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International audience; The Curiosity rover of the Mars Science Laboratory has been exploring since mid-2021 the lower sulfate unit of Mount Sharp in the Gale crater. This unit, first described from orbital observations as showing spectral signatures of hydrated sulfate minerals [1], has recently been revealed to record amajor paleoenvironmental and climatic transition during the Hesperian-Noachian transition, with the onset of alternating wet and dry conditions before a complete aridification of Martian conditions [2]. Before the current campaign, this unit was mainly studied using remote observations (e.g., [2, 3]), but Curiosity has now entered this major interval allowing to precisely study the rock record leadingto this major climatic event. Since the rover left the Glen Torridon area (aka the clay-bearing unit, Fig. 1), the Curiosity rover entered the sulfate-bearing unit (~Sol 3100, mid-2021; Fig. 1) and traversed sedimentary series mainly composed of fine to coarse sandstones. While no clear facies change or sharp contact hasbeen observed when entering the sulfate-bearing unit, these levels differ from the previously observed terrains in Gale by an increased occurrence of nodular features with a strong sulfate geochemical signature [4, 5], polygonal ridges [4], or even halite detections [6]. Otherwise, thesedimentary structures and grain-size are continuous across the upper members of the Carolyn Shoemaker formation and into the overlying Mirador formation, indicating a likely continuity in the continental settings for most of these deposits.

International audience; Gale crater on Mars records a large section of sedimentary rocks, mainly represented by the 5-kmthicksequence of Mount Sharp (Aeolis Mons). The lower part of this sequence has been explored bythe Curiosity rover of the Mars Science Laboratory (MSL) mission, revealing lacustrine to fluvialdepositional sequences [e.g., 1] bearing clay minerals [2]. Orbital observations highlighted thepresence of clay minerals at the base of Mt Sharp but also hint at a major wet to dry environmentalchange with clay-bearing rocks giving way to several hundred of meters of sulfate-bearing strata [3,4]. Orbital data coupled with rover-based observations revealed that the sulfate-bearing unit recordcoincides with a major change of depositional environment followed by alternation of wetter anddrier conditions rather than a monotonous aridification during the Hesperian epoch [5].Before Curiosity reached this part of Gale crater, those observations were supported using longdistanceimaging capabilities of the Remote Micro-Imager (RMI) sub-system of the ChemCaminstrument [6]. With a focal length of 700 mm, the RMI telescope complements the color Mastcamimagers with higher spatial resolution views of sedimentary structures and textures of rocksoutcropping several hundred meters up to a few kilometers away from the rover (a ~60 km-recordobservation having recently been achieved, [7]). This capacity is therefore used by the MSL teamboth to plan future guidance of the rover and to observe geologic features from a distance. Theselong-distance observations pointed at the sulfate-bearing unit reveal the presence of sub-metricscalecross-stratifications and deflation surfaces as well as diagenetic features (e.g., “satin spar”;Fig. 1). While their size allows for long-range remote observation (i.e., several hundred meters awayusing imagers onboard the rover, Mastcam and RMI), the resulting images lacks depth due to thedistance. Yet, such 3D information can be critical in characterizing and understanding thesedimentary processes behind the setting of these structures.To improve our observations, we are conducting an imaging experiment to reconstruct the 3D shapeof the sulfate-bearing unit outcrops with Structure-from-Motion photogrammetry using ChemCam’sRMI frames. This method is usually performed on close-range geologic features observed with otherimagers onboard the rover (MAHLI, Mastcam, Navcam, [8]), but such an approach had never beenapplied to long-distance RMI frames. Here, we apply photogrammetric treatment to specific sets ofrepeated long-distance observations on the sulfate-bearing unit. To cope with the high distance ofthe target, we use a several-hundred meters “virtual baseline” represented by successive positionsof the rover along its traverse. Figure 1 shows one of the two long-distance (1x12) RMI mosaics(ccam04947, taken on Sol 2947, cf. Fig. 2) which served as input in the stereoscopic test. Thismosaic illustrates an outcrop of the sulfate-bearing unit situated ~650 meters away from the roverat that time (Fig. 2). A second similar mosaic pointed at the same target was taken on Sol 2962(2x16 RMI mosaic, ccam04962) after the rover drove about 200 meters southeastwards (Fig. 2).able to reconstruct the shape of the outcrop. The resulting 3D model presented in Figure 3 revealsthe actual 3D shape of the imaged outcrop situated several hundred meters away from the rover, aswell as displaying with improved accuracy the spatial distribution of the sedimentary and/ordiagenetic structures. The use of this technique to produce long-distance 3D models will have criticalimplication in helping to assess and to characterize the depositional conditions related to the sulfatebearingunit, a key objective of the Curiosity rover. The use of these models could also serve to helpplanning the upcoming exploration of this interval by designating high-interest targets. We also lookforward to applying this method to long-distance color images obtained with the more advancedcolor RMI subsystem of the SuperCam instrument onboard the Perseverance rover currentlyoperating in Jezero crater [9, 10].

International audience; Since 2012, the Mars Science Laboratory Curiosity rover has studied the sedimentary deposits within the Gale Crater, leading to the description of varying lacustrine to fluviatile and fluvio-deltaic environments. Here, we focus on the sedimentary record of the Kimberley outcrop traversed by Curiosity between sols 603 and 630. This section presents siliciclastic rocks with an unusually high potassic content (Le Deit et al., 2016, JGR-Planets). However, poorly constrained architecture and stratigraphic relations between the series of the Kimberley Formation and their local to regional surroundings still 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 the area to characterize the contacts observed on the outcrop itself and in its immediate vicinity, but also for a new assessment of the precise nature and morphology of the sedimentary structures and their spatio-temporal distribution throughout the outcrop and beyond. We therefore propose to use a true color highly resolved Digital Outcrop Model (DOM) of the Kimberley outcrop, obtained using Mars Science Laboratory imagery, integrated into a Virtual Reality (VR) environment (Caravaca et al., in press, PSS). Taking advantage of this "in situ" geological analysis of the 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 with an unprecedented precision. We notably observe and describe both conformable and unconformable contacts over the entire outcrop, but also several sets of varying scale cross-stratifications (from cm-to pluri-meter scale). These results are in accordance with a fluviatile hydrodynamically active system. They tend to corroborate the idea of a complex yet diachroneous evolution of the area, with the possibility of laterally evolving depositional settings, spanning a significant amount of time. Powered by TCPDF (www.tcpdf.org)

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.

International audience; The Mars Science Laboratory (MSL) Curiosity rover completed a detailed investigation at the Kimberley waypoint within Gale crater from sols 571-634 using its full science instrument payload. From orbital images examined early in the Curiosity mission, the Kimberley region had been identified as a high-priority science target based on its clear stratigraphic relationships in a layered sedimentary sequence that had been exposed by differential erosion. Observations of the stratigraphic sequence at the Kimberley made by Curiosity are consistent with deposition in a prograding, fluvio-deltaic system during the late Noachian to early Hesperian, prior to the existence of most of Mount Sharp. Geochemical and mineralogic analyses suggest that sediment deposition likely took place under cold conditions with relatively low water-to-rock ratios. Based on elevated K 2 O abundances throughout the Kimberley formation, an alkali feldspar protolith is likely one of several igneous sources from which the sediments were derived. After deposition, the rocks underwent multiple episodes of diagenetic alteration with different aqueous chemistries and redox conditions, as evidenced by the presence of Ca-sulfate veins, Mn-oxide fracture fills, and erosion-resistant nodules. More recently, the Kimberley has been subject to significant aeolian abrasion and removal of sediments to create modern topography that slopes away from Mount Sharp, a process that has continued to the present day.

The Windjana drill sample, a sandstone of the Dillinger member (Kimberley formation, Gale Crater, Mars), was analyzed by CheMin X‐ray diffraction (XRD) in the MSL Curiosity rover. From Rietveld refinements of its XRD pattern, Windjana contains the following: sanidine (21% weight, ~Or95); augite (20%); magnetite (12%); pigeonite; olivine; plagioclase; amorphous and smectitic material (~25%); and percent levels of others including ilmenite, fluorapatite, and bassanite. From mass balance on the Alpha Proton X‐ray Spectrometer (APXS) chemical analysis, the amorphous material is Fe rich with nearly no other cations—like ferrihydrite. The Windjana sample shows little alteration and was likely cemented by its magnetite and ferrihydrite. From ChemCam Laser‐Induced Breakdown Spectrometer (LIBS) chemical analyses, Windjana is representative of the Dillinger and Mount Remarkable members of the Kimberley formation. LIBS data suggest that the Kimberley sediments include at least three chemical components. The most K‐rich targets have 5.6% K2O, ~1.8 times that of Windjana, implying a sediment component with >40% sanidine, e.g., a trachyte. A second component is rich in mafic minerals, with little feldspar (like a shergottite). A third component is richer in plagioclase and in Na2O, and is likely to be basaltic. The K‐rich sediment component is consistent with APXS and ChemCam observations of K‐rich rocks elsewhere in Gale Crater. The source of this sediment component was likely volcanic. The presence of sediment from many igneous sources, in concert with Curiosity's identifications of other igneous materials (e.g., mugearite), implies that the northern rim of Gale Crater exposes a diverse igneous complex, at least as diverse as that found in similar‐age terranes on Earth.

Most fluvial and lacustrine landforms on Mars are thought to be old and have formed more than ~3.8 Gyr ago, in the Noachian period. After a major climatic transition, surface liquid water became less abundant and finally disappeared almost completely. Recent work has shown that observational evidence for Hesperian and Amazonian aqueous processes is more common than previously recognized, but their nature is poorly understood. Moreover, it is not clear how the paleoclimate of Mars can be constrained by this activity. Here we report our investigation of a population of deltas around the ancient impact basin Chryse Planitia. To test whether the results are globally applicable, we also studied selected deltas with similar morphologies in the eastern hemisphere and found that the results are consistent. We compared the morphology of deltas, feeder channels, and receiving lakes, dated deltas by crater counting and searched for alteration minerals in hyperspectral images. The valleys and associated late-stage deltas were formed by short-lived aqueous processes, as suggested by their morphology and the general lack of associated aqueous alteration minerals. The likely source of water was neither widespread precipitation nor a regionally connected groundwater aquifer, but water mobilized locally from the cryosphere. Delta formation in our study areas occurred from the Early Hesperian to the Late Amazonian and did not require sustained periods of global climatic conditions favoring widespread precipitation. Liquid surface water has been locally present on Mars even after the Noachian, although only episodically, for transient intervals, and widely separated in space.

International audience