole[END_REF][START_REF] Sparks | Probing for evidence of plumes on Europa with HST/STIS[END_REF][START_REF] Paganini | A measurement of water vapour amid a largely quiescent environment on Europa[END_REF]. The different molecular weight of the salt minerals can then account for a potential stratified compositional sequence that is observed in the uppermost surface layer. In the case of Ganymede, no ongoing activity has been observed so far, and theoretical models of the interior seem to rule out a direct, constant and vigorous exchange between the internal liquid layer and a silicate mantle. Nonetheless, optical images show evidence for resurfacing and terrains with relatively recent geologic age, with grooves from which liquid water could have found its way out in the past. In compositional terms, this is in agreement with both NIR hyperspectral data returned by the NIMS spectrometer (McCord et al., 1998a), and with recent Earth-based observations [START_REF] Ligier | Surface composition and properties of Ganymede: Updates from ground-based observations with the near-infrared imaging spectrometer SINFONI/VLT/ESO[END_REF]. These results ultimately suggest that Ganymede may have a surface composition close to that of Europa, with exogenous effects that are mitigated both by the larger distance from Jupiter and by the presence of an intrinsic magnetic field that protects the surface from high energy charged particles at low latitudes. The primary scientific objective of the imaging spectrometers carried onboard the NASA Europa Clipper and ESA JUICE spacecrafts is to identify and map the composition of nonwater-ice materials on the surfaces of the icy Galilean satellites, with an emphasis on Europa and Ganymede, respectively. Separating endogenous and exogenic products, the latter being a constant byproduct of Jupiter's harsh radiation environment, is also a major objective. For this reason, it is essential to build a database of laboratory spectra measured in the same spectral range that will be covered by those instruments, and in a range of cryogenic temperature representative of those planetary surfaces. While our experiments do not take into account exogenic effects caused by radiation, the information deriving from the dependence of the spectral profiles on parameters such as temperature and grain size proves to be crucial in applying spectral unmixing models to the hyperspectral data sets that will be acquired, ultimately allowing both the identification of the most plausible chemical species and the estimation of their physical state. Following this idea and using the same laboratory setup, in previous works we had already analyzed: 1) hydrated magnesium sulfates (De Angelis et al., 2017), and 2) hydrated and anhydrous sodium carbonates [START_REF] De Angelis | NIR reflectance spectroscopy of hydrated and anhydrous sodium carbonates at different temperatures[END_REF]. In this regard, the present work represents the third set of mineral salts for which we took spectral profiles that may prove useful in view of future interpretation of data acquired by these spectrometers. Among the sodium sulfates considered here, the anhydrous form thénardite is very hygroscopic and requires a very dry environment to exist. Thus it is not expected on the surfaces of the icy satellites, which are dominated by water ice. Nevertheless the possibility exists that thénardite could be formed as secondary product after irradiation and dehydration of mirabilite, and persist for some time on the surface of Europa; such a mechanism, i.e. dehydration of salts into lower hydrated forms, has been shown to occur on Europa for Clbearing species [START_REF] Thomas | Composition and Evolution of Frozen Chloride Brines under the Surface Conditions of Europa[END_REF]. It was chosen only as a reference compared to a stable hydrated form such as mirabilite, which instead is among the chemical species potentially expected to occur on the icy satellites. However, in mirabilite the spectral signatures are largely dominated by combinations and overtones of the water molecules that make up the mineral. Therefore, thénardite served above all to highlight the absorptions due to the SO 4 2-ion and to facilitate our assignment of the observed spectral signatures in mirabilite. The MAJIS spectrometer onboard the ESA JUICE mission covers the overall spectral range 0.50-5.54 µm, with an average spectral sampling step of 3.7 nm/band between 0.50 and of 2.35 µm and 6.5 nm/band between 2.25 and 5.54 µm [START_REF] Piccioni | Scientific goals and technical challenges of the MAJIS imaging spectrometer for the JUICE mission[END_REF]. Consequently, the spectral sensitivity range is largely comparable to that of the SHINE facility that we used for this work, while the expected sampling step of MAJIS is better. On the other hand, the strong absorption of water ice on Europa and Ganymede results in very low reflectance beyond 2.7 µm, creating significant observational and signal-to-noise challenges in that region for infrared spectrometers. In this regard, the identification of the diagnostic features of mirabilite at 3.8 and 4.6 µm could be more challenging than the identification of other diagnostic features located at at 1.78, 2.18 µm and 2.47 µm, which, despite their variable strength (medium to very weak, see Table 1), are located in a spectral region favored by a larger signal coming from the target. On the other hand, a SNR > 30 should be large enough to reveal all these spectral signatures, especially those located beyond 2.7 µm, which could therefore guarantee a safe identification of the presence of pure deposits of mirabilite, if any, separating them from potential local exposures of other salt minerals. The variation in the slope of the visible spectra of mirabilite as a function of temperature, which we observed in laboratory, is also preparatory for the interpretation of the spectra of the icy Galilean satellites that will be acquired by MAJIS in the visual range 0.5-1.0 µm. Indeed, this highlights the need of including this spectral range to achieve a comprehensive evaluation of the surface composition, and it also emphasizes the science case of using multispectral images with JUICE in the visual range up to 1 µm to highlight compositional variations potentially linked also to the presence of this mineral on the surface. The Mapping Imaging Spectrometer for Europa (MISE) instrument [START_REF] Blaney | The Europa Clipper Mapping Imaging Spectrometer For Europa (Mise): Using Compositional Mapping To Understand Europa[END_REF] onboard NASA spacecraft Europa Clipper will observe the icy satellite in the 0.8-5 µm spectral range, with 10 nm spectral sampling and 25 m/px at a distance of 100 km. The MISE spectrometer has the capability to detect all the described spectral features relative to thénardite and mirabilite. Concerning thénardite absorption features at 3.1, 3.24, 3.68 and 3.86 µm, with FWHMs of about 30-50 nm, could be easily detected. The detector cutoff at 5 µm could allow observing the 4.6-µm sulfate band, although presumably with some noise in the long-wavelength edge. Regarding mirabilite all the absorption feature in this range have FWHMs well above the instrument resolution and are detectable. The fine structure arising at low temperatures in bands such as 1.46 and 2.47 µm should also be resolved. The long-wavelength wing of 4.6-µm sulfate band could be detected but noisy. Mirabilite bands at 1.20 and 3.80 µm display the largest shifts with temperature, being of the order of >10 nm and >20 nm, towards longer and shorter wavelengths, respectively. Such shifts are potentially above the detection limit of both MAJIS and MISE instruments. At about 100K these two bands are located near 1.22 and 3.77 µm. Using in conjunction band position and band depth, for example of the 3.80 µm feature, the grain size can also be estimated. At 100K this feature would have a band depth of about 0.02 for smaller grain sizes (<50 µm), while it would be about 0.05 for larger grains (>125 µm). Monitoring of changes in VIS slope over time can also be useful in order to detect temperature variations with time.

Implication for Mars missions

Missions planned to explore the Mars surface in the next future (NASA/Mars 2020 and ESA-RosCosmos/ExoMars 2022) host optical cameras and infrared spectrometers that are in principle capable to detect thénardite and mirabilite. Mastcam-Z on Mars 2020 Rover [START_REF] Bell | The Mars 2020 Rover Mast Camera Zoom (Mastcam-Z) Multispectral[END_REF] will observe the surface in the extended visible region up to 1 µm, thus with the capability of detect water combination/overtone bands related to the presence of hydrated minerals and eventually also mirabilite [START_REF] Rice | Silica-rich deposits and hydrated minerals at Gusev Crater, Mars: Vis-NIR spectral characterization and regional mapping[END_REF]. Ma_MISS spectrometer (De Sanctis et al., 2017) inside the drill of the ExoMars 2022 rover has the potentiality of detect hydrated minerals in the Mars subsurface if present. In particular the mirabilite bands at 1, 1.2, 1.46 and 1.78 µm fall in the sensitivity range of this instrument. The ISEM spectrometer [START_REF] Korablev | Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover[END_REF] onboard ExoMars rover, with its 1.1-3.3 µm range, will have the capability of measure mirabilite hydration bands from the 1.2 to the 3µm band, although this last would be truncated, and the thénardite bands at 3.1-3.24 µm.

Conclusions

Visible and near-infrared spectra of the anhydrous sodium sulfate (thénardite) and the decahydrated phase (mirabilite) are characterized by different patterns of absorption features, varying with temperature changes in different ways. Thénardite has a flat and nearly featureless spectrum up to 2.6 µm. Apart from a 3-µm band due to adsorbed water, diagnostic sulfate bands occur at 3.68, 3.86 and especially at 4.6 µm. Bands at 3.1 and 3.24 µm could be also diagnostic of thénardite. A feature appearing at 3.42-3.5 µm can also be tentatively attribute to sulfate, although the position is also consistent with C-H vibration. The 4.6-µm large doublet is characteristic of sulfates in the VIS-NIR region. In thénardite this strong band is characterized by an interband peak near 4.5 µm, separating two minima. The band shape does not seem to vary appreciably with temperature, although it gradually changes with grain size, becoming flatter and with decreasing slope (in absolute value) as the grain size increases. Spectra of mirabilite are characterized by a large number of water related features, occurring near 1, 1.2, 1.46, 1.78, 1.95, 2.47, 3 µm, and by at least two features due to sulfate at 3.8 and 4.6 µm. The 1.78-µm feature is reported also in other hydrated sulfates.

In mirabilite the SO 4 2-first overtone band occurring at 4.6 µm is notably different from the anhydrous phase, being characterized by the absence of the interband peak near 4.5 µm, and with the minimum shifted towards longer wavelengths. Due to the high hydration state this band is much more broadened in mirabilite. Water-related features show generally shifts towards longer wavelengths as the temperature drops down, while 1.78, 2.47 and 3.8-µm bands slightly shifts in the opposite sense, i.e. towards shorter wavelengths. The visible region up to 1.1 µm in the spectra of mirabilite, being characterized by a spectral slope that correlates with temperature changes, is also of interest with the aim of interpreting remote sensing data from future missions such as JUICE and Europa Clipper. Although recently the general idea about the surface composition of Europa and Ganymede has changed, pointing to a greater complexity and variety in terms of mineral species present on these bodies, nevertheless our dataset is important in order to characterize also this type of compounds, given that mirabilite could be present as component in more complex mixtures.

Fig. 1 .

 1 Fig.1. Reflectance spectra of anhydrous sodium sulfate (thénardite), measured at different temperatures in the range 80-298K and in three grain sizes. Temperatures decrease from top to bottom. Top panel: "fine" grain size (36-50 µm). Middle panel: "intermediate" grain size (75-100 µm). Bottom panel: "coarse" grain size (125-150 µm). Spectra above 80K are shifted vertically by 0.1 in reflectance for clarity.

Fig. 2 .

 2 Fig. 2. Reflectance spectra of decahydrated sodium sulfate (mirabilite), measured at different temperatures in the range 80-298K and in three grain sizes. Temperatures decrease from top to bottom. Top panel: "fine" grain size (36-50 µm). Middle panel: "intermediate" grain size (75-100 µm). Bottom panel: "coarse" grain size (125-150 µm). Spectra above 80K are shifted vertically by 0.1 in reflectance for clarity.

Fig. 3 .

 3 Fig. 3. Reflectance spectra of thénardite (top) and mirabilite (bottom) for the three analyzed grain sizes. For each grain size two temperatures are shown, 80K and 298K.

Fig. 4 .

 4 Fig. 4. Continuum removed bands for thénardite (anhydrous sodium sulfate), in the spectral range 3-4 µm. The procedure for continuum removal is described in Section 2.3. Here we show only the spectra for the "fine" grain size (36-50 µm).

Fig. 5 .

 5 Fig.5. Continuum removed 4.6-µm band doublet for thénardite (anhydrous sodium sulfate). The procedure for continuum removal is described in Section 2.3. We compare the shape of the band for all three grain sizes.

Fig. 6 .

 6 Fig. 6. Anhydrous sodium sulfate (thénardite): 3-µm band spectral parameters, as a function of temperature. The four panels respectively report the trend of: band center, band depth, band area and band width. The method used to compute these parameters is described in Section 2.3. In each panel the symbols indicate the different grain sizes: circle for the "fine" grain size (36-50 µm), square for the "intermediate" grain size (75-100 µm), and triangle for the "coarse" grain size (125-150 µm).

Fig. 7 .

 7 Fig. 7. Continuum-removed bands for mirabilite (sodium sulfate decahydrate). The method used to compute these parameters is described in Section 2.3. Here we show the fine grain size (36-50 µm) spectra.

Fig. 8 .

 8 Fig.8. Sodium sulfate decahydrate (mirabilite): 1.20 and 1.46-µm band spectral parameters as a function of temperature. We report the parameters: band center, band depth, band area, and band width. The method used to compute these parameters is described in Section 2.3. In each panel the symbols indicate the different grain sizes: circle for the "fine" grain size (36-50 µm), square for the "intermediate" grain size (75-100 µm), and triangle for the "coarse" grain size (125-150 µm).

Fig. 9 .

 9 Fig.9. Sodium sulfate decahydrate (mirabilite): 1.78 and 2.47-µm band spectral parameters, as a function of temperature. We display the spectral parameters: band center, band depth, band area, and band width. The method used to compute these parameters is described in Section 2.3. In each panel the symbols indicate the different grain sizes: circle for the "fine" grain size (36-50 µm), square for the "intermediate" grain size (75-100 µm), and triangle for the "coarse" grain size (125-150 µm).

Fig. 10 .

 10 Fig.10. Mirabilite. Visible Near-IR spectra (0.4-1.1 µm).

Fig. 11 .

 11 Fig.11. Mirabilite Visible parameters: slopes, reflectance, area. The retrieved parameters are described in the section above.

  Tab.2. Band parameters and their dependence on temperature for thénardite and mirabilite. Only the bands analyzed are shown. The vibration mode attribution of each band is listed in tab.1. B C vs

	Sample	B (µm)	BC vs T	ΔBC	BD vs T	ΔBD	BA vs T	ΔBA	BW vs T	ΔBW
	Na2SO4	2.9-3.0	è (300-160K)	+40	é	40%	é	20%	ê.	10%
			ç (160-80K)	-20	ê		ê
		3.1	-	<<5	é	40%	é	20%	ê.	10%
					ê		ê
		3.24	ç	<10	é	25%	é	30%	ê	10%
					ê		ê
		3.42 (I)-3.5 (II)	-	<<5	é	10%	é	30%	ê	10%
					ê		ê
		3.68	-	<<5	é	15%	é	20%	-
		3.86	-	<<5	é	20%	é	20%	-
		4.0-4.9	-		-		-		-
	Na2SO4 10H2O	1.2	è	+12	é	20%	é	15%	ê	10%
		1.46	è	+7	é	10%	é	15%	é	10%
									ê
		1.78	ç	-8	é	35%	é	40%	é	10%
		1.95	è	+8	é	5%	é	10%	é	10%
		2.47	ç	-4	é	15%	é	30%	é	15%
		3.0	è (300-160K)	>50	é	30%	ê	20%	ê	20%
			ç (160-80K)		ê
		3.8	ç	-30	é	50-90%	é	80%	é	40%
		4.0-4.9	-		-		-		-

T: Left arrow: shift towards shorter wavelengths; Right arrow: shift towards longer wavelengths. The shifts (Δ) are expressed in nm for band center; for depth, area and width as % variation. The up/down changes in parameters (B D/A/W vs T columns) are for decreasing temperature. When both up and down arrows are present, they are relative to the temperature ranges 300-160K and 160-80K.

Acknowledgements

The set of measurements described in this work is the outcome of the research project: "Characterization of Na-sulfates at Cold Planetary Conditions" (PI: Dr. Federico Tosi, Co-I Dr. Simone De Angelis), selected and funded in June 2017 in the framework of the European Union's Horizon 2020 Research Infrastructure (RI) programme (http://www.europlanet-2020-ri.eu), under grant agreement No. 654208. This work was partly supported by the Italian Space Agency (ASI), ASI-INAF grant 2013-056-R.O., and by the Centre National d'Etude Spatiale (CNES). We also wish to thank J.L.Bishop and an anonymous reviewer for their precious comments and suggestions.

On-line data

The complete sets of data (De Angelis et al., 2018a[START_REF] Angelis | VNIR reflectance spectra of Mirabilite (Na 2 SO 4 10H 2 O) with 3 different grain sizes and at variable temperature (80-298K). SSHADE/REFL_SLAB+CSS[END_REF] presented in this paper are available online upon publication of this paper in the REFL_SLAB and CSS databases of the SSHADE database infrastructure (https://vwww.sshade.eu): https://doi.org/10.26302/SSHADE/EXPERIMENT_CC_20180427_001 and https://doi.org/10.26302/SSHADE/EXPERIMENT_CC_20180428_002.


Objective 1: Develop a sustainable and scalable operating

Executive Summary

Task 5.1 aims to analyse the different demonstrators in light of the process necessary to implement their DMPs and to propose a categorization based on users' needs. This effort will provide input to WP1 with respect to needs in terms of experts and resources across ELIXIR Nodes (Task 1.3, Business plans). It is expected that some of them will be generic whereas others will be very specific to projects, which is an important factor for establishing a strategy towards the sustainability of such a service in all its diversity.

D5.1 therefore describes the needs in terms of DMP of the demonstrator use-cases and proposes a project categorization from the point of view of:

-Area of expertise -The resources they use / toolkit -Training needs

The first challenge was to develop a method to describe the needs of the users and their current practices in terms of data management as a prerequisite to the development of an adequate toolkit. The method adopted with the guidance of WP2 and WP3 relied on the description of users stories, and scenarios for different types of personas. In addition, a table was also developed to collect knowledge on the current practices and existing resources in terms of data management with guidance from WP1 and WP3. The six demonstrator use-cases are divided into two waves to facilitate having a broad diversity of data types, potential users and variable expertise and, at the same time, have first mature demonstrator use-cases that can start providing input to other WPs in the projects. The Plant and the Marine Metagenomics demonstrator use-cases were used as testers for the method developed as they are the two selected ones for the first wave. Federated access to human genomics data belongs to the second wave of demonstrator use-cases. However, considering its broad reach, it has been partially developed for this deliverable.

User stories and scenarios with personas were developed by WP5 partners on the Plant, Marine metagenomics and Federated access to human genomics data: GDPR use-cases.

The table on existing tools and resources was also filled in by WP5 partners and target interviews of researchers for some of the demonstrator use-cases. Additional input was sought from the ELIXIR communities for the demonstrator use-cases mentioned before.

The main aspect used to classify a new use-case is the type of biological material linked to the data that links to many specific requirements, e.g. legal and scientific metadata. The second is the relation of the personas with the data, e.g. consumers/producers, and the type of data, including workflows, models, and the various types of experimental data.

The landscape analysis of the resources already available in relation with the demonstrator use-cases and the different stages of a data management plan, showed that the guidelines developed by WP1 are very useful to clarify the scope of these stages before filling such a survey.

The personas/users related to the use-cases are very diverse but always include the researchers in various positions, e.g. data consumer, data producer, data owner, PI writing a proposal, and the data curators. This will be further developed in collaboration with WP2.

Finally, the work achieved to deliver D5.1 facilitated the development of pages dedicated to the "domains" in the RDMKit website (https://rdmkit.elixir-europe.org/) for demonstrator use-case 1, 3, 4 and 6. In these pages, specific challenges linked with the demonstrator use-cases are highlighted, and dedicated resources to solve them are listed. These tools have also been flagged in bio.tools with the domain name.

Contribution toward project objectives

With this deliverable, the project has reached or the deliverable has contributed to the following objectives/key results:

Introduction

The overall goal of WP5 is to assess the capacity of ELIXIR and its national nodes to assist users' projects in implementing data management plans (DMPs) in their concrete projects at a EU scale. A set of six very diverse demonstrator use-cases will be addressed for this purpose.

As a first step, Task 5.1 aims to analyse the different demonstrators in light of the process necessary to implement their DMPs and to propose a categorization based on users' needs. This effort will provide input to WP1 with respect to needs in terms of experts and resources across ELIXIR Nodes (Task 1.3, Business plans). It is expected that some of them will be generic whereas others will be very specific to projects, which is an important factor for establishing a strategy towards the sustainability of such a service in all its diversity.

D5.1 therefore describes the needs in terms of DMP of the demonstrator use-cases and proposes a project categorization from that point of view:

-Area of expertise -The resources they use/toolkit -Training needs

In addition to the initial plans, we decided to make a first mapping of resources (expertise, tools, training) that are already identified across ELIXIR's nodes and possibly beyond to support these needs in the light of their specialization to certain areas of research or, on the contrary, their genericity. This will improve the interactions with WP3 (development of the toolkit) and WP2 (development of training). Harmonised/benchmarked workflows , MIAME, BioSamples. ○ Key Deposition databases, standards and Interoperability resources: ChEMBL, OLS, Transnational access to complex data, terminology mappings (OxO). 6. FAIR organisation of biomolecular simulation information (2nd wave; ES, SE).

Common Data management plans for the marine metagenomics Community

○ Data types & Challenge: long coordinate files containing the evolution of 3D positions of atoms of the system across time; output of a wide variety of analysis tools applied to raw data, metadata describing system setup and the simulation parameters. Simulation data is typically stored locally in an undocumented manner, without any external curation and lacking associated metadata required for their reusability. ○ Key Deposition databases, standards and Interoperability resources: Some initial attempts in the generation of usable ontologies (UMM, BigNASim).

Description of work accomplished

Development of methods and templates to collect more information about the demonstrator use-cases

The first challenge was to develop a method to describe the needs of the users on their current practices in terms of data management as a prerequisite to the development of an adequate toolkit. The six demonstrator use-cases are divided into two waves to facilitate having a broad diversity of data types, potential users and variable expertise and at the same time have first mature demonstrator use-cases that can start providing input to other WPs in the projects. In that sense, the Plant and the Marine Metagenomics use-cases were used as testers for the method developed as they are the two selected ones for the first wave. Federated access to human genomics data belongs to the second wave. However, considering its broad reach, it has been partially developed for this deliverable. Persona are the characters who will appear in our user stories. They represent our users and makers of the toolkits, the data steward experts and trainers and others. Many (but now all) will be drawn from the Stakeholders.

User Scenarios are fictitious "Alice and Bob" stories of accomplishing an action or goal via the Toolkit. The characters in the scenario are drawn from the Persona.

User Stories are high level requirements that could be translated later into the technical requirements for the toolkit and follow a strict template. To complete the description, scenarios involving personas were also described: : see ELIXIR-CONVERGE_Demonstrator_Scenarios_v14 . The description of the scenarios was easier and more natural than the table proposed by GO FAIR. In addition, it allows to describe the context in which the personas interact, absent in the GO FAIR template.

Description of the resources and expertises in relation with the demonstrator use-cases

In addition to the description of the users needs, WP5 decided also to collect information on existing tools and resources (training, expertises) that are available in the ELIXIR infrastructure in relation to the demonstrator use-cases to the knowledge of the partners.

The table to collect this information was developed building on the work done in M3.1 and D1.1: ELIXIR_CONVERGE_Demonstrator_resources_v15

Method for collecting the data

-The user stories and scenarios with personas were developed by WP5 partners with initial guidance from WP2 and WP3 on the different categories of personas. -The table on existing tools and resources was also filled by WP5 partners and target interviews of researchers for some demonstrator use-cases. -Additional input was sought from the ELIXIR communities for demonstrator use-case 1, 3 and 4.

Results

The personas and their requirements

Users stories and scenarios have been developed for three use cases:

-Demonstrator use-case 1: Harmonised FAIR plant genotype & phenotype data management toolkit for Europe -Demonstrator use-case 3: Common Data management plans for the marine metagenomics Community -Demonstrator use-case 4: Federated access to human genomics data: GDPR A scenario describes the needs of demonstrator use-case 6: FAIR organisation of biomolecular simulation information.

The data consumers

All the demonstrator use-cases are addressing data consumers who need to find specific categories of scientific data (e.g. human genomic data per cohort) and to be able to reuse it in new analyses. The common personas for use-cases are:

-the researchers and the students that have similar needs: finding all the relevant data, elements of quality about the datasets, possibility to sort it by relevant categories and reference tools for analysis. Note that the main persona of demonstrator use-case 6, which deals with modelling, is a consumer of public data.

-the data archive managers: make statistics about the use of their stewarded data to improve their services.

Demonstrator use-case 1 cited also the trainers/teachers that have similar needs to the researchers and students to develop their training courses: reference datasets and pipelines and knowledge about the most relevant data archives.

The two last data consumers cited by demonstrator use-cases 1 and 3 are interested in the data management plan:

-the funders who want to measure their impact through statistics on the data set produced by the projects they funded and their citation or number of downloads. They also might be interested to make statistics on the DMPs: what are the shared practices, tools and resources cited.

-the managers of facilities or laboratories who want to help their users to comply with good practices in terms of data management and data analysis along the whole process.

The data producers

All demonstrator use-cases cite the researchers and post doc/PhD students as data producers. They have very similar needs: they want to know how to best collect their data and metadata, to store it along its life cycle, and finally where to publish it. In addition, researchers want to know how to formalize a DMP for their projects.

Demonstrator use-cases 1 and 3 cite the lab/facility managers that also want to implement the FAIR principles on the data they produce, e.g. genomic or phenotyping facilities, or to support and guide researchers for their needs in terms of data management and data analysis.

In case of sensitive data (Demonstrator use-case 4), cohorts owners have specific activities to deal with requests of data and Trusted Third Parties, for the use of sensitive data.

The workflow productors

This category is not included in Demonstrator use-case 1 and has different predominance in the other use cases.

-Demonstrator use-case 2: the researchers that create workflows want to store and document them to make them reusable by others. They also want to benchmark -Demonstrator use-case 6 is mainly about workflows (models). Its main persona, the modeller, needs a platform to store their models and link them to the data.

Data owners/managers/controllers

This category is very important in Demonstrator use-case 4 in relation to sensitive human data. The data owners need to ensure that the GDPR rules are fulfilled and to measure the legal risks associated with their research projects. To make this possible, data managers as data custodians must ensure that the data is under strict control access along the whole data life cycle.

For the other use-cases, researchers need guidance to associate the right licence to their data and facilities/institutions on policies about data ownership and data licencing.

Data curators

-All demonstrator use-cases cite the need for automatic checks of metadata (presence) and format compliance. -Demonstrator use-case 4 must process the metadata in relation with its sensitivity.

-Demonstrator use-case 3 needs to develop quality checks on the data and the metadata. -Up-to-date guidelines for properly maintaining and interconnecting metadata, e.g. to contribute towards the FAIRness of the data/metadata, are needed for all use-cases.

Conclusions

The specifications of the demonstrator use-cases can be linked:

-to the biological material they deal with, its associated metadata capturing method, the knowledge about the environment in which it was sampled, specific identifiers and privacy management. 1 1 use-case 6, the main data is the statistical model derived from the original data using advanced simulation techniques. -to the phases of the data management plan they address (see table 1): all the demonstrator use-cases address the planning, preserving, sharing and reusing phases. However, there are other phases like analysing that are only relevant for some of them. The resources were described either as generic or as dedicated to a specific biological domain. It is interesting to see that there are already a significant number of resources that can be leveraged to address the demonstrator use-cases. Many of them are already registered in ELIXIR recognized registries like bio.tools and FAIRsharing. Importantly, key resources are specifically distinguished as ELIXIR Core Data Resources and/or Deposition Resources so the scientific community can trust them for gaining access to the knowledge available there and/or deposit their biological data for archiving and further sharing and reuse. Some of those resources, e.g. EGA, allows a fine-grained control of who accesses Some training courses and materials have been developed in particular for the management of sensitive human data, data management in general and standardization of plant phenotyping data. As we have seen in the work on the personas/users of the demonstrator use-cases, the researcher persona is always included in various positions, e.g., data consumer, data producer, data owner, PI writing a proposal, training. Therefore, we can say this category of persona will be particularly important. Also, a common terminology across the whole project is being developed, e.g. an extended and revised definition of personas, to allow generating fully coherent materials, best practices and guidelines.

Finally, a first round of identification of nodes' expertise needed to support the demonstrator use-case is available. This landscape is far from comprehensive and requires deep survey within ELIXIR nodes to move forward in its completion.

Conclusions

This is the first deliverable produced in the context of ELIXIR-CONVERGE WP5. As such, it has contributed to deepening the understanding of the pre-selected demonstrator use-cases. Selected use-cases represent a broad diversity of data types, with many associated challenges as well as bring together different sets of users roles, each of them with their own needs and expectations. The use of two differentiated waves of demonstrator use-cases has allowed us to rapidly move forward with some of them. On the contrary, the level of detail is at the moment differently among use-cases. As we progress in the project, and building in the initial experiences, we expect that those differences will progressively disappear.

The method implemented to describe the demonstrator use-cases in detail has been efficient to isolate the specific context of each case, and to identify specific tools/resources in relation with the use-cases that can be used for data management. Importantly, it has become clear that demonstrators will not cover all areas of the research data life cycle. This finding was not foreseen at the time of selecting them and is a direct product of the interactions with other WPs in the project.

The main aspect used to classify a new use case is the type of biological material linked to the data/metadata. Data/metadata is then linked to specific requirements and considerations, e.g. legal, use of ontologies, access mechanisms. The second is the relation of the personas with the research data associated to each demonstrator use-case, e.g. consumers/producers, and the type of data, including workflows, models, and the various types of experimental data.

The landscape analysis of the resources already available in relation with the demonstrator use-cases and the different stages of a data management plan showed that the guidelines developed by WP1 are very useful to clarify the scope of these stages before filling such a survey.

The personas/users related to the use-cases are very diverse but always include the researchers in various positions, e.g. data consumer, data producer, data owner, PI writing a proposal, and the data curators. This will be further developed in collaboration with WP2.

In close collaboration with WP3, we expect that demonstrator use-cases will provide feedback on the existing general knowledge model for research data management. Such feedback will set the foundations to propose specific extensions to the general knowledge model. Such extensions, potentially one per demonstrator, will allow researchers and data stewards and managers to have a greater level of detail when elaborating their data management plans.

Impact

The present work has allowed us to develop dedicated pages to the "Your domain" in the RDMKit website (https://rdmkit.elixir-europe.org/) for demonstrator use-case 1, 3 , 4 and 6. In these pages, specific challenges linked with the demonstrator use-cases are highlighted, and dedicated resources to solve them are listed. These tools have also been flagged in bio.tools with the domain name. This categorization will allow researchers and data stewards that work in these particular domains to be able to find solutions to their data management problems in an easier and faster way. This work not only had an impact across ELIXIR-CONVERGE, it also allowed the different demonstrator use-cases to be aware of their needs in terms of data management and to be able to categorize them so that they will be able to get the correct support by experts from each expertise.

  (1st wave; FR, DE, HU, IT, NO, PT, UK). ○ Data types & Challenge: Large Metagenomics datasets including whole metagenomes shotgun data, metagenome assembled genome data, metatranscriptome, metabarcoding data ○ Key Deposition databases, standards and Interoperability resources: Drive implementation of community standards across ELIXIR Nodes 1 4. Federated access to human genomics data: GDPR (2nd wave; FI, FR, GR, IT, LU, NO, ES, SE, CH). ○ Data types & Challenge: A typical ELIXIR Community member would be a research institute/medical centre that is willing to share their research data, but doing so under more restrictive conditions than general research reuse. Reusability of sensitive data in particular requires special effort from data users as well as data providers in the context of GDPR and its country-specific implementation in context of the 1M Genomes Declaration. ○ Key Deposition databases, standards and Interoperability resources: Local EGA functionalities, Beacon, ELIXIR Beacon Network, Data Access Management tools, GDPR tools, ELIXIR AAI, GA4GH standards. 5. FAIR encoding and access to Toxicology data (2nd wave; DK, EMBL-EBI, ES). ○ Data types & Challenge: Chemical structures, pharmacological data, toxicological data, data from clinical trials, information on drug side-effects, pharmacovigilance data, etc.

4. 1 . 1

 11 Users needs in relation with the demonstrator use-cases WP5 first developed user stories and scenarios involving different types of personas covering each demonstrator use-case. This method was proposed by Carole Goble (WP3) and Munazah Andrabi (WP3) who provided some documents of reference and definitions (see box 1). User stories were collected using a template developed by the GO FAIR initiative: Copy of Stocktaking GO FAIR Discovery IN -Use cases, infrastructure -for publication 2 2 https://docs.google.com/spreadsheets/d/1qK8sNP-zL9wVOWMrsX8dv2Tv5oia4sKk4pjLKBM9KMA/edit#gid =0 This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. Box 1 Stakeholders identifies those organisations and people who contribute to, impact or are impacted by CONVERGE toolkit training and experts.

  see also: https://en.wikipedia.org/wiki/Persona_(user_experience) User stories per personas were developed for three demonstrator use-cases: (see: ELIXIR-CONVERGE User Stories_v1 3 ) -Demonstrator use-case 1 -Harmonised FAIR plant genotype & phenotype data management -Demonstrator use-case 3 -Common Data management plans for the marine metagenomics Community -Demonstrator use-case 4 -Federated access to human genomics data: GDPR

  This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. 1 0 them. The managers of bioinformatics facilities want to know what resources are needed to run the workflows they install for their users. -Demonstrator use-case 4: the data stewards need workflows that ensure that privacy rules are fulfilled.

  Note that the three biological domains represented by Demonstrator use-cases 1, 2, and 4 are supported by ELIXIR communities. -to the demonstrator use-cases which are generic, in terms of biological domains, that are dealing with very different types of data. Demonstrator use-case 2 is about a specific type of omics data, e.g. epitranscriptomics, and the associated analysis tools at the moment are part of the associated metadata while in demonstrator This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.

  6 https://zenodo.org/record/4672600#.YG8m9BRKj0o This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.1 2 what data. Some of the resources listed along the different demonstrator use-cases are part of the ELIXIR Node Service Delivery plans, which contribute towards the sustainability of them.

  This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. 1 4

1. Harmonised FAIR plant genotype & phenotype data management toolkit for Europe (

  Six demonstrator use-cases are considered in WP5 in two waves and are described below. 1st wave; FR, DE, IT, PT, UK).

	○ Data types & Challenge: phenotyping data (tabular text, ISA-tab), genotyping
	data (SNP genotyping matrices in VCF either from genotyping arrays or GBS
	experiments, SSR type identification markers), includes data with restricted
	access.
	○ Key Deposition databases, standards and Interoperability resources: ENA,
	EVA, BioSamples, ISA-toolkit, MIAPPE, BrAPI, CropOntology.
	2

. Reproducible, comparable and FAIR Epitranscriptomics (2nd

  wave; IE, IL, IT, NO). ○ Data types & Challenge: Available high-throughput sequencing data sets, e.g.

deep RNA-seq of 25k samples; deep RNA-seq (MeRIP, miCLIP, ...) and Ribo-seq of 2.3k samples. ○ Key Deposition databases, standards and Interoperability resources:

Table 1 .

 1 Phases of a data management plan addressed by the ELIXIR-CONVERGE demonstrator use-cases (marked by an X).

	Demonstrator use-case	Biological domain	Planning Collect	Process Analyse Preserve	Share	Reuse
	1	specific	X	X	X	X	X
	5.2

Expertise, resources and training: ELIXIR's support and gaps

	To complete this first analysis, the WP5 partners have landscaped the current knowledge
	in terms of resources, training and expertise in relation with each demonstrator use-case
	and	with	each	phase	of	a	data	management	plan:	(see
	ELIXIR_CONVERGE_Demonstrator_resources_v1) 6

https://doi.org/10.1093/gigascience/gix047This project has received funding from the European Union's Horizon

Research and Innovation programme under grant agreement No 871075.

https://zenodo.org/record/4672588#.YG8lGRRKj0o 3 https://zenodo.org/record/4672569#.YG8i0xRKj0o This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.

https://zenodo.org/record/4672600#.YG8m9BRKj0o This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.

generic X X X X X X

specific X X X X X X X

specific X X X X X

generic X X X X X X

generic X X X X X

This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.1

0v3 Nikki Coutts (ELIXIR Hub) Circulated to the MB for final review before submission This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.

This method implemented to describe the demonstrator use-cases in detail has been efficient to isolate the specific context of each case, and to identify specific tools/resources in relation with the use-cases that can be used for data management. This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. Objective no. / Key Result no. Development of joint guidelines and common toolkit that are adopted into funder recommendations, with support available nationally and in Yes This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. 3 D5.1 Categorisation of the pilot projects local Development of a Node Impact Assessment Toolkit based on No This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075. 4 D5.1 Categorisation of the pilot projects RI-PATHS methodology. Key Result 4.2: Adoption of Impact assessment in ELIXIR Nodes, supported by Node coordinators network and feedback on applicability from dialogues with national funders. No private partnerships and industry outreach where open life-science data and services stimulate local bioeconomy No Key Result 4.4: Growth in reach, impact and engagement of stakeholder communication assessed by established ELIXIR Communications metrics No Key Result 4.5: Initiating and advancing discussions on Membership (EU and international) or strategic partnerships (international countries) following ELIXIR-CONVERGE workshops. No This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under grant agreement No 871075.

data stewards that connect national data centres and similar infrastructures and drive the development of interoperable solutions following international best practice, including