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International audience; Jezero crater has been selected as the landing site for the Mars 2020 Perseverance rover, because it contains apaleolake with two fan-deltas, inlet and outlet valleys. Using the data from the High Resolution Stereo Camera(HRSC) and the High Resolution Imaging Science Experiment (HiRISE), we conducted a quantitative geomorphological study of the inlet valleys of the Jezero paleolake. Results show that the strongest erosion is related to a network of deep valleys that cut into the highland bedrock well upstream of the Jezero crater and likely formed before the formation of the regional olivine-rich unit. In contrast, the lower sections of valleys display poorbedrock erosion and a lack of tributaries but are characterized by the presence of pristine landforms interpreted asfluvial bars from preserved channels, the discharge rates of which have been estimated at 10^3–10^4 m^3s^-1. The valleys’ lower sections postdate the olivine-rich unit, are linked directly to the fan-deltas, and are thus formed inan energetic, late stage of activity. Although a Late Noachian age for the fan-deltas’ formation is not excludedbased on crosscutting relationships and crater counts, this indicates evidence of a Hesperian age with significantimplications for exobiology.

International audience; The Kimberley outcrop, traversed by Curiosity in 2014, shows a siliciclastic depositional record with an unexpectedly high potassic content. However, its intra-and inter-formational relations are still poorly constrained yet critical to understand the paleoenvironmental implication of this geochemical anomaly. To answer these questions, we use a high-resolution Digital Outcrop Model integrated into a Virtual Reality environment. We therefore characterize multi-scale sedimentary features, highlighting laterally evolving depositional conditions.

International audience; Since 2012, the Mars Science Laboratory rover Curiosity has studied the sedimentary record of the Gale Crater. This work focuses on the sedimentary record of the Kimberley outcrop, traversed by Curiosity between sols 603 and 630. This section presents siliciclastic rocks with anunusually high potassic content (Le Deit et al., JGR-Planets, 2016). However, poorly constrained stratigraphic relations between the series of the Kimberley Formation and their local to regional surroundings prevent further understanding of the exact extent of these accumulations andtheir significance within the broader Gale Crater paleoenvironmental scheme. Such questions highlight the need for a new finer mapping of the area to notably characterize the precise nature and morphology of the sedimentary structures and contacts observed on the outcrop itself and in its immediate vicinity. We therefore propose to use a true color highly resolved (up to the mm-scale) Digital Outcrop Model (DOM) of the Kimberley outcrop, obtained using Mars Science Laboratory imagery, integrated into a Virtual Reality (VR) environment. Taking advantage of purposely-developed measurement tools dedicated to the VR exploration and “in situ” geological analysis of DOM, we were able to observe and characterize such sedimentary structures and contacts, as well as their spatial extension throughout the reconstructed area of Kimberley.This new edge technique allows us to observe and describe with unprecedented precision both conformable and unconformable contacts, and several set of varying scale cross-stratifications (from cm- to pluri-meter scale). These results tend to corroborate the idea of a complex anddiachroneous evolution of the area, with the possibility of laterally evolving depositional settings, spanning a significant amount of time.Newly developed tools in Virtual Reality therefore give us the opportunity to study “in situ” digital reconstructions of Martian outcrops such as Kimberley and represent a major advance for the characterization and interpretation of remote planetary past paleoenvironments.

International audience; Reconstruction of highly-resolved Digital Outcrop Model (DOM) using Structure-from-Motion photogrammetry is a low-cost but very effective method to explore and study remote planetary outcrops. Extensive data gathered by Mars Science Laboratory (MSL) rover Curiosity can be used to produce models of specific outcrops visited by the rover in the Gale Crater, on Mars. Integration into a Virtual Reality (VR) environment of these DOM enables one or several users to experience a reliable and realistic depiction of the actual geometries of the geological features, which is usually prevented by classic viewing methods on computer screens. Also, use of a VR environment authorizes the observation at real scale of various sedimentary series, structures and objects present at an outcrop, the same way they would on a real field. Moreover, this practice allows for a very precise and accurate characterization, description and therefore mapping of the features, as well as the contextualization of the sampling and remote analyses underwent by the Curiosity rover within their geological setting (e.g. ChemCam Laser-Induced Breakdown Spectrometer and Remote Micro-Imager data). Here, we focus on the Kimberley outcrop, traversed by Curiosity in 2014 between martian sols 603 and 630. This section presents a sedimentary succession with unusually high potassic content (Le Deit et al., JGR-Planets, 2016). However, poorly constrained stratigraphic relations between the series of the Kimberley Formation and its local to regional surroundings prevent further understanding of the exact extent of these accumulations and their significance within the broader Gale Crater paleoenvironmental scheme. Such questions highlight the need for a new finer mapping of, first, the outcrop itself to notably achieve precise characterization at the cm-scale of the Mount Remarkable butte; and then of the various structures present in the immediate vicinity of the outcrop. We therefore propose to use a custom true color highly resolved (up to the mm-scale) DOM of the Kimberley outcrop integrated into a VR environment to achieve precise and accurate mapping of the area and of the different geomorphological and sedimentological features (beds, structures and contacts alike). This represents a first step toward a better understanding of the intra-and inter-formational relations of the Kimberley series. We acknowledge the EU H2020 PlanMap project for supporting this work.

International audience; Structure-from-Motion (SfM) photogrammetry is an efficient, low-cost and powerful method to reconstruct Digital Outcrop Models (DOM) only from a set of overlapping photos. Apparent displacement of similar points across the set are used to determine the position of these points within a 3D space, and therefore recreate the tri-dimensional geometry (3D mesh) of the photographed objects. This method has recently been explored for remote planetary exploration such as that of the Gale Crater, Mars, thanks to the extensive imagery data from the Mars Science Laboratory (MSL) rover Curiosity. Here, we reconstructed a DOM of the Kimberley outcrop, traversed by Curiosity between sols 603 and 630, based on a comprehensive set of multi-scale photos gathered by 3 different imaging instruments aboard Curiosity, namely the navigational cameras (NavCam, 530 photos), mast cameras (MastCam, 1443 photos) and the Mars Hand Lens Imager (MAHLI, 32 photos). Despite the difference in resolution, colorization (greyscale vs full color), coverage and overlap parameters across these three different image data, we were able to compute a highly resolved full color DOM of the Kimberley outcrop using Agisoft PhotoScan software. Moreover, use of PhotoScan's embedded advanced geospatial features allowed us to obtain a geographically constrained DOM and a direct and proper scaling of the model (validated using the rover's tracks on the model). As the Kimberley outcrop presents a sedimentary succession with unusually high potassic content (Le Deit et al., JGR-Planets, 2016), the stratigraphic relations within this series and with its immediate to local surroundings are critical to understand the extent of these potassic accumulations and their signification from a paleoenvironmental point of view. We therefore integrated this high-resolution DOM into a collaborative Virtual Reality (VR) environment. VR lets one or several users observe at real scale the various sedimentary series and structures of the outcrop. This way, precise and accurate description, quantification and mapping of the outcrop is possible, allowing for more precise characterization and interpretation, as well as enabling contextualization within the local geological setting of the various data gathered by Curiosity (e.g. ChemCam Laser-Induced Breakdown Spectrometer and Remote Micro-Imager data). Collaborative VR exploration and characterization of photogrammetrically reconstructed reliable DOM is paving the way for remote geological exploration of Martian outcrops and other planetary bodies in near future. We acknowledge the EU H2020 PlanMap project for supporting this work.

International audience; Structure-from-Motion (SfM) photo-grammetry is an efficient, low-cost and powerful method to reconstruct Digital Outcrop Models (DOM) and/or specific geological object, only from a set of pho-tos [1]. This method is particularly well-suited in remote planetary exploration such as that of Gale Crater, Mars, using extensive imagery data from the Curiosity rover mission [2]. Using a set of multi-scale images from 3 different instruments aboard Curiosity, we were able to compute a high-resolution and highly-detailed full color DOM of the Kimberley outcrop (sols 603-630), that was then integrated into a Virtual Reality (VR) environment for visualization and geological characterization.

Important sulfate deposits have been discovered in various equatorial regions of Mars : the canyons of Valles Marineris, chaotic terrains, and Meridiani plains. In order to explain the chemical composition of these deposits and the formation of such a large volume of sediments displaying the same composition and various and extensive terrains, one of the latest hypotheses suggests a glacial origin. The aim of this thesis is to evaluate the consistency of this hypothesis by an integrated morphological and mineralogical study of sulfates found on the North Polar Cap and on equatorial chaotic terrains (Aram Chaos). The analysis of the North Polar Cap reveals that all the superficial sediments contain gypsum. These sulfate-bearing particles have been released directly from the ice cap by sublimation. Winds are then responsible for the reworking of these sediments and their accumulation in the circumpolar dune field. The analysis of Aram Chaos sulfate deposits reveals some bright, layered outcrops, similar to those observed in Valles Marineris and in Meridiani Planum ; they contain a mixture of monohydrated sulfates, ferric oxides and hydrated minerals. These deposits could also originate from glacial processes because climate models and morphological analyses show that, during periods of high obliquity, ice accumulations can have formed in the lower latitudes. Moreover, the observation of terrestrial analogs in Antarctica demonstrates that sulfates can form in ice by post-depositional processes. These processes could reproduce the chemical composition of the Martian equatorial deposits if ice and some volcanic materials were accumulated at the same time.; D'importants dépôts de sulfates ont été découverts dans certaines régions équatoriales de Mars : les canyons de Valles Marineris, les terrains chaotiques, et les plaines de Meridiani. Afin d'expliquer la chimie de ces dépôts, ainsi que la formation d'un tel volume de sédiments de même composition, sur des surfaces aussi larges et variées, l'une des hypothèses les plus récentes suggère une origine glaciaire. Le but de cette thèse est d'évaluer la plausibilité de ce mode de formation, par une étude morphologique et minéralogique comparative des sulfates trouvés sur la calotte polaire Nord et sur les terrains chaotiques (Aram Chaos). L'analyse des sédiments superficiels de la calotte polaire montre que ceux-ci sont riches en gypse. Ces particules riches en sulfates proviennent directement de la calotte polaire, s'accumulent en surface par ablation de la glace, et sont transportées par le vent dans les dunes circum-polaires. L'analyse des affleurements observés à l'équateur sur Aram Chaos montre des dépôts stratifiés clairs, semblables à ceux de Valles Marineris et de Meridiani Planum ; ils contiennent un mélange de sulfates monohydratés, d'oxydes de fer et de minéraux hydratés. Ces dépôts pourraient également avoir une origine glaciaire car, durant les périodes de haute obliquité, d'anciennes accumulations de glace ont pu se former aux basses latitudes. De plus, l'observation d'analogues terrestres en Antarctique révèle que des sulfates se forment effectivement dans la glace par des réactions post-dépôt, et peuvent être compatibles avec la chimie des minéraux observés à l'équateur martien, si l'accumulation de la glace coïncide avec le dépôt de matériaux volcaniques.