Jacques De Maillard
email: demaillard@cesdip.fr

Suzy Bott

Mark Mellor

Trajectories of reform in European police systems

Whether it is a matter of incentivizing partnerships, implementing performance indicators, developing regional police forces, or, on the contrary, nationalizing police organizations, the contemporary transformations of European police systems have rarely been analyzed from a comparative perspective. Looking at the reform trajectories of three different countries (one country with a Napoleonic tradition [France] and three countries that display moderate pluralism [England/Wales and the Netherlands]), this article shall identify the major trends of reform along two axes: centralization/decentralization and integration/fragmentation. It will highlight the juxtaposition of attempts at centralization with the conflicting implementation of new managerial reforms, as well as the different forms of politicization associated with issues of policing and delinquency.

1 This article benefited at various stages of its development from the input of Cyril Benoît, Mathilde Darley, Patrick Le Lidec, and Sebastian Roché, to whom I am very grateful. An earlier version was presented at the general seminar of the Sciences Po Centre d'études europénnes (CEE) (Center for European Studies) in October 2018, which generated a great deal of stimulating critical feedback. 2 The term "police system" refers to the set of relationships between public police forces, private or semi-public actors responsible for policing, and political actors or bodies responsible for the oversight of policing (Jacques de Maillard, Polices comparées [Paris: LGDJ-Lextenso, 2017]). In this article, I focus on public police forces-at the national, regional, or local level-and thus consider the structure of governance of public police forces.

3 Jean-Claude Monet (Polices et sociétés en Europe [Paris: La Documentation française, 1993], 91-3) provides a summary of the dangers associated with centralized systems ("the development of huge police forces, powerful union bureaucracies, [. . .] the growth of behemoths that are difficult to both manage and reform [. . .], a concern with 'covering their backs' [. . .], political policing") and decentralized systems ("extreme fragmentation going hand in hand with human and financial resources that are too limited to support the development of coherent policies for recruitment, training, and modern equipment"). Translator's note: Our translation.

On October 1, 2017, robust exchanges took place when the Catalan police force, the Mossos d'Esquadra, blocked officers from Spain's national force, the Guardia Civil, as they attempted to prevent people from entering polling stations to vote in the Catalan independence referendum. 1 These scenes publicly exposed a quiet transformation: under Spain's autonomous community system, Catalonia, like the Basque Country, has gradually developed its own regional police force with large numbers of wellequipped officers. Conversely, in Scotland and the Netherlands, regional police forces disappeared in 2013 and have been replaced by national organizations (Police Scotland and the Korps Nationale Politie respectively) in a move that observers would have thought impossible just a few years earlier. These two examples point to an important phenomenon that has been the subject of little systematic analysis: the diverse range of ways in which the levels of power are being reformed in contemporary police systems. 2 The challenge is a sizable one, as police forces have to resolve opposing pressures: the pressure to centralize in order to pool human and logistical resources against a background of budgetary constraints, but also to decentralize in order to tackle specific local issues; to cooperate in order to respond effectively to crime and terrorism, but also to hold onto information in order to protect sources. These demands thus pull the organization of police systems in opposite directions. 3 Taking a broader view, analyzing these developments from the perspective of a particular field of public policy contributes to research on contemporary administrative reforms, which are characterized by complex, interlinked logics of increased centralization (through the use of new managerialist tools and the politicization of appointments) and delegation (as a result of political decentralization). 4 A number of researchers have argued that efforts to streamline budgets, the pursuit of greater control over police organizations in a bid to increase the effectiveness of the fight against crime due to strong political pressure, and crises and scandals affecting police practices, have called into question the institutional arrangements of the past and resulted in the increased centralization of police systems. 5 This hypothesis of homogenization under external constraints is at odds with the equally widespread idea of the permanence of police command structures. In his comparative analysis of police forces, David H. Bayley sets out how the conditions in which states originally formed have an enduring effect on the main structural features of police systems, including their degree of centralization. 6 The basic idea, a cornerstone of historical institutionalism, is that "the preferences and choices of actors are pre-structured by institutional corridors established for the long term." 7 Police centralization, for example, was initially driven by resistance to state-building, 8 while peaceful relations between the center and the periphery favored the development of pluralistic police systems.

In this article, I will test these two hypotheses now prevalent in the academic literature-the overall trend toward centralization versus the permanence of the historically constituted diversity of police structures-by analyzing the trajectories of reform in three police systems (England and Wales, France, and the Netherlands) from the early 1980s to the present. The decision to begin my analysis in this period is based on the politicization of crime that took place in various Western countries in the late 1970s, which provides an opportunity to examine how political actors have taken up these issues and how such politicization has altered the distribution of power between the levels of government. 9 I will show that the politicization of security issues and new managerialist reforms have reinforced the centralist bias of police organizations, even to the extent of overturning long-standing historical arrangements (as in the Dutch case). 10 The effects are however more complex than unilateral centralization: the balance of power in police systems is also influenced by the weight of tradition, political configurations, institutional ambiguities, and the complexities of police organizations.

These countries were chosen based on the amount of information available,11 my own research, [START_REF]I conducted research in France and England (notably as part of the Refmanpol project[END_REF] and above all, the contrasting ways in which their police systems are organized: while France has a highly centralized "Napoleonic" system combined with a strongly unionized profession, England and Wales, and the Netherlands, have moderately pluralistic systems that combine a small number of regional police forces with national steering bodies. I have chosen to focus my investigation on the trajectories of reform of these three police systems over a period of around forty years, defining such trajectories as "series of reform sequences over the long term, with each one having an impact on its successors and a 'transformative effect' on the system of institutionalized public policies undergoing reform." [START_REF] Bezes | Le concept de trajectoire de réformes: comment retracer le processus de transformation des institutions[END_REF] My analysis will focus in particular on the order of reforming sequences, inherited constraints, the configurations and coalitions of reforming actors, and interdependencies between the different types of reform. 14 The article is divided into two parts. After defining two dimensions of analysis of police systems, I will consider the direction and pace of reform in the three systems. While the changes made appear to be similar (the introduction of coordination systems and new managerialism), a number of different patterns ("Tortoise," "Boomerang," and "Earthquake") emerge. Second, I will look at two dynamics shared by the different countries: new managerialist reforms, and the politicization of security issues. Supported by the dominant values and orientations within the police, new managerialist reforms have had centralizing effects, but these have always been limited by the low transparency and obstructive hierarchy of these organizations. Politicization, meanwhile, pulls in two different directions: the construction of policing and insecurity as political issues has heightened the pursuit of greater control by central governments, but the increased involvement of local authorities and the changing preferences of governments have also resulted in greater fragmentation and the decentralization of police systems.

Trajectories of reform in police systems: Small steps and turning points

I have approached change in police systems by considering the series of reform projects in relation to two dimensions (see Table 1). The vertical dimension explores the effects of the reforms in terms of centralization or decentralization. A country is considered to have a centralized police system when "operational direction can be given routinely to subunits from a single center of control."15 This can be broken down into three registers: regulatory (the legal rules assigning powers to local and central bodies), organizational (the existence of central agencies with a monitoring and supervisory role or, conversely, autonomous local units), and managerial (the use of measuring tools, monitoring performance to increase control or to give subordinate entities more autonomy). The second, horizontal, dimension explores the degree to which systems are integrated and coordinated. It covers local partnership schemes, for example, but also organizational mergers or a shared reporting line to the same government ministry. Different patterns emerge when the trajectories of reform are analyzed in relation to these two dimensions. The "BEST" (Boomerang, Earthquake, Stalactite, and Tortoise) categorization proposed by Christopher Pollitt and Geert Bouckaert helps to reconstruct the scope of the changes in more detail, by analyzing processes (which may be gradual or more sudden) in conjunction with results (which may be incremental or more radical). 16 Unlike many institutionalist studies, which focus on the viscosity of change, this typology does not presume that the decisions of the past (which are only one possible form) have a determining effect, 17 and nor does it limit processes of change to gradual forms, thus remaining open to the possibility of rapid transformations (such as due to a political crisis or in the aftermath of an election). 18 Pollitt and Bouckaert outline four categories: a Boomerang is a situation in which things rapidly return to the old ways of doing things; an Earthquake involves rapid, radical change; a Stalactite is the culmination of gradual but fundamental changes; and a Tortoise is an incremental, limited process of change. As we shall see, the French example demonstrates the incremental Tortoise-like reform of a dualist, centralized model of police organization, while the processes affecting the police system in England and Wales have followed a Boomerang trajectory in which the continuous centralizing reforms of the 1990s and early 2000s were interrupted. In the Netherlands, the introduction of a national police force in the early 2010s can be seen as more of an Earthquake.

Tortoise: Incremental change in France

France has a dualist, centralized police system dominated by two national organizations, one military (the national gendarmerie has around 100,000 officers), and the other civilian (the national police force has around 150,000). 19 Relations within this system have however been partly redefined by the integration of the gendarmerie into the Ministry of the Interior, the creation of local partnerships, the development of municipal police forces, attempts at organizational decentralization, and the introduction of new managerialism.

The integration of the national gendarmerie into the Ministry of the Interior (law of August 3, 2009) has moderated the dualist nature of the French system: whereas gendarmes were traditionally accountable to the Minister of Defense, both gendarmes and police officers are now accountable to the Minister of the Interior. This integration is the culmination of a series of reforms in which the two organizations have "inched closer together," The limited integration of the national police and gendarmerie has been accompanied by reinforced coordination at the local level, in particular through a proliferation of local coordination systems since the early 1980s (from national/municipal police coordination agreements to local security and crime prevention councils, and territorial security and crime prevention strategies and priority security zones). 22 These arrangements have tended to increase the accountability of the police and gendarmerie at the local level (for example by providing local authorities with crime reports and taking part in partnership schemes), without actually resulting in an equal relationship, as they also represent ways for police forces to assert their definitions of security problems locally. 23 This shift is directly linked to the strengthening of the role of local authorities, and more specifically of municipal authorities. The most obvious sign of this has been the increase in the number of municipal police officers over the last thirty years, from 5,600 in 1984 to around 24,000 in 2019. 24 These numbers are however still dwarfed by the total of approximately 250,000 officers in the national gendarmerie and national police, and municipal police officers have limited legal powers compared to their colleagues in the national forces (they only have the status of deputy judicial police officers). Overall, the French public security system cannot be described as having undergone wholescale transformation, since the option to decentralize the public security forces (i.e., by transferring authority over public security officers to territorial authorities) has been consistently rejected by political, administrative, and police elites. There have been a few attempts to municipalize public security forces, such as the bill introduced by two members of the national assembly, Gilles de Robien and André Santini, in September 2000, but these efforts have come to nothing. Similarly, a number of local elected officials who had expressed their support for decentralization backtracked on this once they became ministers: Nicolas Sarkozy, for example, forgot the proposal he had previously made to transfer powers over everyday policing to mayors once he became Minister of the Interior. [START_REF] Sarkozy | Libre[END_REF] Finally, none of the reforms have led to organizational decentralization within the central directorates of the state police forces (the Directorate General of the National Gendarmerie and Directorate General of the National Police). The community policing reform program (1997-2002) had the potential to result in internal decentralization of the way in which the police were organized, if only because it emphasized the generalist role of officers on the ground as being better able to understand crime and security problems in their local area, but ironically, it was implemented in a highly centralized way [START_REF] Roché | Police de proximité[END_REF] and abandoned by the Minister of the Interior in 2002-3underlining the centralist tendencies of the national police. The politicization of crime since the early 2000s and the spread of performance indicators as part of the implementation of the LOLF have also resulted in the central directorates strengthening their grip on local units, with the assignment of numerical targets and routine requests for data leading to a greater dependence on local managers, although gaming practices remain widespread. [START_REF] Douillet | Une centralisation renforcée par le chiffre? Les effets contradictoires des indicateurs chiffrés dans la police nationale en France[END_REF] This performance measurement process is particularly pronounced for middle managers with territorial responsibility (chefs de service), who are regularly assessed against a broad range of indicators (from human resources indicators to crime trends). [START_REF] Lemaire | Les usages de la spécialisation dans la police: les formes discrètes du management public policier[END_REF] While the introduction of priority security zones in 2012 [START_REF] Darley | Le travail policier face aux réformes: une ethnographie de la mise en oeuvre des 'zones de sécurité prioritaires[END_REF] and the everyday security policing doctrine in early 2018 should in principle have been accompanied by giving chefs de service greater responsibility, there are no tangible signs-albeit few evaluations-of internal decentralization within the national gendarmerie and national police.

In France, therefore, most police officers are still employed in the national forces, with attempts at horizontal integration (of the gendarmerie into the Ministry of the Interior).

There has however been an increase in the number of municipal police officers, and a set of legal means (consultation and contractualization) that strengthen the capacity for action of territorial (predominantly municipal) authorities. The changes have therefore swung between the persistent dominance of the centralized police forceswith even a certain organizational centralization within them-and moderate decentralization as an effect of the general shift that began in 1982. 30

Boomerang: The case of England and Wales

In England and Wales, the reforms have been contradictory. During the 1990s and 2000s, the significant role played by the Home Office in policing, the politicization of crime, and the implementation of New Public Management ideas led to increased centralization, before growing criticism of this policy regime led to a partial relocalization of police governance.

The system of governance of the forty-one regional police forces and two London forces (the Metropolitan Police Service and City of London Police) has traditionally been divided into three parts, as enshrined in the 1964 Police Act: local police authorities (replaced by police and crime commissioners or PCCs in 2012, see below), chief constables, and the Home Secretary. With the exception of the Metropolitan Police Service (which reported directly to the Home Office until the early 2000s, see below), the system is anchored in strong local and regional roots. 31 The cumulative effect of the reforms of successive governments since the 1990s has been to increase the influence of the central authorities. First, a legislative change (the 1994 Police and Magistrates' Courts Act) strengthened the power of the Home Office to appoint members of local police authorities. Most importantly, the gradual formation of a centralized performance regime, characterized by centrally-defined numerical targets, transformed the way in which the police were run. The passage of the 2002 Police Reform Act accelerated this trend by creating an annual National Policing Plan accompanied by a set of numerical targets and performance indicators that the police were required to meet. Here we can see a self-reinforcing effect of the reforms, with each government increasing the sophistication of the performance regime created by its predecessors, by adding to it and accentuating the logic of control. The system was finally completed by the creation and strengthening of national agencies responsible for supervising, inspecting, auditing, and even correcting the actions of the police. The role of Her Majesty's Inspectorate of Constabulary (HMIC) was strengthened, but other bodies were also introduced to increase the control exercised by the national authorities, such as the Police Standards Unit, created in 2003 to monitor the performance of the various police services throughout the country. The Serious and Organised Crime Agency (renamed the National Crime Agency in 2013) was established to handle matters of national interest such as organized crime and terrorism, while the Independent Police Complaints Commission (which became the Independent Office for Police Conduct in 2018) was created in 2004 to investigate police misconduct. Since the late 1980s, the Association of Chief Police Officers (ACPO) has gradually taken on a national policy coordination role by formulating standards for regional police forces. 32 Meanwhile, there has been a proliferation of national technology-based initiatives, including a national radio system (Airwave), the Automated Fingerprint Identification System database, and the Automatic Number Plate Recognition (ANPR) system. From 2002 onward, as New Labour invested massively in public services and particularly in the police (the number of sworn police officers reached an all-time high of 144,000 in 2007-8), [START_REF] Loveday | Police Reform in England and Wales: A New Dimension in Accountability and Service Delivery in the 21st Century[END_REF] and recruited around 10,000 police community support officers, [START_REF] Megan | Ripe for the Chop of The Public Face of Policing? PCSOs and Neighbourhood Policing in Austerity[END_REF] the government set binding targets and indicators for regional police forces. This dominance was reflected by the adoption in 2003 of a National Intelligence Model for criminal intelligence, led by ACPO, along with the creation of a National Improvement Police Agency (which became the College of Policing in 2012) to manage training and set professional standards.

In parallel, in 1998 the government created crime and disorder reduction partnerships (CDRPs) followed by community safety partnerships (CSPs), which bring the police together with various local partners to facilitate coordinated action on crime and disorder. [START_REF] Edwards | The Preventive Turn and the Promotion of Safer Communities in England and Wales: Political Inventiveness and Governmental Instabilities[END_REF] Crucially, in the mid-2000s, while those close to Tony Blair continued to support a performance-based mode of government, those in the Home Office were developing ideas and initiatives with a focus on a "new localism." [START_REF] Mclaughlin | The New Policing[END_REF] In 2008, New Labour decided to abandon nationally-set targets, with the exception of a national target that measured public confidence. [START_REF] Newburn | Police and Crime Commissioners: The Americanization of Policing or a Very British Reform?[END_REF] In the early 2010s, several changes were made to police governance to increase the decentralization of the police system. Since 2012, the Police Reform and Social Responsibility Act, which was passed in 2011, has redefined the system of police leadership and supervision, with the election of PCCs for all regional forces replacing local police authorities. [START_REF]In London, the Mayor's Office for Policing and Crime (MOPAC) sets targets as part of a multi-year plan. 39 Newburn[END_REF] PCCs are required to set strategic targets for police services as part of a Police and Crime Plan, to ensure that they are effective and efficient, and to strengthen partnership responses to crime and disorder issues. They are not, however, responsible for the day-to-day management of the police, on the grounds of the principle of operational independence, which is sacrosanct in the police tradition of England and Wales. 39 They are also responsible for appointing chief constables, and for asking them to step down if necessary. Despite a shaky start, with turnout in the 2012 PCC elections ranging from 11 to 22 percent depending on the region, PCCs now exercise a greater leadership role than that operated by the former local police authorities, 40 while the Home Office has stepped back from the role it had played in the operational management of the police over the past fifteen years. 41 Policing in England and Wales is however still mainly funded by national taxation (which accounts for three-quarters of its budget). Similarly, while chief constables are appointed locally by PCCs, access to senior ranks is governed by national schemes and, against a background of budgetary constraints, government departments (more Whitehall-i.e., the government as a whole-rather than the Home Office alone) and agencies (notably HMIC) continue to have a say in setting local priorities by controlling resources. 42 Overall, the pattern of change in England and Wales has followed a Boomerang trajectory (i.e., a rapid return to old ways of doing things 43 ): while new managerialist reforms and the politicization of security issues drove a continuous trend toward both managerial and organizational centralization, this trend ultimately fueled criticism of the excesses of government by indicators and a local democratic deficit, and led to the abandonment of national numerical targets and the election of PCCs in the early 2010s. This rebalancing, involving a return to the moderately decentralized tradition of the British system, took place against a background of budgetary austerity in which the government delegated responsibility while cutting spending.

Earthquake: Radical transformation in the Netherlands

Since 2013, the Netherlands has had a single national police force of around 63,000 officers, led by a commissioner who reports to the Minister of Security and Justice. 44 Such an entity would have been difficult to imagine just a few years earlier: the idea of a decentralized police force with a close relationship with local political authorities was such a strong part of the Dutch police tradition 45 that the idea of a national force seemed simply incompatible with Dutch sensibilities. 46 Until 1993, all towns and cities with a population over 25,000 had their own police force, equating to a total of 147 relatively autonomous police forces, in addition to a 40 The relationship between chief constables and PCCs is still being defined (in relation to the recruitment of deputies and assistants, and resolving conflicts). police organization with military status, the Koninklijke Marechaussee (Royal Netherlands Marechaussee), which was mainly responsible for rural areas. The efficacy of this system was called into question, and in 1993 the Dutch Parliament passed a Police Act reducing the number of forces to twenty-five semi-autonomous regional police forces and one national force (the Korps Landelijke Politiediensten, or National Constabulary). The system was primarily regional (mainly in relation to the distribution of resources) and local (for more operational decisions). It was based above all on a principle of horizontal integration, through continual consultation between mayors, prosecutors, and police chiefs.

The Dutch police then underwent gradual centralization, primarily driven by central priority setting and a performance management system. 47 The autonomy of the national force, which had been created in principle to support the regional police forces, was also increased, to the point of establishing its own investigation unit to replace the inter-regional criminal investigation teams. The lack of any real political or administrative representatives for the police at the regional level also weakened the democratic accountability of this system. Expert reports regularly highlighted insufficient coordination between regional police forces: although they had committed to improving inter-regional cooperation, a 2008 report by the Inspectie OOV (Police Inspectorate) concluded that this was inadequate, and in 2011 the General Audit Office highlighted a failure to provide access to data and insufficient information sharing between forces. The creeping centralization of the Dutch police resulted from the cumulative effects of these composite changes: the collateral effects of reforms instilling New Public Management instruments in the administration, the increased autonomy of the national force, a distance from democratic structures, and growing concern among experts about communication between police forces in a political climate dominated by security concerns. 48 The reforms gathered pace in the early 2010s. Convinced that a national system would be more efficient, the new center-right Minister of Security and Justice (Ivo Opstelten, formerly the mayor of Rotterdam) appointed managers to oversee the transition even before the act was passed, ignoring the opinion of the Council of State and obtaining consent from Parliament in under a year. Once the national force was created in 2013, the key question was how it should work in relation to local actors. The reforms had various potentially contradictory objectives, since they were designed to strengthen and standardize working methods while also preserving the local roots of the police, including by creating "local teams" made up of sixty to two hundred officers who would be responsible for most policing (patrolling, community policing, criminal investigations, and service provision). The extent to which local political actors have been sidelined by the nationalization of the police force varies: while "regional mayors" (typically the mayors of the largest towns and cities, appointed by their peers to act as regional administrators) have undoubtedly lost influence, the country's four hundred or so other mayors have not been wholly marginalized: while the national police sets its own annual priorities, each local authority's Board of the Mayor and Aldermen continues to coproduce the local security strategies developed as part of five-year action plans. The mayors of small towns and rural areas have, however, been more clearly sidelined, especially at a time when reorganizations conducted in the context of austerity are leading to station closures. Overall: Despite all the rhetoric about the local embedding of the police and the need to create local flexibility and more room for "police craftsmanship," the organizational design is [. . .] largely based on a belief in hierarchy, standardization, uniform solutions, and in scaling up and down as ultimate organizational principles. 49 Dutch towns and cities are also employing a growing number of municipal law enforcement officers who have the power to hand out fines and even make arrests, demonstrating their desire to preserve their powers to regulate conduct in urban areas, at a time when the streamlining of the police threatens to distance the police force from local needs. 50

Centralization, the imprint of origins, and contradictory logics

Returning now to the two theories initially identified in the literature-the shared dynamics of centralization and the permanence of specific command structures-it is clear that the centralization argument51 does not apply across the board. It is true for the Netherlands, but applies to England and Wales only for a specific period (1990-2010), and is fundamentally flawed for France, which has seen opposing trends (centralization through government by performance management, and decentralization through the consolidation of municipal police forces). These examples also counter the conventional historical institutionalist explanation proposed by David H. Bayley. 52 In France, the key characteristics of the system (dualism and centralism) have undoubtedly remained prevalent, but the role now played by the territorial authorities, attempts at coordination from above, and the spread of the partnership logic have redefined the components of police configurations. In England and Wales, successive new managerialist reforms and political involvement in policing by consecutive governments centralized the system, before criticism from numerous quarters and the arrival of the Conservative-Liberal Democrat coalition led to a partial relocalization of policing decisions. The case of the Netherlands illustrates a clearer break, after gradual changes: the interplay between the increased autonomy of the national police force and the use of performance indicators favored creeping managerial and organizational centralization, but it was the crisis triggered by IT system failures in the late 1990s that enabled a political entrepreneur to implement centralizing reforms. The police systems in the Netherlands and in England and Wales have been much more permeable to change than their French counterpart: the creation of national police forces represents a powerful institutional lock-in, supported by the coalescence of knowledge and professional interests situated at the heart of the state, the mobilization of professional organizations, and the organizational and political costs associated with such reforms. Finally, the changes are founded on the institutional ambiguity of historical arrangements, with some traditionally secondary components being emphasized, such as territorial authorities in the French Napoleonic system, and national supervisory and steering methods in the pluralistic systems. I will now turn to analyzing these patterns of change by focusing on the spread of the New Public Management approach and the spread of politicization, which have had varying impacts on the three police systems.

Politicization, new managerialist reforms, and the centralization of police systems

New managerialist reforms based on performance indicators and numerical targets have become widespread, and the dynamics of politicization are also seen across Europe, including in the three systems analyzed here. These two drivers of reform may appear to be separate, with new managerialism sometimes appearing to be a form of depoliticizing public policy (as politics gets lost amid the production of targets and indicators). 53 But numerous analyses have demonstrated how the choice of monitoring indicators constructed a specific politics and involved implicit values and norms. Above all, as we shall see, the way in which new managerialist reforms have been implemented is very closely linked to the mobilization of political actors anxious to provide their electorate with evidence of effective policing.

On the one hand, new managerialist reforms have reinforced centralization mechanisms, even if the characteristics of police organizations (multiple levels of hierarchy, autonomy within units and professions, and a relative lack of transparency) have favored reappropriation and gaming practices. On the other hand, the dynamics of politicization have pulled in opposite directions: the national politicization of crime and policing issues has resulted in increased control over police organizations by central governments, but the mobilization of local authorities and a delegation rationale has led to a fragmentation and decentralization of police systems.

Policing and new managerialist reforms: Obstructed centralization

The adoption of new managerialist ideas, norms, and instruments-in particular performance measurement tools-strengthened organizational centralization by assigning numerical targets and facilitating performance monitoring by the central authorities. As we have seen, in England and Wales, the measurement of police performance, coupled with supervisory agencies, was a lever for strengthening the Home Office's control over regional police forces, at least until the early 2010s. Similar trends were also apparent in the Netherlands prior to the government's nationalization of the regional police forces. Management by performance is also present in the centralized French system, leading to a process of internal centralization within the national police force that reduces the autonomy of local units. Centralization through new managerialist tools has not, however, operated in the same way across the three countries: in France, it has strengthened the vertical logic of an already integrated system (dominated by two state forces, the national police and the gendarmerie), while in England and Wales and the Netherlands (until 2013), it has involved a remote form of government in which the executive has increased its capacity to steer and supervise regional police forces.

This finding of increased centralization may seem surprising. While associated with a number of consistent organizational concepts and formats (such as separating strategy from operations, breaking down vertical bureaucracies, and management by results), New Public Management can include varying degrees of centralization. [START_REF] Bezes | Introduction: New Public Management et professions dans l'État: audelà des oppositions, quelles recompositions?[END_REF] The version promoted at the end of the 1990s, particularly in the UK, put more of a focus on the specific features of public services, the quality of the service offered, the partnership approach, local aspects, and involving the public in setting priorities. [START_REF] Bezes | Introduction[END_REF] In policing, however, a mainly centralizing logic was followed, with the reforms generally designed to strengthen control in order to ensure effective policing, particularly in the fight against crime. This mode of governance favors the use of indicators in steering departments and units, performance evaluation, standard procedures, and hierarchical structures that reduce the control of professionals over their own work. [START_REF] Evetts | New Professionalism and New Public Management: Changes and Continuities[END_REF] This vertical, top-down interpretation of New Public Management is supported by ideas that favor a pyramidal bureaucratic logic, a widespread tradition in police organizations, in which the chain of command is central and there is "an insistence on compliance, and punitive supervision based on detailed rules covering almost everything that an officer might do." [START_REF] David | Police for the Future[END_REF] As David Weisburd and his colleagues have analyzed in relation to the take-up of Compstat by American police forces, the spread of performance monitoring and measurement systems can be interpreted as a revival of the bureaucratic "command and control" mold of policing. 58 I will return below to the external political pressures behind this, but at this stage would note that this logic of control forms part of a classic template for police organizations, revived by the tools of New Public Management and by technology. The spread of these performance management tools and techniques represents an attempt at streamlining, in the name of various myths about how to make policing more effective (such as regular monitoring of indicators, setting numerical targets, and integrating communication systems). [START_REF] Bezes | Le nouveau phénomène bureaucratique: le gouvernement par la performance entre bureaucratisation, marché et politique[END_REF] These reforms have not, however, always had the same automatic effects, as police forces are capable of inflection and reappropriation. Where centralization has taken place, it has been obstructed by three things: internal tensions within police organizations, the gaming of targets, and conflict with demands from outside the police. First, these reforms have further increased the pressure on police organizations, which are pulled in two different directions, from above and below, by managers and their subordinates, with the latter criticizing the former for their excessive focus on numbers at the expense of real police work and complaining about the incessant data required by this type of governance. [START_REF] England | Policing, New Public Management and Legitimacy in Britain[END_REF] Second, their implementation has been followed by a series of deceptive practices, of which gaming has been widely documented in the literature. 61 Faced with centralized demands to produce "results" (reduce crime and increase the clearance rate), police forces tinker, circumvent, and misappropriate: they under-record certain crimes by redirecting complainants, rejecting certain offenses, and recoding others, in order to meet the targets imposed on them. Finally, this logic of internal centralization based on monitoring indicators has come into conflict with demands for accountability from outside the police, for example by integrating responses to security problems with people's quality of life. The contradictions highlighted by the Audit Commission in England and Wales in the early 2000s between local partnerships and the strict regime set out by national indicators applies to the various national configurations more broadly: Inevitably, there is a tension between the national performance indicators relating to crime reduction and the broader delivery of community safety.

Partnerships that focus too narrowly on national issues alone will fail to attend to local priorities and will not serve local people well. [START_REF]Community Safety Partnerships[END_REF] In other words, overall, the spread of new managerialism has contributed to the centralization of police systems, while increasing both internal tensions (between hierarchical levels, and between central directorates and local units) and external tensions (between the police and their local partners).

More broadly, this highlights the gap between political discourse, the handling of reforms, and the effects of reforming initiatives. Announcements of organizational decentralization should not be taken at face value, as demonstrated by the community policing reform program in France between 1997 and 2002: the reform was supposed to give officers more freedom and better integrate the police into communities, but it was conducted in a highly centralized manner. Similarly, it was claimed that the centralization of policing in England and Wales in the 1990s, and in the Netherlands in the 2010s, would lead to better quality police services more suited to local needs, but this has not been borne out by subsequent evaluations. This issue merits further investigation, and connects with traditional research on police organizations: rhetoric appears to take precedence over reality, [START_REF]Community Policing: Rhetoric or Reality[END_REF] with decentralizing reforms and/or reforms designed to improve the quality of the service for the local community often announced but seldom effectively implemented. This stems from the potential gap between political discourse (aimed at a general audience) and the power relations internal to public decision-making-raising the broader question of intervention by political actors in policing policy.

Politicization and police reform: Is centralization inevitable?

The term "politicization" is used here to describe the way in which political actors take up security, and more specifically policing, issues in conjunction with various types of interlinked actors and spaces (the media, expert forums, governmental and parliamentary forums), within a framework dominated by democratic political competition (competition between parties, and elections). [START_REF]Studying politicization thus involves examining contact points, arenas of decision-making and debate forums, but also the interactions (expansion of alliance networks and exchanges) between these different actors" (Déloye and Haegel[END_REF] This latter dimension is crucial: in all three regions, policing has become a salient political issue that is debated and highlighted by actors (party, parliamentary, and governmental actors) in the political sphere. Three forms of politicization can be distinguished, each with different effects on the centralization of police systems. The first, which has operated in all three countries, stems from the political sensitivity of security issues at the national level, resulting in political involvement that is driven by a combination of an electoral rationale, the media cycle, and government decisions. This form of politicization has typically resulted in greater centralization, but the picture is a nuanced one, as central governments do not by any means control the entire process. We therefore need to consider two other forms of politicization: action by local authorities in the context of security-related demands from the electorate, and the delegation of responsibilities to local actors by central elites reviving the localist imaginary.

The first form of politicization-an increased demand for results on the part of the government, in search of evidence to show the electorate regarding the fight against crime-has been prevalent in all three systems, at different periods (France in the 2000s, England and Wales in the 1990s, and the Netherlands at the turn of the 2010s), resulting in combative, even warlike political rhetoric (declaring war on crime), focusing policing priorities on the fight against crime, demands for regular data, and even symbolic actions to mark political control over these issues, and thus strengthen the executive logic with its expectation of immediate results. [START_REF]As there is insufficient space here to embark on a discussion of the effects of terrorism on state policies, I refer the reader instead to the summary by Frédéric Ocqueteau[END_REF] In France, Sarkozy's time at the Ministry of the Interior (2002-5 and 2006-7) offers a striking illustration of this: statistics were used as a way of demanding a reduction in crime figures from the police, with the imperatives of ministerial communication ultimately taking precedence over police work. [START_REF] Mucchielli | Le 'nouveau management de la sécurité' à l'épreuve': délinquance et activité policière sous le ministère Sarkozy (2002-2007[END_REF] A very similar logic was deployed by New Labour under Tony Blair between 1997 and 2007 in relation to street crime. [START_REF] Reiner | The Politics of the Police[END_REF] Criminologist Michael Tonry, then director of the Institute of Criminology in Cambridge, has identified thirteen "crime summits" (ranging from international organized crime to "gangsta rap") and some thirty government initiatives (from a system of protection for burglary victims to a crackdown on sex tourism, and successive proposals to combat antisocial behavior), taking place over the period from November 1999 to January 2003. [START_REF] Tonry | Punishment and Politics[END_REF] In 2002, Blair held a series of street crime summits, increasing pressure on regional chief constables to be accountable on a regular basis and thus directly reinforcing central government control.

In the Netherlands, the politicization of security issues went hand in hand with an increased desire for central control. While the push for decentralization was traditionally driven by the idea of the need for checks and balances, this was replaced in the early 2010s by the efficiency gains and greater organizational control that it would supposedly enable. A turning point came in 2010, when the communication problems between regional forces became a public issue: the IT system BVH (Basis Voorziening Handhaving), introduced in 2009 to facilitate communication between the country's twenty-five police forces, malfunctioned, with major disruption of information sharing. This crisis was characterized by highly negative media coverage and outrage from police unions, making the lack of a true national police system into a public issue. While this new logic of problem definition gained importance, it was politics that played a crucial role, with the new Minister of Security acting as a political entrepreneur to push through this reform, which was adopted in less than a year. He was supported in this by the police unions and the prosecutor's office, while mayors, who were opposed to the reform, saw their influence decline. 69 The dominant political coalition thus problematized the policing issue as resulting from a lack of efficiency due to the excessive fragmentation of regional police forces. Centralization was thus presented as the solution to complexity and insufficient efficiency in the fight against crime.

These affinities between politicization, centralization, and a repressive approach to policing are unsurprising, since the mobilization of punitive rhetoric and repressive instruments is central to the affirmation of the regalian authority of state power.70 This is captured by the concept of "punitive populism" in the field of criminal justice, which describes how governments have strengthened their repressive arsenal and employed aggressive rhetoric in a strategy primarily guided by the pursuit of votes. This consists of attracting the attention of the national media through political announcements that structure the agenda, striking slogans, and carefully orchestrated public appearances. 71 This politicization, which is entwined with the priorities of the media, can be interpreted through the lens of Hugh Heclo's idea of "permanent campaigning," which describes how the line between governing and campaigning is becoming blurred and government activities are being used to increase the popularity of politicians. 72 This naturally results in centralization, via demands for figures to be included in regular communications reporting on the success of initiatives, and immediate political reactions to events attracting media attention.

The other two forms of politicization have opposing effects on the dynamics of police systems, by reinforcing the logics of decentralization. In France, the development of municipal police forces is the most obvious manifestation of a transformation that has now been extensively analyzed: since decentralization, mayors have been made responsible by their fellow citizens for "everyday quality of life" issues, leading many of them to focus on security issues. It is thus an example of politicization from "below," originating in the mobilizations of the municipal authorities, leading some mayors to revive the Third Republic image of mayors as the "patron of local security." 73 Over the past forty years, French cities have focused services on prevention and public security issues, and developed municipal police services (see above). Local politics have had a considerable influence on this: both inter-party competition for mayorships, and intraparty competition to exercise municipal power have been major determinants of the institutionalization of security in municipal services and the development of municipal police forces. [START_REF] Freyermuth | L'offre municipale de sécurité: un effet émergent des luttes électorales. Une comparaison des configurations lyonnaise, niçoise, rennaise et strasbourgeoise (1983-2001[END_REF] Here, politicization has had the opposite, or at least complementary, effect to the one discussed above: it has contributed to local authorities taking action, driving them to acquire their own resources, and even to criticizing the interventions of national police forces as being insufficiently in tune with the needs of the public. These local actions have thus moderated centralization mechanisms, albeit with major variation between regions: to take only the number of municipal police officers in the cities with the largest forces, staffing ratios range from 2.58 municipal police officers per 1,000 inhabitants in Cannes, to 0.37 in Nantes. 75 In France, local politicization of security issues combined with the effects of decentralization thus counterbalances the traditionally centralized distribution of personnel and the way in which forces are organized. Importantly, this is merely an inflection rather than a major transformation of the system, as mayors are reluctant to risk taking on full responsibility for crime-related issues (see above).

The third and final form of politicization is derived from the two discussed above: like the first, it stems from the inclusion of police and security issues in the national political sphere (by government actors, parties, and public policy forums) but like the second, it is reflected in the relative decentralization of police systems. The case of England and Wales in the early 2010s offers a striking illustration of this: there was indeed politicization at the national level, insofar as the mode of governing policing (and the extent to which it should be localized) was discussed in expert, party, and governmental forums, but this was reflected in a delegation of responsibilities in line with a localist imaginary combining local accountability with democratization of policing.

Over the course of the 2000s, expert and professional elites, and then political elites, began to criticize a style of government based too strictly on the achievement of numerical targets, resulting in standardization ("one size fits all"); 76 and they also promoted the need for the police to have stronger local roots. 77 To use Eugene McLaughlin's phrase, a "'now you control the cops' spin" was evident in both main parties. 78 New Labour initiated an internal discussion about new forms of local accountability, 79 while the Conservative party began to redefine its program in the 2000s, fueled by the work of the think tank Policy Exchange and combining an eclectic range of influences, from New York's "zero tolerance" approach to increased transparency and greater local democratic control. This latter idea gradually led to the party proposing an elected commissioner, 80 foreshadowing the future PCCs, with a view to "[reducing] interference in local policing from Whitehall." 81 In the end, the Conservative-Liberal Democrat coalition made the change seem like a break with the past, with the creation in 2012 of directly elected PCCs designed to embody leadership and democratic control over regional police forces. Avoiding blame is, however, one of the main elements in political communication, and the new coalition government accompanied this reform with a massive plan to reduce central government funding of regional police forces (with a 25 percent cut in funding from 2011 to 2015). Transferring the leadership of the police to the PCCs thus shifted political responsibility at a time of delivering bad news. The central government thus decentralized, while requiring local authorities (in this case the PCCs) to handle the political fallout of budget cuts.

Ultimately, studying these types of politicization highlights the relative uniqueness of national configurations. In the Netherlands, the national politicization of these issues resulted in the creation of a national police force at a time when efficiency was a key concern and traditionally pro-decentralization actors were weakened. In France, politicization within a centralized system has reinforced the characteristics of this system (information flow and targets set from Paris), but has been counterbalanced by forms of local politicization that have led to increased pluralization. In England and Wales, control over police forces increased from the early 1980s in the name of supposed efficiency gains, before recognition of the adverse effects of these dynamics, combined with a revival of localism among political actors, favored the partial relocalization of policing policy in the early 2010s.

Conclusion

From moderation of the centralized, dualist character of the French police system to a Boomerang phenomenon in the police organization of England and Wales, where the process of centralization was interrupted in the early 2010s, and the drastic centralization of the Dutch police system in the early 2010s after years of incremental change, the various reforms described in this article do not fit with the two dominant theories in the literature on police system reform-centralization and preservation of the historical characteristics of the systems-discussed in the introduction. These national configurations have in fact all been permeated by contradictory logics of two different kinds, as this analysis of the forms of politicization and spread of new managerialist norms has attempted to identify. First, they have swung between internal and external modes of evaluation, between strictly quantitative criteria and more qualitative modes of evaluation. While new managerialist principles have encouraged the production of indicators (to measure the activity of police organizations) and the strengthening of organizational control, government through cooperation has encouraged shared local targets to be set jointly. These systematized performance measurement and reporting measures have formed new systems of constraints or "iron cages," 82 while the negotiating bodies represent new "glass cages." [START_REF] Lascoumes | [END_REF] Second, the national politicization of security issues has driven political actors to seek greater control over police services, in a logic of permanent campaigning, while other forms of politicization (the mobilization of local authorities, and delegation by central elites) have conversely increased the polycentric nature of the systems. These national configurations partially incorporate historical legacies (dualist centralism and moderate pluralism) in their contemporary reforms (the fragmentation of political authority, spread of new managerialist norms, pluralization of police services, and politicization of security issues).

Rather than simply concluding that police systems are cloaked in a logic of centralization, it would seem more accurate to describe police forces as having centralist tendencies. Budgetary constraints, the spread of new managerialist norms, and the national politicization of security issues have revived the classic vertical template of police administrations. Notably, it is clear that reforms supposed to improve the quality of local policing (such as the initiatives in England and Wales in the late 1990s, and the 2013 reform in the Netherlands), or the greater decentralization of responsibilities (such as the community policing reform program in France) can result in highly vertical modes of action. These apparently paradoxical findings are the result of the types of actors involved. Professions, interest groups, specialist directorates, and senior officials are important actors in any reform process, while citizens, although targets of the discourse (as part of the general audience), are merely secondary protagonists in decision-making spheres. Centralization of police systems is not inevitable, but in the absence of a counterbalance, organizational and professional biases may lead to it by stealth.

One final question, only briefly touched on in this article, is the relationship between the level of government and style of policing: does the fact that the police are local (or national) make a difference to the favored approach (whether it is more or less aggressive, or oriented toward crime control)? Some studies have found that the pluralization of police services, with the proliferation of local police officers with various statuses (police community support officers in England and Wales, municipal law enforcement officers in the Netherlands, and the municipal police in France) has involved the spread of practices and representations of police action more aligned to a "soft" form of policing (a police that listens to the public, focuses on communication, and responds to the demands of the population rather than favoring projection, control, and the use of force). 84 In France, the hope that municipal police forces will be the real "community" police force is often expressed. There are however signs of the opposite logic, as local officers seek to resemble the more prestigious traditional state police forces, which have more legal powers and are supposedly more professionalized. The mechanisms of isomorphism, stoked by unions advocating greater protection, as well as the authority to carry arms and to have the powers of the "real" police, risk leading to alignment, rather than to the greater divergence that a pluralistic police system should make possible.

77

  See the report from the head of HMIC: Ronnie Flanagan, "The Review of Policing," The Home Office, 2008. 78 McLaughlin, The New Policing, 190. 79 Newburn, "Police and Crime Commissioners," 35-36. 80 Newburn, "Police and Crime Commissioners," 31-38. 81 Damian Green, Minister of State for Policing 2012-14, speech, Policy Exchange, February 23, 2012. See Patrick Hassenteufel and Jacques de Maillard, "Le recours au marché comme processus politique: les réformes du gouvernement de coalition britannique (2010-2015) dans la santé et la police," Gouvernement et action publique 6, no. 4 (2017): 101-26 (113-6).

Table 1 .

 1 The dimensions of comparison of police systems

	Dimension	Variables
	Vertical	-Regulatory (binding legal rules versus
	(centralization/decentralization)	autonomy of local units)
		-Organizational (establishment of national
		bodies with a supervisory role versus the
		development of autonomous units)
		-Managerial (development of managerial
		tools for measuring and monitoring
		activity versus managerial autonomy)
	Horizontal	-Existence or absence of coordination
	(integration/fragmentation)	(coordination systems at the national
		and/or local levels versus absence of
		regulation)
		-Merger or fragmentation (merger of
		separate entities versus fragmentation of
		unified entities)

  41 Adam Crawford, "The English and Welsh Experiment in Democratic Governance of Policing Through Police and Crime Commissioners: A Misconceived Venture or a Good Idea, Badly Implemented?" in Comparing the Democratic Governance of Police Intelligence: New Models of Participation and Expertise in the United States and Europe, eds. Thierry Delpeuch and Jacqueline Ross (Cheltenham: Edward Elgar, 2016), 116-52. 42 Trevor Jones and Stuart Lister, "Localism and Police Governance in England & Wales: Exploring Continuity and Change," European Journal of Criminology 16, no. 5 (2019), 552-72.

43 Pollitt and Bouckaert, Continuity and Change, 19. 44 Jan Terpstra and Nicholas Fyfe, "Policy Processes and Police Reform: Examining Similarities and Differences between Scotland and the Netherlands," International Journal of Law, Crime and Justice 42, no. 4 (2014), 366-83. 45 Jan Terpstra, "Towards a National Police in the Netherlands: Background of a Radical Police Reform," in Fyfe, Terpstra, and Tops (eds.), Centralizing Forces, 137-55 (137). 46 Dorian Schaap, The Police, the Public and the Pursuit of Trust: A Cross-National, Dynamic Study of Trust in the Police and Police Trust-Building Strategies (The Hague: Eleven International Publishing, 2018).

Table 2 .

 2 Changes in police systems Jan Terpstra, "Local Policing in a Nationalized Police Force: A Study on the Local Teams of the Netherlands' National Police," Policing 15, no. 1 (2018): 251-62 (11 of PDF). 50 Ronald van Steden, "Municipal Law Enforcement Officers: Towards a New System of Local Policing in the Netherlands?," Policing and Society 27, no. 1 (2017), 40-53.

		France		England	and	Netherlands
					Wales
	Centralization	-Development of	-	New	-Creation of regional police
	/decentralizati	municipal police	managerialist	forces (1993)
	on	forces (1983-)	transformations	-Centralization (national
		-Failure of the	(1990-2009), then	objectives and performance
		community		easing off (2010)	measurement)
		policing	reform	-Creation of	-Creation of a national police
		program	(1997-	autonomous	force (2013-)
		2002)		national agencies	-Development of municipal
		-	Centralization	with regulatory	law enforcement officers
		driven	by	role
		performance	-Election of
		indicators (2002-	police and crime
		12)			commissioners
					(2011-)

49

This work is intended to provide an up-to-date review based on secondary sources in the three regions. It is based on a systematic literature search for work in French and English on institutional transformations. This

Bayley, Patterns of Policing, 54.

Christopher Pollitt and Geert Bouckaert, Continuity and Change in Public Policy and Management (Cheltenham: Edward Elgar, 2009),

17-20.

Frédéric Ocqueteau, "Fusionner police et gendarmerie nationales? Sur l'histoire d'un essai non transformé," Études et données pénales (Paris: CESDIP, 2017), 28.

See François Dieu, "Gendarmerie et dualisme policier," Res Militaris, special issue, 2019, available online at: https://resmilitaris.net/wpcontent/uploads/2021/09/res_militaris_article__dieu_gendarmerie_et_dualisme_policier.pdf.

22 Sébastian Roché, "Vers la démonopolisation des fonctions régaliennes: contractualisation, territorialisation et européanisation de la sécurité intérieure," Revue française de science politique 54, no. 1 (February 2004): 43-70; Tanguy Le Goff, Les maires. Nouveaux patrons de la sécurité? (Rennes: Presses universitaires de Rennes,

2008).23 Séverine Germain, "Les cadres policiers face à la territorialisation de l'action publique: une institution à la conquête du local," Sciences de la société 90 (2013

): 42-57.24 Cour des Comptes, "Les polices municipales," special public report, 2020, 29.

For a summary, see Clive Emsley, "The Birth and Development of the Police," in Handbook of Policing, ed. Tim Newburn (Cullompton: Willan, 2008), 72-88.

Terpstra, "Towards a National Police in the Netherlands," 141.

René Van Swaaningen, "Public Safety and the Management of Fear," Theoretical Criminology 9, no. 3 (2005): 289-305.

Terpstra and Fyfe, "Introduction: A 'Transformative Moment in Policing'."

Cécile Vigour, "Justice: l'introduction d'une rationalité managériale comme euphémisation du politique," Droit et société 63-64, nos. 2-3 (2006): 425-55.

In the Netherlands, mayors are appointed by the government (from a list drawn up by the city council).

Garland, Culture of Control.

See, for example, the discussion in Megan O'Neill, Police Community Support Officers: Cultures and Identities within Pluralised Policing (Oxford: Oxford University Press, 2019), 136-48.

This was the approach taken by New Labour more generally, with the role of spin doctors in particular (Alastair Campbell and Peter Mandelson) extensively analyzed elsewhere (Peter Oborne, Alastair Campbell, New Labour and the Rise of the Media Class [London: Aurum Press, 1999]). On crime specifically, see the analysis by Eugene McLaughlin, "'Same Bed, Different Dreams': Postmodern Reflections on Crime Prevention and Community Safety," in Crime Control and Community: The New Politics of Public Safety, eds. Gordon Hughes and Adam Edwards (Cullompton: Willan, 2002), 46-62. 72 Hugh Heclo, "Campaigning and Governing: A Conspectus," in The Permanent Campaign and Its Future, eds. Norman J. Ornstein and Thomas E. Mann (Washington, DC: American Enterprise Institute/Brookings Institute, 2000), 1-37.


Daniel Cordier

Gérard Liger-Belair

David Bonhommeau

Thomas Séon

Nathalie Carrasco

Capillarity processes at Titan and beyond

la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Capillarity processes at Titan and beyond

The manifestations of capillarity are countless in daily life, going from liquids ascension in fibers to the dynamics of bubbles and droplets. On a scientific point of view, hydrodynamics of capillarity is a rather old field, but it is still the subject of very active researches (de Gennes et al. 2004;Drelich et al. 2020) with a wide variety of applications like micro-lenses or blood circulation. The two last decades of space exploration have revealed the existence of several extraterrestrial liquid phases: liquid methane-ethane-nitrogen mixtures in Titan's polar regions (Stofan et al. 2007), liquid water on Enceladus (Porco et al. 2006) and probably on Europa (Sparks et al. 2017), while many evidences speak in favor of the massive presence of liquid water at the surface of Mars, billions years ago (Nazari-Sharabian et al. 2020). In addition, the presence of a global, subsurface water ocean, is suspected in other major icy bodies: Ceres, Callisto, Ganymede, Pluto, etc. Important planetary processes are driven by capillarity: the floatability of small objects, the formation and size distribution of raindrops or the aerosol formation by bubbles burst at ocean surface. From one planetary context to another, the nature of the working liquid and the gravity changing together, the effect of capillarity may be significantly altered. However the impact of this process on the observations of extraterrestrial liquid phases has been few addressed yet.

In this work, we address largely the impact of capillarity in the frame of planetary exploration, with a particular focus on what could be observed by Dragonfly, the future Titan's in situ mission. We question the flotation of small solid particles at the surface of a liquid. We also investigate some properties of extraterrestrial rain droplets and their possible ground imprints. We discuss the interaction of floating films with bubbles bursting, and we close our purpose by considering raindrops absorption into a porous soil. All physical processes are questioned in the perspective of their potential geophysical implications.

An example of process: the floatability by capillarity

The presence of some floating material, over an interface between a liquid phase and a gaseous phase, can yield to major consequences by affecting exchanges of energy, momentum and matter between the phases. The form of this floating material may vary from a tiny monomolecular microlayer to a thick layer similar to sea ice. At the surface of terrestrial oceans, the presence of a thin floating film, produced by biological activity (Lin et al. 2003), has a damping effect on wave activity; marine films is an important topic, and constitutes a full-fledged academic discipline (Gade et al. 2006). Broadly speaking, a solid material is able to float at a liquid surface with the help a two physical processes: (1) the well known Archimede's buyoancy force, for materials less dense than the liquid, (2) capillary forces. This is the second effect we study here ! ! "

Discussion

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Fig. 1 :

 1 Fig.1: Sketch of a spherical solid particle, of radius R and density ρ , floating at the surface of a liquid with the density ρ . The meniscus (blue line) is represented by the equation z = f (x), the surface tension of the interface is σ, while the contact angle between the solid and the liquid is denoted θ ; θ is the filling angle. The difference of height between the plan of flotation and the surface of the unperturbated liquid is h . The local tangent to the meniscus has the angle ψ with the horizontal. The gravity is represented by g.