La mission JUICE de l’ESA sera la troisième mission d’exploration entièrement dédiée au système de Jupiter, et la première à se concentrer sur les lunes Galiléennes glacées susceptibles d’abriter des océans d’eau liquide. Prévue pour un lancement en 2022 et une insertion en orbite jovienne fin 2029, la sonde emportera parmi ses 11 instruments le spectro-imageur MAJIS. Les données d’un tel instrument comprennent une image à haute résolution spatiale de la zone étudiée et un spectre pour chacun des pixels de cette image. Ce spectre, dans la gamme allant de 0.5 à 5.5 µm, permet d’obtenir des informations physico-chimiques sur le contenu du pixel concerné. Le laboratoire où j’ai effectué mon travail de thèse, l’IAS, s’est vu confier la responsabilité de la réalisation de MAJIS. Dans ce contexte, l’objectif de mon travail était de contribuer à la définition et à l’implémentation de l’étalonnage de l’instrument : j’ai pour cela dû comprendre d’abord ses objectifs scientifiques et les exigences instrumentales qui en découlent, et maîtriser les caractéristiques des sous-systèmes qui composent MAJIS. J’ai tout d’abord traité les données de l’imageur intégral de champ de SPHERE, un instrument du VLT, qui avait observé la lune Galiléenne volcanique Io en 2014. Bien que ce satellite soit un objectif mineur de la mission JUICE, j’ai dû me confronter au fonctionnement de l’instrument pour en réduire les données et le traitement des spectres a requis le développement d’un modèle photométrique d’observation de la surface que j’ai pu confronter à la réalité et à d’autres études. L’identification de nombreux biais systématiques dans ces données et la quantification de ses limites de détection spatiales et spectrales m’ont permis de souligner l’aspect critique de la phase d’étalonnage de MAJIS pour que ses données soient exploitables. Avant cette étape toutefois, la connaissance des sous-systèmes qui vont constituer l’instrument est elle aussi nécessaire car certains de leurs paramètres conditionneront le déroulement de cet étalonnage et ils ne pourront pas tous être mesurés à cette occasion. J’ai donc caractérisé, à l’aide des bancs optiques dédiés à l’IAS, le plan focal de l’instrument et surtout son détecteur CMOS infrarouge de type HgCdTe. J’ai pu mesurer ses caractéristiques les plus courantes, comme son courant d’obscurité, sa profondeur de puits, son efficacité quantique, son éventuelle persistance, son bruit de lecture et la linéarité de sa réponse. Dans le cas d’une mission vers Jupiter, un autre aspect des performances du détecteur doit être étudié en détail : sa résistance aux radiations, particulièrement intenses dans la magnétosphère jovienne. J’ai pu effectuer une série de tests sur des détecteurs témoins avec des sources d’électrons, de protons et de photons de hautes énergies, qui m’ont permis de montrer la très bonne résistance du plan focal aux dégâts permanents. Ces données ont aussi permis de caractériser expérimentalement le signal transient induit par un bombardement aux électrons, ce qui m’a permis de valider l’approche de filtrage de ce signal qui sera implémentée en vol. C’est enfin grâce aux résultats de ces trois approches et au développement d’un modèle photométrique complet de l’instrument et de son dispositif d’étalonnage, que j’ai pu discuter l’architecture de ce dernier et proposer des séquences de mesure pour la campagne d’étalonnage. J’ai donc travaillé avec les ingénieurs du laboratoire et des industriels pour réaliser ce dispositif d’étalonnage, sélectionner les sources de lumière qui permettront la mesure de la réponse spatiale, spectrale et radiométrique de l’instrument nécessaires à l’interprétation de ses données au cours de la mission. Au moment de la rédaction de ce manuscrit, le banc d’étalonnage était en cours d’assemblage et j’ai donc pu conclure ce travail par la confrontation de mon modèle aux résultats expérimentaux de validation de certaines voies optiques du dispositif d’étalonnage. / The ESA JUICE mission will only be the third mission fully dedicated to exploring the Jupiter system, and the first with a specific focus on the icy Galilean moons that may harbor oceans of liquid water. Planned for launch in 2022 for a Jovian orbit insertion in late 2029, the probe will carry MAJIS among its 11 instruments, an imaging spectrometer operating from the visible to medium infrared wavelengths. This type of instrument provides very comprehensive data of the observed surface or atmosphere/exosphere: its high spatial resolution capability provides geomorphological information, such as the presence of craters or faults that mark the age and activity of the terrain, while for each pixel a spectrum is acquired. This spectrum, ranging from 0.5 to 5.5 $mu$m, yields physical and chemical information on the region of interest, thus placed in its geomorphic context. The Institut d'Astrophysique Spatiale, my PhD host laboratory, has a legacy of development of such instruments, prominently OMEGA aboard the 2003 Mars Express probe, of which MAJIS is the latest and current project. In this context, my work’s aim was to contribute to the definition and implementation of the instrument’s calibration: to achieve that I first had to understand its scientific objectives and the resulting instrumental requirements, as well as mastering the characteristics of MAJIS subsystems. As part of that process, I analyzed recent data of Io acquired with SPHERE, an integral field spectrometer on the VLT, which possesses similarities with the expected data products of MAJIS. Though this satellite is a minor objective of the JUICE mission, I had to understand the instrument itself in order to reduce its data and the spectra analysis required the development of a photometric model of a surface observation which I confronted to the reality and to previous studies. The identification of many systematic biases in these data and the quantification of its spatial and spectral detection limits allowed me to highlight the critical aspect in the upcoming calibration phase of MAJIS in order to get interpretable in-flight data. To reach this goal the knowledge of the subsystems of the instrument is also necessary because their behavior will condition the calibration scenario and all their parameters will not be measured again on this occasion. I have therefore characterized, using dedicated optical benches, the focal plane of the instrument and especially its HgCdTe CMOS infrared detector. I was able to measure its most common characteristics, such as its dark current, full-well capacity, quantum efficiency, persistence and readout noise. The knowledge of QE and full-well depth was incorporated into an end-to-end radiometric model of MAJIS, which I fed with the spectral radiance of different scientific targets, including modeled ionian surface flows. In turn, this allowed me to select sources and optical solutions suitable for calibration. Due to the intense radiation levels in the Jovian magnetosphere, the detector’s resilience to radiations also needed to be studied. I was able to perform three test campaigns on control detectors with sources of electrons, protons and high energy photons, which allowed me to show the overall very good resilience of the focal plane to permanent damages and to validate the foreseen transient effects reduction algorithms. These three approaches required that I develop a complete photometric model of the instrument and of its calibration setup which I used to discuss its design and submit test sequences for the calibration campaign. I have worked with our laboratory engineers and industrials to design then build the calibration setup with the light sources that will allow measurement of the spatial, spectral and radiometric responses of the instrument, required to interpret its data during the mission.

No description available.

<div>Planetary rings are, and have been, a common feature throughout the solar system.</div><div>Rings have been observed orbiting each of the giant planets, several Trans-Neptunian Objects, and debris rings are thought to have orbited both Earth and Mars.</div><div>The bright, massive planetary rings orbiting Saturn have been observed for centuries, and the Cassini Mission has given researchers a recent and extensive closeup view of these rings.</div><div>The Saturn ring system has served as a natural laboratory for scientists to understand the dynamics of planetary ring systems, as well as their influence on satellites orbiting nearby.</div><div>Researchers have shown that planetary ring systems and nearby satellites can be tightly-coupled systems.</div><div><br></div><div>In this work, I discuss the physics which dominate the dynamical evolution of planetary ring systems, as well as the interactions with any nearby satellites.</div><div>Many of these dynamics have been incorporated into a one-dimensional mixed Eulerian-Lagrangian numerical model that I call "RING-MOONS," to simulate the long-term evolution of tightly coupled satellite-ring systems.</div><div>In developing RING-MOONS, I have discovered that there are three evolution regimes for tightly-coupled satellite-ring systems which I designate as the "Boomerang," "Torque-Dependent," and "Slingshot" regimes.</div><div>Each regime may be defined using the rotation period of the primary body and the bulk density of the ring material.</div><div><br></div><div>The slow rotation period of Mars places it in the Boomerang regime.</div><div>I hypothesize that a giant impact with Mars ejected material into orbit, forming a debris ring around the planet.</div><div>Using RING-MOONS, I demonstrate how Lindblad torques cause satellites which form at the edge of the ring to initially migrate away from the ring, but over time as the mass of the ring decreases, tidal torques always cause the satellites to migrate inwards.</div><div>Assuming the satellites rapidly tidally disrupt upon migrating to the rigid Roche limit, a new ring is formed.</div><div>I show that debris material cycles between orbiting Mars as a planetary ring, or as discrete satellites, and that Phobos may be a product of a repeated satellite-ring cycle.</div><div>Uranus, which has a faster rotation rate falls within the Torque-Dependent regime.</div><div>Hypothesizing that a massive ring once orbited Uranus, I use RING-MOONS to demonstrate how the satellite Miranda may have formed from such a ring, and migrated outwards to its current orbit, but that any other satellites would have migrated inwards overtime.</div><div><br></div><div>Lastly, I examine Trans-Neptunian Objects (TNOs) in binary systems.</div><div>Tidal torques exerted on each body can decrease the mutual semi-major axis of the system.</div><div>I outline the conditions for which a fully synchronous system may experience a complete decay of the mutual orbit due to tidal torques.</div><div>As the semi-major axis decreases, it is possible for the smaller of the two bodies to shed mass before coming into contact with the more massive to form a contact binary.</div><div>I hypothesize that Chariklo and Chiron are contact binaries that formed via the tidal collapse of a binary TNOs system, and demonstrate how mass shedding may have occurred to form the rings observed today.</div>

The search for extra-terrestrial life is guided by the classification of promising candidate worlds. In this classification the habitable zone acts as a measure for the perceived habitability of a circumstellar body. Habitable zone definitions vary between using a conservative and an optimistic limit. As the Sun progresses through stages of stellar evolution previously uninhabitable outer moons may receive sufficient heating for the existence of liquid water on their surface. To evaluate the possibility for life on these moons the time inside the habitable zone is calculated and compared to estimates for the time for life to develop on Earth. For these calculations the stellar evolution models of PARSEC and Dartmouth are employed. A class of moons is discovered whose time inside the habitable zone is longest during the horizontal branch evolutionary phase (fueled by helium burning in the core). Since the horizontal branch luminosity is near constant, this class is of particular interest due to being less dependent on a stabilizing climate mechanism to regulate atmospheric composition needed to counteract luminosity changes. Ultimately, it is found that regardless of moon, stellar evolution model, and habitable zone definition no post-main sequence time inside the habitable zone is as long as the time for life to arise on Earth. / <p>Research presentation</p>

The evolving science of astrobiology for the search for life beyond Earth has put focus on the possibility of subsurface bodies of liquid water beneath the surface of icy moons within our Solar System. Specifically, the Jovian moon of Europa and the Saturnian moon of Enceladus show telling characteristics of endogenous heating through their complex tidal resonances with their parent planets – suggesting the presence of oceans of liquid water and therefore a potential for astrobiology. Today, the planning of upcoming satellite missions to guarantee the identification of completely unknown, possibly habitable environments has become an intriguing task for space agencies worldwide. A method of guidance, ground-truthing, debugging and testing of the viability of planned satellite missions is to utilize relatively accessible analogue environments on the Earth. Fortunately, the research of Antarctic subglacial water environments has been acknowledged as the most suitable analogues to the environments of Europa and Enceladus. Given its recorded motions of ice dynamics, erosion, complex thermal systems, and occasions of sampled microbes within – these sensitive, exotic environments beneath the Antarctic ice bed are currently assessed for their suitability as habitats for extremophilic microorganisms, which may provide important insights into the potential existence of habitats, perhaps even life, on icy moons. Ultimately, viable lessons can be drawn from the research of Antarctic subglacial environments given the uncovering of reliable sanitary methodologies that are going to be required during future approaches and sampling of natural systems of extraterrestrial subglacial environments in order to minimize irreparable anthropogenic disturbances on any potential astrobiology. Regardless of the question if the future investigation of Europa’s and Enceladus environments is going to reveal astrobiology within beneath their icy surfaces; this investigation is going to be of invaluable information for the improving familiarity of physical systems beyond Earth. / Sedan länge har forskare vetat att flytande/rinnande vatten är en av de viktigaste förutsättningar för allt liv på Jorden. Under de senaste decennierna har frågan om liv på Jupiters måne Europa, och Saturnus måne Enceladus aktualiserats, efter upptäckten av frusna islager på deras månytor. Evidens från respektive månars omloppsbanor, gör att forskare idag tror att månarnas djupa islager hettas upp inifrån av en aktiv, inre geologi, vilket i sin tur kan tyda på större mängder av flytande vatten. I och med omvandlingen av is till flytande vatten, får detta forskare att tro att cirkulationen av vatten, ihop med den aktiva geologin, möjligtvis har skapat och upprätthåller beboliga förutsättningar för mikroskopiskt liv. I dagsläget planeras ett flertal satelliter skjutas upp till månarna med uppdrag att bekräfta fallet om flytande vatten och beboliga miljöer på månarna, och därmed även undersöka frågan om månarna möjligtvis bär på liv. På den frusna kontinenten Antarktis har ett flertal motsvarande subglaciala miljöer undersökts för att fastställa deras kvalifikationer att upprätthålla liv under extrema levnadsförhållanden. Under dessa undersökningar har ett flertal mikroorganismer påträffats i prover från iskärnor från två subglaciala sjöar (Vostoksjön och Whillanssjön), varav några blivit omstritt påstådda som inhemska extremofiler. Ifall detta stämmer, betyder det att de två subglaciala sjöarna underhålls av ett unikt samspel av drivande faktorer som upprätthåller de nödvändigaste levnadsförutsättningarna för att mikroorganismer kan överleva, även frodas i uppenbart extrema miljöförhållanden. Med forskningen av Antarktis subglaciala sjöar som rapporterar ett unikt samspel mellan is, vatten och underliggande geologi; kan den fortsatta fastställningen av detta fysiska samspel, samt vidare identifikationer av inhemska mikroorganismer att bli en viktig lärdom för framtida satelliters datainsamling av subglaciala vattenmiljöer på Europa och Enceladus. För att underlätta och effektivisera sökandet efter potentiella livsmiljöer, samt möjligtvis hitta utomjordiskt liv på isiga månar bör framtidens satellituppdrag dra stor lärdom och väga in de erfarenheter och resultat som gjorts på subglaciala sjöar i Antarktis.

The thesis contains a survey of numerical tools for studying thermomechanical interactions of a two-phase system contained in a domain with an upper bound- ary that forms a free surface. The enthalpy diffused-interface formulation is used for an approximation of the phase change interface and the computing algorithm is benchmarked against an analytical solution of the Stefan problem. Arbitrary Lagrangian-Eulerian kinematical description of the continuum is applied to over- come the difficulty in the form of the free surface. The validity of the approach is examined on a thermal convection benchmark problem. 1

No description available.

La glace de H2O est présente dans de nombreux environnements planétaires, et notamment sous forme de polymorphe de haute pression au sein des satellites de glaces ainsi que dans le manteau des planètes extrasolaires, dites planètes océan. La diversité des conditions thermodynamiques prédite au sein de ces corps planétaires a souligné le besoin de nouvelles données de laboratoire et de calculs sur les glaces de H2O afin de pouvoir modéliser leur évolution et leur structure interne.Si les propriétés structurales et spectroscopiques des pôles purs de ces glaces sont déjà relativement bien connues, une description pétrologique plus réaliste des solutions solides et des phases riches en impureté, manque encore à la communauté. Ce travail de thèse s’est concentré sur l’étude de la fusion des glaces VI et VII dans le binaire H2O-NaCl grâce aux techniques de cellules à enclumes en diamants et la spectroscopie vibrationelle Raman. Ces données ont été complétées par des mesures du fractionnement du sel analogue RbI entre les glace VI et VII et le fluide aqueux en utilisant la cartographie de fluorescence X et de diffraction des rayons X réalisées à l’European Synchrotron Research Facility (Grenoble). Ceci as permis de mettre en évidence une inversion de densité entre le fluide riche en sel et la glace VI et de révéler une forte différence de partage du sel entre la glace VI et la glace VII avec un coefficient de partage du RbI estimé à Kd(VI-VII)=4.5(±2.7)10-2.Au sein des plus gros corps riches en H2O appelés planète océan, le manteau de glace potentiellement épais de plus de 1000 km abrite un type de glace de ultra haute pression appelé glace X. Cette phase de la glace d’eau est unique de part sa structure cristallographique ionique, contrairement aux autres glaces de plus basse pression, toutes de structure moléculaire. Cette caractéristique structurale et l’absence de données concernant ses propriétés mécaniques ont motivé l’étude de ses propriétés élastiques et plastiques. Ainsi à partir de calcul ab initio et du modèle de Peierls Nabarro, j’ai pu déterminer une forte variation de l’anisotropie élastique avec la pression, les différentes structures de cœurs des dislocations vis et coin et les systèmes de glissement préférentiels au sein de la glace X dans son champ de stabilité de 100 à 350 GPa. Nos calculs suggèrent que la déformation de la glace X est toujours localisée sur le plan {110} et que le système <110>{110} contrôle la déformation plastique en dessous de 250 GPa et que le système <100>{110} est dominant à plus haute pression. Nos résultats montrent aussi que si l’anisotropie élastique augmente rapidement avec la pression, la plasticité de la glace X devient quasi-isotrope à 350 GPa. / H2O ice is found in a variety of planetary environments, notably in the form of high pressure polymorphs inside icy moons and extrasolar ocean planets. The great diversity of thermodynamic conditions predicted inside such planetary bodies, reveals the need for new experimental and computational data to allow modeling of their internal structure and dynamics.Structural and spectral properties of H2O pure ices have been intensively studied, but surprisingly there is a lack of petrological data on impurities rich ice solid solutions. This Ph.D. thesis work focused on the study of ice VI and ice VII fusion curves in the H2O-NaCl binary, using diamond anvil cell and Raman spectroscopy. We later determined the partitioning of the NaCl analog salt, RbI, between ice VI and VII and the aqueous fluid using X- ray fluorescence and X-ray diffraction techniques at the European Synchrotron Research Facility (Grenoble). Our results enable us to observe a density inversion between ice VI and the salty fluid, and to measure a strong difference in salt partitioning between ice VI and ice VII with a partition coefficient of Kd(VI-VII)=4.5(±2.7)10-2. Inside the largest H2O rich planetary bodies, called ocean planets, the icy mantle, putatively more than 1000 km thick, shelters an ultra high pressure ice form called ice X. This H2O ice phase is unique because of its ionic crystallographic structure, in contrast with lower pressure ices polymorphs, all being molecular solids. This characteristic coupled with the fact that no data are available yet on its mechanical properties, encouraged us to study its elastic and plastic properties. Using ab initio calculations and the Peierls Nabarro model, I showed the strong variation of elastic anisotropy with increasing pressure and determined the dominant slip system inside the structure of ice X over its entire pressure stability range from 100 to 350 GPa. Our calculations suggest that plasticity in ice X is dominated by displacement always occurring on the {110} glide plane. Also, it reveals that the <110>{110} glide system is dominant below 250 GPa and that the <100>{110} slip system controls the plasticity of ice X. Our results also show that, if elastic anisotropy of ice X is strongly increasing with increasing pressure, the plasticity becomes almost isotropic at 350 GPa.

In July 2031, a new chapter in the exploration of the Jovian system will begin with the arrival of the Jupiter Icy Moons Explorer (Juice) at Jupiter. Launched on April 14 2024 as part of ESA’s Cosmic Vision programme, the mission aims to study Jupiter and its icy Galilean moons Callisto, Europa, and Ganymede. Juice carries a whole suite of instruments for in-situ and remote ground observations, one of which is the Jovian plasma Dynamics and Composition analyser (JDC). As a part of the Particle Environment Package (PEP), the particle detector will measure the energy, mass, charge and arrival direction of ions and electrons in the Jovian magnetosphere. Spacecraft charging caused by interactions between the spacecraft and its surrounding plasma environment poses a significant problem for JDC because the electrostatic potential of the spacecraft accelerates/decelerates charged particles, resulting in distorted measurements, particularly for the lowest energy particles.  In this report, we show the results of spacecraft charging and instrument simulations performed in the Spacecraft Plasma Interaction System (SPIS) for the solar wind and Earth’s magnetosheath—two environments that Juice will encounter at the start of the cruise phase. We found that the conductive surfaces that cover the majority of the spacecraft become positively charged as a result of a large photoelectron current in both the solar wind and magnetosheath environments. We show that these surfaces are expected to reach potentials of 9 V in the solar wind and 4 V in the magnetosheath. The four radiators on Juice that are covered with dielectric paint and shaded by the sun shield become negatively charged in both simulated environments. The radiator potentials can be as low as -40 V in the solar wind and -100 V in the magnetosheath. We also conclude that due to blocking by the spacecraft main body, the ion population cannot be sampled in the solar wind unless a spacecraft roll is performed. Furthermore, due to the high ion f low energy, spacecraft charging will not influence JDC measurements in this environment.  In the magnetosheath, the ion population can be sampled by JDC, and we identified three distortion mechanisms: (1) repulsion by the main body, (2) attraction by two of the radiators, and (3) repulsion by the MAG boom. Of all the distortion modes, the one originating from a negatively charged (-67.8 V) radiator close to JDC is the strongest, affecting ions with energies above 80 eV. The least powerful but most prevalent mode is the repulsion of ions by the main body. Our results can be compared with future in-situ measurements to identify distortion mechanisms well ahead of the science phase in which the scientifically important measurements will be carried out.