Search

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 a major 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 leading to 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 has been 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, the sedimentary 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.Such structures are notably well visible at the Prow locality, a major outcrop situated in the Contigo member of the Mirador formation, just below the Greenheugh pediment (Fig. 1). This outcrop has been reached and studied in January and February 2022, between sols 3349 and 3379. Using ~3200 mid- and close-range images from the Navigation and Mast cameras (Navcam, Mastcam), we used structure-from-motion photogrammetry to reconstruct a Digital Outcrop Model (following the method described in [7]) of the Prow locality and its vicinity (Fig. 2). This DOM covers an area of about 1000m². Two small excerpts of this DOM are explorable online on the Sketchfab platform at https://skfb.ly/o8DJZ and https://skfb.ly/otpLW. The DOM allows us to visualize and characterize several sets of meter- to centimeter-scale sedimentary structures, over about 30 meters of lateral continuity, either using on-screen visualization, or integrated within a Virtual Reality environment.The DOM reconstruction has been helpful in determining the targets of interest during the Prow exploration by Curiosity. One particular benefit has been to identify the Toron block (Fig. 2) as a fallen piece of the main outcrop, allowing us to perform very close-range observations of the outcrop’s cliff-face (e.g., Fig. 3a) without actually putting the rover too close to the actual rock-face. The interest of using such 3D reconstruction notably lies in the ability to characterize the spatial distribution of the multi-scale structures observed at the Prow, but also to study the spatial distribution (and potential variations) of the geochemical composition of these layered sandstones as seen by the ChemCam instrument. We also take advantage of the high-resolution micro-images provided by the Remote Micro-Imager subsystem of the ChemCam instrument (with a field of view of 20 mrad per frame, resolving grains under the silt at close range) to study the facies (grain-size, micro-structures) of the different sandstone beds cropping out at this locality (Fig. 3).At the Prow, we characterize several sets of sedimentary structures such as (but not limited to) meter-scale cross-stratifications, cm-scale symmetric ripples but also probable climbing ripples (Fig. 3a). These structures, mostly indicating a direction of transport toward the NW (similar to what is observed in underlying Glen Torridon area), denotates sustained aqueous conditions compatible with a fluvial setting. We also observe in some place at the Prow, and notably in the upper layers, mm-scale fine-grained draping (Fig. 3b) deposited at the surface of (cross-)stratifications, reminiscent of flaser bedding on Earth. These fine muddy levels indicate recurrent intervals of low-energy deposition in-between higher-energy periods. Put together, these elements help us to characterize sustained aqueous conditions in a dynamic setting of combined flow and wave action at the time the sediments were deposited (e.g., [8]), helping us to determine probable mixed fluvio-aeolian settings around the critical climatic transition observed within this sulfate-bearing unit characterized by alternating wet and dry conditions.References: [1] Miliken et al., 2010, Geophys. Res. Lett. 37, L04201; [2] Rapin et al., 2021, Geology 49; [3] Caravaca et al., 2021, Remote Sensing, 13(20), 4068; [4] Rapin et al., 2022, EPSC, this meeting; [5] Schieber et al., 2022, LPSC, Abstract #1304; [6] Meslin et al., 2022, LPSC, Abstract #2492; [7] Caravaca et al., 2020, Planet. Space Science 182, 104808 ; [8] Gupta et al., 2022, ESPC, this meeting.

The Apollo 17 manned mission landed in the Taurus Littrow valley on the Moon in December 1972. The geology of this site, on the eastern edge of Mare Serenitatis, was thoroughly investigated during extra vehicular activities performed during three days spent at the surface [1, 2]. A total of 111 kg of well-documented rock and soil samples were collected and brought back to Earth during this last Apollo mission. Among several waypoints of interest, astronauts spent more than one hour to investigate five large boulder fragments at Station 6, lying at the base of a long boulder trail descending from the North Massif. These boulders might originate in material emplaced as a result from the ejected melt sheet from the Crisium impact event [2], or Serenitatis impact event [3, 4]. In a recent study [5], we used scanned photographs taken in situ with astronaut’s Hasselblad cameras to reconstruct a 3D model of each of the boulders using photogrammetry techniques [6]. In addition to the 3D reconstruction of the boulders themselves reported in [5], we pushed the reconstruction process one step further by taking advantage of the fact that the rock samples hammered from the boulders at Station 6 were thoroughly documented once brought back on Earth in the Lunar Receiving Lab facility in Houston. In particular, several stereoscopic photographic pairs were systematically acquired for a significant number of the samples. When a sufficient number of viewpoints have been acquired, this potentially allows a complete photogrammetric 3D reconstruction of the rocks themselves. We used as input original photographs available on the Lunar and Planetary Institute website (https://www.lpi.usra.edu/lunar/samples/atlas/). We first performed a color balancing of the scans of these photos. Then, masks corresponding to a detouring of the rocks were applied to avoid errors induced by the fixed background in the photogrammetric project. By manually adding tie points, we were able to compute a detailed textured 3D model of sample 76315 (a micropoikilitic impact melt breccia), sample 76215 (a vesicular micropoikilitic impact melt breccia), and sample 76015 (another vesicular micropoikilitic impact melt breccia, which was chipped off top corner of Block 5 of the big boulder at Station 6). The full reconstruction process is illustrated in Fig. 1 for sample 76215. We have posted the 3D models of these samples on the Sketchfab web platform at https://sketchfab.com/LPG-3D to allow their easy visual inspection. These 3D models are of particular interest as these lunar samples have been broken into multiple pieces after being photographed. The 3D numerical model can therefore be thought as a kind of historical heritage of the original rocks, which do not exist anymore in their original form. Using this reconstruction, we can obtain a copy of the shape of these original rocks using a 3D-Printer (Fig. 2). They can also be viewed using augmented reality, with a cellphone or a tablet, or even manipulated in virtual reality on Sketchfab using a VR headset (Fig 2). From a more scientific point of view, the 3D models theoretically allow to replace the samples in their original position and orientation directly on the 3D models of the original boulders themselves (Fig 3). This is of particular interest to retrieve the precise original orientation of the sample, to investigate for example the characteristics of coatings. On sample 76015, at least three different units show various degree of alteration, which can be correlated with the original position of the sample with respect to its environment. The upper sky-facing side is the most affected by space weathering effects, with a well-developed patina. On its lower edge, a less altered face protected by a crevice might correspond to a lower alteration degree developed during only 20 million years, the approximate age of the impact generating the fall of the boulders from the North Massif slopes according to radiogenic dating. References : [1] Wolfe, E.W. et al. Geologic investigation of the Taurus-Littrow Valley: Apollo 17 landing site. U.S. Geol. Survey. Prof. Pap. 1981, 1080, 225–280., 1981 [2] Schmitt, H.H. et al., Revisiting the field geology of Taurus-Littrow. Icarus 2017, 298, 2–33, doi:10.1016/j.icarus.2016.11.042, 2017. [3] Spudis, P. D., and G. Ryder, Apollo 17 impact melts and their relation to the Serenitatis basin, Proc. Lunar Planet. Sci. Conf., 12th, 133–148, 1981. [4] Hurwitz and Kring, Identifying the geologic context of Apollo 17 impact melt breccias, Earth and Planetary Science Letters, 436, 64–70, 2016. [5] Le Mouélic, S. et al. Investigating Lunar Boulders at the Apollo 17 Landing Site Using Photogrammetry and Virtual Reality, Remote Sensing, 12 (11), DOI: 10.3390/rs12111900, 2020. [6] Favalli, M. et al., Multiview 3D reconstruction in geosciences. Comput. Geosci. 2012, 44, 168–176, 2012.

Introduction Antoniadi basin is a 330 km diameter Noachian basin localized in the eastern Arabia Terra that contains a network of dendritic ridges. Branched, dendritic ridges, such as these can form by a variety of processes including the inversion of fluvial deposits, thus potentially highlighting aqueous processes of interest for understanding Mars’ climate evolution. Here, we test this hypothesis by analyzing in details data from Colour and Stereo Surface Imaging System (CaSSIS), High Resolution Imaging Science Experiment (HiRISE) and High Resolution Stereo Camera (HRSC). Age of landforms Antoniadi’s interior plains are filled by deposits interpreted to be Hesperian or younger and volcanic in origin, possibly coeval with the volcanic episodes of the nearby Syrtis Major Planum [1]. The dendritic ridges lie on these volcanic plains to the south of a 28 km-diameter well-preserved crater (Fig. 1). Although this crater predates the branched ridges it is devoid of any fluvial erosion and appears mostly similar to many fresh, Amazonian age craters. While some erosion has affected the ridges, there is no indication of exhumation of these ridges from putative layers above the current plains surface. The crater size frequency distribution of the volcanic plains gives a model age of 2.5±0.5 Gy, using diameters of 200 m to 2 km. Thus, the branched ridges are Early Amazonian or younger. Figure. 1: Four Cassis images projected on CTX mosaic. The fresh crater to the north has been covered by fresh lava flows which themselves have been covered by the dendritic features. Morphometry and topography Individual ridges are easily recognizable with their dark tone in visible images compared to surrounding plains (Fig. 2), which display a slightly lighter tone. The ridges are organized as a dendritic network reaching a Strahler order of 4, i.e. the degree of hierarchy from the primary branches counting the number of junctions. Assuming tributary flows, this organization indicates a northward flow direction. However, the local slope is of 0.2° toward South, and thus contrary to the apparent network organization (assuming tributary flows). The branched ridges are also present on some of the lowest areas of these plains, but there is no evidence of terminal fans nor of erosional features affecting the plains in their more elevated areas. The texture of ridges at HiRISE scale (25cm/pixel) is rubbly with the occurrence of blocks up to ~1 m in size and a complete lack of layering in all HiRISE images where they are present unlike sedimentary strata usually observed within inverted channels on Mars. A HiRISE elevation model shows that branched ridges are between 1-5 m high, although erosion can explain some variations in height among the ridges. Ridges are up to 10 km long and 10-200 m wide without any obvious trends in width, i.e. ridges are not wider with increasing Strahler order. The order 1 branches are also peculiar in plan-view shape. They frequently display lobate shapes and are up to 100 m wide, which is wider than the ridge measured after the junction with several order 1 branches. North of the main pattern, a 500 m wide sinuous ridge present in the middle of the plain displays the same internal texture (rubbly) suggesting that it formed by the same process (white arrow at the top of Fig. 1). Figure 2: Close-up on the dendritic network with CaSSIS images. Conclusion Previous assessments of these landforms favored an origin as inverted channels [2]. Yet, our observations show many inconsistencies with this interpretation: (i) The rubbly texture lacks any layering at meter scale, a typical feature of inverted channels observed elsewhere on Mars [e.g., 3, 4]. (ii) The order 1 branches display a lobate shape and a larger width than higher order branches unlike river flows as observed on Earth. (iii) There is no increase in width from degree 1 branches of the network towards the north as would be expected for channels with increasing discharge rates downstream. (iv) The slope towards the south is contrary to the inferred flow direction to the north assuming a tributary network. Wrinkle ridges may be evidence for post-depositional changes in topography, but these uplifts appear localized (Fig. 1). Thus, the detailed analysis of these branched ridges shows characteristics difficult to reconcile with inverted fluvial channels. Subglacial drainages are known to locally flow against topography, but rarely display a dendritic pattern [5]. Assuming that deposition occurred along the current slope from north to south, the organization of the network requires a control by distributary channels rather than tributary channels. Distributary fluvial channels are possible for fluvial flows, but generally limited to braiding regimes or deltaic deposits, of which no further evidence is observed here. The lobate digitate shapes of the degree 1 branches are actually more in line with deposits of viscous flows, thus as terminal branches (Fig. 3). Such an interpretation is consistent with lava flows or mudflows that formed along the current topography. This conclusion would explain the presence of these landforms in an Early Amazonian plain lacking any evidence of fluvial activity, including the fresh crater that is stratigraphically older than the landforms studied. Acknowledgments: French authors are supported by the CNES. The authors wish to thank the spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA’s PRODEX. The instrument hardware development was also supported by the Italian Space Agency (ASI) (agreement no. I/018/12/0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the Univ. of Arizona (Lunar and Planet. Lab.) and NASA are gratefully acknowledged. References : [1] Tanaka K. L. et al. (2014) USGS map 3292. [2] Zaki et al. (2019) EPSC-DPS2019-244-1. [3] Burr et al. (2010) JGR-Planets, 115, E07011. [4] Mangold et al. (2008) JGR-Planets, 113, E08009. [5] Menzies, J (2002), Modern and Past Glacial Environments, Oxford.

Over the past 10 years, the Mars Science Laboratory (MSL) rover Curiosity has been investigating the plains of Aeolis Palus and the lower reaches of Aeolis Mons (informally known as Mount Sharp), a 5 km tall mound of sedimentary rocks in Gale crater (Figure 1). After traversing 27 km and nearly 600 m of vertical stratigraphy, three lithostratigraphic groups have been identified: Bradbury, Mount Sharp, and Siccar Point (SP). The Bradbury group consists of fluvial, deltaic, and lacustrine sedimentary rocks [1-2]. The Mt. Sharp group mainly consists of laminated mudstones with minor fluvial sandstones, interpreted as evidence of a long-lived lacustrine environment [1]. Locally, exposures of the Mt. Sharp group are unconformably overlain by aeolian cross-bedded sandstones of the SP group, interpreted to have deposited on an aeolian deflation surface [3]. While these three groups show evidence of deposition in specific environmental and climatic conditions, knowledge of their stratigraphic relationships is a key information to understand the evolution of environmental conditions in Gale. Yet, no clear stratigraphic contact has been observed at the boundary between the Bradbury and the Mt. Sharp groups. Because the mean dip of the Bradbury group is approximately horizontal, the MSL team suggested that the Bradbury group might be stratigraphically lower than the Mt. Sharp group, and therefore lower than the SP group [1]. Nonetheless, orbital analyses of the region suggested that capping strata of the Bradbury group could be part of the SP group [4]. Chemical data from the ChemCam and APXS instrument suites of Bradbury and SP group rocks have recently shown that both groups have similar compositions and possibly similar sediment sources [5-8]. In this study, we aim to reappraise the stratigraphic and chemical relationships between the Bradbury and SP groups using Mastcam [9-10] and ChemCam data [11-12] to characterize the evolution of Gale’s ancient environment. Lithostratigraphy of Zabriskie Plateau One of the best candidates to assess the potential contact between Bradbury and SP group rocks is located at the Zabriskie Plateau outcrop in the Pahrump Hills area (Figure 1). To better appreciate the facies and 3D geometry of the contacts, this outcrop has been reconstructed as a Digital Outcrop Model (Figure 2, https://skfb.ly/o9ZAq) [13]. In this model, we observe that most of the outcrop is composed of fine to medium-grained sandstones, arranged in dm- to meter-scale cross-stratifications, similar to some of the aeolian facies of the SP group [3]. These sandstones exist as “capping rocks” similar to previously described examples [4], suggesting that they are locally well-cemented on the topmost meter. Near the base of the DOM, we observe a meter-scale, ~30-cm thick, cross-stratified lens-shaped interval of coarser medium to pebble conglomerate. This level represents deposition under energetic aqueous conditions to transport clasts up to the pebble size, more likely to pertain to a fluvial channel. Interestingly, this conglomerate interval is at similar elevation (within one meter) to the surrounding sandstones, with no apparent unconformity, likely evidencing a conformable emplacement of this level within the finer sandstone succession. This would argue that the conglomerate level was deposited synchronously with the finer-grained sandstones during the same depositional event. Chemical composition of Bradbury and Siccar Point groups The average compositions of Bradbury and SP group rocks are overall quite similar (Table 1), and clearly distinct from Mount Sharp group rocks (Figures 3 and 4). By analyzing the rock compositions of Bradbury and SP groups, we sorted them into five major chemical groups, which are, in order of increasing average K2O/Na2O ratio and average K2O content for groups 1 to 4: group 1 has a basaltic composition; group 2 has low SiO2, intermediate TiO2, high FeOT and Na2O contents; group 3 has low CaO, high TiO2, FeOT, and K2O contents; group 4 has low TiO2 and Al2O3, and very high K2O contents; and group 5 has a composition close to group 1 with higher SiO2 and alkali contents (Table 1, Figure 3). Overall, the MgO and Al2O3 contents are quite variable. The composition of these rocks suggests mixing between mafic minerals and feldspars, including alkali feldspars in various proportions (Figure 4). Interestingly, both Bradbury and SP rocks occur in the first three chemical groups, which suggests similar source rocks for both groups of at least two types: a relatively low-potassium basaltic rock and a potassic-rich rock. The relative abundance of potassic-rich source rock in the mixture is interpreted to increase from group 1 to group 4. Besides, Bradbury and SP group rocks have a low Chemical Index of Alteration (CIA), which is indicative of limited chemical weathering (Figure 4). Conclusion 3D observations in the Pahrump Hills area suggest that Bradbury and Siccar Point units are intermingled and synchronous in an environment allowing fluvial episodes to occasionally occur among a drier setting, as observed on Earth [14]. This is consistent with the chemical compositions of Bradbury and Siccar Point groups which suggest similar source rocks in different relative abundances. This relationship implies that the Bradbury group could be younger than Mount Sharp group (Figure 5). To summarize, these observations are in favor of a common origin for both Bradbury and Siccar Point as a single clastic group, representing a temporal evolution from clement conditions during the deposition of Mount Sharp group to a colder and drier environment with still transient episodes of fluvial activity during the deposition of Bradbury and Siccar Point groups. [1] Grotzinger et al., Science 2015. [2] Mangold et al., JGR 2016. [3] Banham et al., Sedimentology 2018. [4] Williams et al., Icarus 2018. [5] Bedford et al., Icarus 2020. [6] Bedford et al., JGR 2022. [7] Thompson et al., LPSC 2022. [8] Thompson et al., this conference. [9] Malin et al., LPSC 2010. [10] Bell et al., Earth and Space Science 2017. [11] Wiens et al., Space Sci Rev. 2012. [12] Maurice et al., Space Sci. Rev. 2012. [13] Caravaca et al., PSS 2020. [14] Newell, Marine and Petroleum Geology 2001.

For more than a year now, the Perseverance rover of the Mars2020 mission has been exploring the Jezero crater in the northern hemisphere of Mars. This landing area was notably selected due to the presence of a large-scale fan-shaped sedimentary edifice in its western part at the mouth of Neretva Vallis (NV, Fig. 1a, e.g., [1]), that was interpreted to be a fossil deltaic system. Upon arrival in the crater in February 2021, remote observation from the ground were performed, allowing to answer this question with long-distance imaging using Mastcam-Z and SuperCam’s Remote Micro-Imager. Indeed, these observations allowed to identify with certainty structures characteristic of a Gilbert-type delta, confirming the fluvio-deltaic origin of this western fan [1]. In this work, we focus on the Kodiak butte (Fig. 1b) situated ~1 km away from the current main delta front. This butte exhibits Gilbert-type structures of bottomsets, foresets and topsets characteristic of the deltaic suite, and as therefore been identified as being a remnant of a past distal extension of the western delta [1; 2]. This butte was imaged from the east during the earliest part of the mission (Fig. 2a), but we also took advantage of the “Rapid Traverse” route to the delta foot to gather images of its northern-facing side (Fig. 2b), giving us data to study the 3D geometry of the sedimentary rocks that make this butte. Here, we provide an overview of the facies and stacking pattern of the deltaic series observed at Kodiak. We use both 2D high-resolution image data acquired by Mastcam-Z and SuperCam’s RMI instruments, but also 3D Digital Outcrop Model (DOM) reconstructed from RMI remote observations (e.g., [2], visible online at: https://skfb.ly/o89yU). While both views help us in determining the stratigraphic architecture of the butte, the later being critical in assessing with more precision the sediment transport directions, and especially their temporal variations within distinct units [2]. That is, we are able to describe at least two main depositional episodes recorded at Kodiak, with Delta Units 1 and 2 (Fig. 2). Both units are characterized by a well-evidenced Gilbert-type succession of bottomsets, foresets and topsets, of a similar size and extension. The lower elevation and position further north of Delta Unit 1 (Fig. 2) indicates that it predates Delta Unit 2. An overall direction of transport toward the south-west is observed for this unit from the dip of foresets observed from both east and north faces. Delta Unit 2 was observed in the first part of the mission, when the rover was positioned about 2 km away to the east, and was first characterized in [1]. High-resolution RMI images [3] allow us to characterize a sedimentary succession made of rocks whose texture ranges from coarse sandstones to (boulder) conglomerates, which is common for deltaic systems. A closer observation of the sedimentary architecture was possible using a 3D DOM made from RMI images [2] (Fig. 3). On this model, we were able to precisely delimits the different bottomsets, foresets and topsets (Fig. 3a), but also to provide measurements of the individual bed thicknesses within each interval with an average of 15 cm, 17 cm and 19 cm for bottomsets, foresets and topsets, respectively. After close observation, it appears that the topsets of Unit 2 also show that at least three sets of oblique stratifications do not follow the same transport direction than the other beds, evidencing a transport clearly toward the east (green lines in Fig. 3b). Also, individual beds exhibit a reduced thickness with an average of 13.5 cm per bed (Fig. 3b). While the overall unit 2 follows a usual stacking pattern for the deposition of a prograding delta, it appears that local and recurring variations in the energy and direction of transport occurs during the late-stages of the delta’s deposition, probably following onset of meandering beds or varying direction braided bars, an observation not dissimilar to the “curvilinear unit” observed on the main delta front at equivalent elevations [4]. Finally, large-scale boulders are observed to irregularly and unconformably overlie both Delta Units 1 and 2 (Fig. 4) on top of the butte. These clasts have been measured on top of Unit 2 have an average long-axis size of ~52 cm, and range from 22 to 104 cm (Fig. 4). These poorly sorted and angular clasts are part of a clast-supported unit that seem to have deposited episodically a certain amount of time after the deposition of the main delta. This implies a strong decoupling between both settings, implying a complex history of the area, whose timely relations are yet to be ascertained. While the exploration of the main delta of Jezero crater is just beginning, the characterization of the Kodiak butte, a remote distal remnant of the past deltaic fan, is already a “gold mine” of geologic information about the aqueous past of this area. The two different episodes in the delta’s history, represented by Delta Units 1 and 2, their inner variations, but also the presence of the later boulder conglomerate unit, are informing us about the late-stage evolution of the hydrological history of the Jezero crater. This is notably important since we are observing the foresets/topsets transition to occur at ~-2490 m in elevation, that is about 100 m lower than the modeled lake level from the craters’ outlet valley [1]. Following work to precisely characterize Delta Unit 1 and the (co-)relations to the main delta units [5, 6] will therefore be paramount in assessing the paleoenvironmental evolution of the basin, its fluvial activity, and its link to the regional to global climate of ancient Mars. References: [1] Mangold et al., 2021, Science, 374, 6568. [2] Caravaca et al., 2022, LPSC, Abstract #1189. [3] Gasnault et al., 2021, LPSC¸ Abstract #2248. [4] Stack et al., 2020, Space Science Reviews, 216, 127. [5] Mangold et al., 2022, LPSC, Abstract #1814. [6] Gupta et al., 2022, LPSC, Abstract #2295.

The stratigraphy preserved within Aeolis Mons (Mount Sharp) in Gale crater (Mars) shows a major transition from mudstone-rich strata (with subordinate sandstones) recording deposition in lacustrine to fluvial settings into a major sulphate-bearing unit (the Layered Sulphate-bearing unit (LSu)) [1, 2]. This transition is interpreted to represent a major environmental change from wetter conditions toward a more arid palaeoclimate on early Mars. A stratigraphic section over this transition constructed along Curiosity’s traverse shows a vertical change from mudstones with interstratified sandstones of the Glasgow and Mercou members of the Carolyn Shoemaker formation into strata of the Pontours member which have a strong diagenetic overprint, and thence into large-scale cross-stratified sandstones of the Mirador formation that are interpreted to be the deposits of large, migrating aeolian dunes. The lower section of the LSu is dominated by stacked, cross-bedded facies with variable diagenetic overprint, that likely records a purely dry aeolian dune environment [3]. However, higher up in the studied section, approximately 80 m above the base of the Mirador formation, there is a transition into a succession still dominated by large-scale cross-beds but with interstratified lenses of a different sandstone facies. The presence of these lenses within large-scale cross bedded rocks is denoted by a transition to the Contigo member of the Mirador formation. Whilst a number of lenses are visible in the stratigraphy of the Contigo member in cliffs along Curiosity’s traverse, the Mars Science Laboratory science team selected one lens, informally named The Prow to investigate in detail. Here, we describe the sedimentology of The Prow at a range of scales using Navcam, Mastcam, ChemCam Remote Micro-Imager(RMI), and Mars Hand Lens Imager (MAHLI) images with a focus on characterizing sedimentary structures, their depositional process interpretation and comparison to Earth analogs. The 3D geometries of The Prow’s sedimentary structures are analysed by [4]. The Prow was investigated during sols 3349 and 3379 in early 2022 and had been identified as a target of interest from long distance observations suggesting that it formed constrasting facies to surrounding rocks. The Prow is an ~18-m-long, ~0.5-1-m-thick lenticular sedimentary body that is interbedded with large-scale cross-stratified facies interpreted to be aeolian dune deposits. The nature of the lower contact of The Prow is unclear. The lens pinches out to the south. The Prow shows a range of sedimentary structures suggestive of deposition under predominantly aqueous conditions. These structures differ from structures in surrounding bedrock indicating contrasting environmental conditions. The lowermost part of The Prow section appears to comprise decimetre-scale cross-beds indicative of deposition from subaqueous dune migration. The scale of these cross-beds is quite different from the large metres-scale trough cross-beds in rocks surrounding the lenses. The upper sections of The Prow are dominated by cm-scale ripple structures well observed in cross-section. In particular, lenticular and flaser geometries are observed. Lenticular ripple forms with convex upper surfaces are common with concave lower surfaces where they overlie underlying ripple forms. The ripple forms occur vertically stacked and laterally offset. The individual lenses are commonly interconnected forming complex interwoven structures. The crests generally show rounded symmetric profiles. Locally, symmetric vertical accretion over ripple crests is observed implying rapid sediment aggradation. Many ripple forms do not appear to show internal lamination, although this may be due to a lack of grain size variation. In a few examples where internal lamination is observed, preserved foresets are suggestive of unidirectional flow. RMI and MAHLI images reveal that ripple forms appear to have a finer-grained drape overlying ripple crests and extending into ripple troughs. MAHLI data confirm initial ChemCam observations and show that ripple cores comprise a sandstone and draping laminations are finer grained and likely below MAHLI-resolution (~60 microns). The drapes are provisionally interpreted as mud drapes formed from suspension fallout onto ripple topography during low energy quiescent episodes. The overall sedimentary geometry resembles flaser- to lenticular bedding common in Earth examples. The symmetric form of many of the ripple structures with preservation of form sets is suggestive of formation by oscillatory flow by wave action. Locally, there is evidence of asymmetric accretion which is likely indicative of combined flow ripples. The presence of drapes of finer-grained material superimposed on coarser-grained ripple forms is interpreted to record episodes of higher-energy sand transport separated by recurrent intervals of low-energy conditions during which sand grains could not be mobilised. Wave and current activity caused bedload transport of sand constructing symmetric and asymmetric ripples. Between these episodes, there were quiescent periods where active flow ceased and finer-than-sand grains deposited out of suspension onto temporarily fossilised ripple forms. The preservation of stacked well-preserved ripple forms with crests intact suggests conditions of rapid deposition. Locally, planar laminated beds with laterally continuous laminae are present; these maybe interpreted as either wind-ripple laminations formed by aeolian transport or as upper flow regime plane beds. The presence of mudstone-draped wave and current ripple forms in the upper section of The Prow is strongly indicative of deposition from aqueous flows and moreover suggests the existence of a likely aerially small, shallow standing body of water in which the sediments were deposited. We compare the observed structures to forms observed in 1 Ga lake deposits from the Diabaig Formation of the Torridon Group (NW Scotland). We tentatively infer that The Prow and by inference the other lenses observed in the Contigo member may record the episodic interdune or scour-fill presence of transient small standing bodies of water in an otherwise dominantly dry aeolian dune-dominated environment. The vertical transition from the underlying Dunnidear and Port Logan members of the Mirador formation that are dominated purely by large-scale trough cross bedding indicative of dry aeolian conditions indicates a change to a more mixed environmental setting with episodic fluvial/lacustrine activity perhaps from transient snow-melt or precipitation events occurring in otherwise arid conditions. Lenses such as The Prow demonstrate fluvio-lacustrine intervals punctuated dominant aeolian environment in the layered sulphate-bearing unit. References: [1] Milliken et al., 2010, Geophys. Res. Lett. 37, L04201; [2] Rapin et al., 2021, Geology 49; [3] Rapin et al., 2022, EPSC, this meeting; [4] Caravaca et al., 2022, EPSC, this meeting.

On February 18, 2021, NASA’s Mars 2020 Perseverance rover landed successfully in Jezero crater. Several geological and compositional units were previously identified from orbital data analysis : a dark pyroxene-bearing floor unit; an olivine-bearing unit exposed in erosional windows and partially altered into phyllosilicates and carbonates ; a deltaic complex and its possible erosional remnants and a marginal carbonate-bearing unit. As of Sol 300 (December 2021), the rover has visited two geological units in situ: the dark pyroxene-bearing floor unit and the olivine-bearing floor unit. Others investigations of geological units of interest have been carried out using long distance (up to several kilometers) observations.The SuperCam instrument contains a suite of techniques including passive spectroscopy in the 0.40-0.85 (VIS) and 1.3-2.6 microns (IR) wavelength ranges, and a color camera (RMI- Remote Micro-Imager) providing high resolution context images. Since the landing, SuperCam has acquired thousands of VISIR spectra of nearby rocks (including both natural and abraded surfaces), as well as hundreds of spectra of distant targets (from 10s of m to 20 km). The VISIR field of view of each individual spectrum ranges from a few mm for the rock of the workspace to 20 m to 20 km. The aim of this contribution is to summarize the main results of VISIR spectra up to Sol 300.The two geological units investigated in situ have distinct spectra. The crater floor rough unit (Cf-fr) has a pervasive 1.9 µm absorption indicative of hydration. Additional absorption at 2.28 µm indicate the presence of iron-rich phyllosilicates. Correlations between 1.9 µm and 2.4 µm absorption bands or between 2.1 µm and 2.4 µm bands suggest the presence of both poly and monohydrated sulfates. Spectra similar to oxy-hydroxides have also been observed in some rocks. Unmixing methods such as factor analyses highlight a high calcium pyroxene component. To sum up, the Cf-fr is an altered pyroxene rich unit. The second unit investigated in situ is a region called Seitah, which is dominantly olivine-rich from orbital analyses. Supercam VISIR data confirm the strong signature of olivine of the unit and display a complex suite of absorptions in the 2.3 µm - 2.4 µm region suggesting the presence of iron and magnesium phyllosilicates and/or carbonates. The alteration signature seems to be associated with olivine grains. Distant observations were acquired on the western delta front, several remote mesas and hills, on Jezero floor unit (the unit on which Perseverance landed on and investigated in situ), on Seitah before being visited by the rover, and on even more distant targets such as the crater rim or the marginal carbonate-bearing unit. The observed spectral signatures form different clusters depending on the type of target, highlighting the spectral diversity of Jezero geological units. Remarkably, the long distance observations of Seitah region are in perfect agreement with the in situ measurements confirming the relevance of long distance observations to assess the geological/mineralogical context of Perseverance’s future traverses.

Phosphorus was essential to the development of life on Earth because it enters into the composition of molecules important for biology. Since the development of organisms is often limited by phosphorus supply, secondary phosphate facies are often controlled by biological activity, especially in lacustrine and marine environments. Understanding the formation of phosphate minerals on Mars is therefore interesting not only from an astrobiological standpoint, but also to understand the phosphorus cycle in a presumably abiotic world. Here, we provide an overview of the different secondary P-rich facies that have been observed by the ChemCam instrument. Since 2012, Curiosity has been exploring geological records of a paleo-lacustrine environment in Gale crater. After encountering fluvio-deltaic and lacustrine deposits in the lowermost unit, Bradbury, it explored ~300m of stratigraphy through the Murray formation, composed predominantly of laminated clay-rich mudstones and fine-grained sandstones deposited in an extended lacustrine environment. While crossing the Sutton Island member of this formation (an heterolithic unit composed of mudstones and sandstones), a series of subhorizontal dark laminae enriched in Fe and P were found, progressively giving way to mm-size dark nodules enriched in Mn, Mg and P in the overlying Blunts Point member, growing in size with elevation [1], and to Mn-rich sandstones [1,2,3]. These laminae and nodules were interpreted as syndepositional or early diagenetic features formed in a shallow lake or lake margin environment [1,2,3]. An initial interpretation of their mineralogy, based on chemical measurements, suggested they could be hydrous Fe- and Mn-oxides formed under oxidizing conditions (with Eh increasing along the stratigraphy) at the water-sediment interface, having sorbed (MgHPO4) complexes [1], with nodules’ growth possibly controlled by reworking and winnowing. Dark nodules enriched in (Fe,Mg,P) were also observed in Ca-sulfate-filled fractures across all these units [1]. These dark features suddenly disappeared when the rover reached the Vera Rubin ridge, where only isolated and detached nodules enriched in (Mn,Fe,P), probably eroded from overlying strata, and dark-toned rock patina enriched in (Fe,P) were observed. None of these facies were then observed during the first ~500 Sols of the traverse through the Glen Torridon region, including the base of an unconformity with an overlying Aeolian sandstone unit. In the Groken area of the Glen Torridon region, dark mm-sized nodules arranged in thin layers were again discovered. A rock sample was analyzed by X-ray diffraction by CheMin, which did not detect any crystalline forms of oxides nor phosphates [4]. Meanwhile, the phosphorus and manganese abundances measured by ChemCam have been quantified, which led us to revise prior interpretations. The constant P/Mn ratio in the Groken nodules and their P abundance (too large to be explained by P-sorption to oxides) suggest they are composed of nano-crystalline or amorphous hydrous (Mn,Mg)-phosphates. Previous occurrences are now interpreted as hydrous (Fe,Mn,Mg)-phosphates with varying (Fe,Mn,Mg) proportions. Several formation scenarios are being explored by geochemical modeling [5]. [1] Meslin et al., LPSC, 2018[2] Gasda et al., LPSC, 2018[3] Lanza et al., LPSC, 2018[4] Treiman et al., LPSC, 2022[5] Loche et al., LPSC, 2022

International audience; Orbital and rover observations of relictgeomorphic features and stratigraphic architectures indicate Mars once had a warmer, wetter climate. Constraining the character, relative timing and persistence of ancient aqueous activity on Mars is possible through detailed interrogation of the stratal geometry of aqueously deposited sedimentary bodies. Such analyses inform interpretations of Martian climate evolution, potential habitability, and search strategies for rocks that might contain potential biosignatures. A prominent sedimentary fan deposit at the westernmargin of Jezero crater has been inferred to be a river delta that built into an ancient lake basin during the Late Noachian-Early Hesperian epochs on Mars (~3.6-3.8 Ga) [1, 2, 3]. The Perseverance rover landed on 18 February 2021 ~2.2 km from the western fan. During the early phase of mission investigations, highresolution images obtained from the Mastcam-Z camera and from the Remote Micro-Imager of the SuperCaminstrument provided the first ground-based observations of the western fan and an associated remnant outcrop, named Kodiak. Here, we report its sedimentology, which provide new constraints on the nature of the fan deposits, and their paleoenvironmental implications (4).

International audience; Since its landing in 2012, the Curiosity rover has been exploring geological records of a paleolacustrine environment in Gale crater. It started with the fluvio-deltaic and lacustrine deposits in the lowermost Bradbury Group, followed by 300 m of stratigraphy through the Murray formation (from the Pahrump Hills to the Jura member) dominated by mudstones and occasionally heterolithic mudstones, siltstones and sandstones. Along this traverse, it also crossed the unconformity with the overlying Stimson formation, dominated by aeolian sandstones, and the Vera Rubin Ridge, an erosion-resistant section of the Murray fm., which has undergone extensive diagenesis [1]. From Sol 2300 to 3072 (Jan. 2019 to Jan. 2021), Curiosity has explored the Glen Torridon region, previously named "Claybearing unit" because of the orbital signatures of clays detected in this area. Since Sol 3100 (Mont Mercou), the rover entered the basal Layered Sulfate unit (also named after orbital observations) with the objective of documenting a possible major change in Mars climate history. Evaporitic salts could represent a geochemical marker of this transition. Here, we provide an overview of previous halite detections by ChemCam [2, 3] and report on new detections made in the sulfate-bearing unit. Data and Method: This study covers data acquired by the ChemCam instrument over the first 3300 sols of the mission and corresponding to ~27800 LIBS analysis points. The detection of halite is made possible by measuring the chlorine emission line at 837.8 nm. Comparing the chlorine peak area to the Na abundance reveals the presence of a group of points showing a strong linear correlation between the two elements (Fig. 1).

International audience; The Perseverance rover landed on the floor of Jezero crater on 18 February 2021. The landing site, named “Octavia E. Butler” is located ~2.2 km from the SE-facing erosional scarp of the western fan deposits, which are of strong interest for the mission [1-2]. Images obtained using the Mastcam-Z camera and the Remote Micro-Imager (RMI) of the SuperCam instrument provided the first Mars ground-based observations of this western fan (Fig. 1). At the distance images were taken, the RMI images offer a pixel resolution of 2.2 cm, thus enabling identification of objects of typically 7-8 cm (3-4 pixels). Observations of the residual butte Kodiak confirmed the presence of a lake within Jezero crater, but also showed that the lake deduced from the deltaic architecture at Kodiak had a level ~100 m lower than expected (-2495/-2500 m), and was thus a closed system for a significant period [3]. In addition, the coarser deposits (boulder conglomerates and pebbly sandstones) observed near the top of all of the scarps are typical of fluvial floods with high energy, reflecting a change in hydrology of the fluvial system. Here, we focus on the hydrological characteristics of fluvial deposits observed within the scarps of the delta, both as topsets and as boulder conglomerates.

International audience; During their third Extra-Vehicular Activity, Apollo 17 astronauts had the opportunity to photo-document with their Hasselblad cameras a collection of five large boulder fragments and regolith, lying at the base of a long trail descending from the North Massif [1] (Fig. 1). We recombined these original photographs using photogrammetry techniques to reproduce 3D digital models of the boulders [2]. These digital copies of the boulders can then be reinvestigated using either a web based platform (e.g., Sketchfab), or with a Virtual Reality headset on a dedicated SteamVR scene. Whereas the original images were not native stereo pairs, series of stereoscopic pairs can also easily be numerically recomputed from the 3D model in order to provide immersive views using a more conventional stereoscope system, for outreach purposes.

International audience; Glen Torridon is a topographic trough located on the slope of Aeolis Mons, Gale crater, Mars. It corresponds to what was previously referred to as the “clay-bearing unit”, due to the relatively strong spectral signatures of clay minerals (mainly ferric smectites) detected from orbit. Starting in January 2019, the Curiosity rover explored Glen Torridon for more than 700 sols (Martian days). The objectives of this campaign included acquiring a detailed understanding of the geologic context in which the clay minerals were formed, and determining the intensity of aqueous alteration experienced by the sediments. Here, we present the major-element geochemistry of the bedrock as analyzed by the ChemCam instrument. Our results reveal that the two main types of bedrock exposures identified in the lower part of Glen Torridon are associated with distinct chemical compositions (K-rich and Mg-rich), for which we are able to propose mineralogical interpretations. Moreover, the topmost stratigraphic member exposed in the region displays a stronger diagenetic overprint, especially at two locations close to the unconformable contact with the overlying Stimson formation, where the bedrock composition significantly deviates from the rest of Glen Torridon. Overall, the values of the Chemical Index of Alteration determined with ChemCam are elevated by Martian standards, suggesting the formation of clay minerals through open-system weathering. However, there is no indication that the alteration was stronger than in some terrains previously visited by Curiosity, which in turn implies that the enhanced orbital signatures are mostly controlled by non-compositional factors.

Introduction In January 2019, the Mars Science Laboratory (MSL) rover Curiosity started exploring the Glen Torridon (GT) region of Gale crater, which corresponds to the topographic trough between the Vera Rubin ridge and the Greenheugh pediment (Fig. 1). From orbit, this region stands out due to the rela­tively strong near-infrared signatures of clay minerals [1,2]. The in-situ data collected so far by Curiosity have allowed the MSL team to confirm and quantify the presence of these clay minerals [3], to characterize their organic content [4], and to document in detail their geochemical and sedimentological settings [5]. In particular, the bedrock chemistry measured by ChemCam shows elevated values of the Chemical Index of Alteration (CIA) throughout most of Glen Torridon [6,7], which indicates an open-system type of alteration [8]. In addition, the ChemCam observations suggest the presence of illite in the fine-grained rocks [9] and reveal a possible relationship between grain size and geochemical variations [10]. Finally, they show that the light-toned rocks located just below the uncon­formity at the base of the Greenheugh pediment (Fig. 1) are associated with “anoma­lous” bedrock compositions that may be related to a late-stage diagenetic event at Gale [7]. Here, we report the findings of the ChemCam instrument along a ~2-km eastward traverse within the upper member – named Glasgow – of the Glen Torridon region (Fig. 1). This traverse allowed Curiosity to investigate the lateral variability of this member, while also getting gradually closer to the transition into the overlying sulfate-bearing unit [11]. Dataset ChemCam measures the chemical composition of targeted rocks and soils within a few meters of the rover using laser-induced breakdown spectro­scopy (LIBS). Quantification of eight major rock-forming oxides is performed routinely [12]. Each Chem­Cam analysis consists of a raster of several points a few millimeters apart from each other, and each point itself consists of a series of laser shots (typically 30). For bedrock targets, this approach allows removal of unwanted contributions from Ca-sulfate veins or soil material by discarding the corresponding points [e.g., 8]. On sol 3007, ChemCam experienced a technical issue, which required halting the use of the laser during the time of the investigation, while imaging and passive spectroscopy activities continued. LIBS analyses on Mars targets resumed on sol 3107, in the Mont Mercou area (Fig. 1), ~600 m to the east and ~19 m higher in elevation. In addition, data acquired between sols 2816 and 2956 are not used here, since they correspond to a downsection excursion into the underlying Knockfarril Hill member [13]. Results Variations in MgO, K2O and FeOT abun­dances along the rover path within the Glasgow member are shown in Figures 2, 3 and 4 (respectively). The bedrock composition is overall homogeneous, although small variations are observed for some oxides. In particular, the mean MgO abundance was well below 5 wt% in the western part of the traverse, but reached nearly 6 wt% after the downsection excursion (Fig. 2). This increase in MgO is accompanied by slightly lower Al2O3 abundances (not shown here). In contrast, the K2O content does not show a clear change after the excursion (Fig. 3); however, it decreases slightly during the exploration of an area with rougher terrain (previously mapped as “fIU rubbly” [14]), between sols 2973 and 3000. Regarding FeOT, large variations have been observed at small scale (i.e., within a given LIBS raster) in a group of targets characterized by the presence of dark nodules, likely of diagenetic origin [15,16]. These nodules have high FeOT (up to ~50 wt%), whereas the points in between the nodules show low FeOT (down to ~12.5 wt%). However, at the scale of the whole Glasgow member, the mean FeOT content is quite stable, with only a subtle increase in the eastern part of the traverse (Fig. 4). As mentioned above, the most recent data (last bin in Fig. 2-4) were acquired after a gap of ~600 m laterally and ~19 m vertically. Despite this gap, the bedrock compositions appear remarkably similar to those measured earlier in the Glasgow member, especially after the downsection excursion. This suggests that no major change of environment occurred during the time when LIBS was unavailable. Discussion and conclusion Curiosity’s eastward traverse within the Glasgow member is a rare opportunity to investigate the lateral variability of Gale sedimentary strata at the kilometer scale. The compositions appear overall homogeneous, but some variations are observed. As previously seen in Glen Torridon [6,7,10], Mg and K are the two most varying elements; however, their variations are not always well correlated, as illustrated by the trends observed after the downsection excursion (Fig. 2-3). In addition, while FeOT displays significant variations within some LIBS rasters due to the presence of dark nodules in the bedrock, it is stable at the scale of the whole Glasgow member, which suggests that diagenetic remobilization of iron occurred at small scale only. Finally, the latest data acquired in the Mont Mercou area show that the bedrock compositions are still remarkably similar to those measured ~2 km to the west, when Curiosity first encountered the Glasgow member. As the rover continues to progress uphill, ChemCam will continue surveying the bedrock in search of the first chemical indications of the clay-to-sulfate transition. References: [1] Milliken et al. (2010) GRL, 37. [2] Fraeman et al. (2016) JGR-Planets, 121. [3] Thorpe et al. (2021) LPSC, abstract #1519. [4] Millan et al. (2021) LPSC, abstract #2039. [5] Fedo et al. (2020) LPSC, abstract #2345. [6] Dehouck et al. (2020) LPSC, abstract #2770. [7] Dehouck et al. (2020) AGU Fall Meeting, abstract #P070-06. [8] Mangold et al. (2019) Icarus, 321. [9] Cousin et al. (2021) LPSC, abstract #2127. [10] Caravaca et al. (2021) LPSC, abstract #1455. [11] Rapin et al. (2021) Geology, 49. [12] Clegg et al. (2017) Spectrochim. Acta B, 129. [13] Dehouck et al. (2021) LPSC, abstract #1858. [14] Hughes et al. (2021) LPSC, abstract #1586. [15] David et al. (2021) LPSC, abstract #1433. [16] Gasda et al. (2021) LPSC, abstract #1271.

Gale crater on Mars records a large section of sedimentary rocks, mainly represented by the 5-km-thick sequence of Mount Sharp (Aeolis Mons). The lower part of this sequence has been explored by the Curiosity rover of the Mars Science Laboratory (MSL) mission, revealing lacustrine to fluvial depositional sequences [e.g., 1] bearing clay minerals [2]. Orbital observations highlighted the presence of clay minerals at the base of Mt Sharp but also hint at a major wet to dry environmental change 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 record coincides with a major change of depositional environment followed by alternation of wetter and drier conditions rather than a monotonous aridification during the Hesperian epoch [5]. Before Curiosity reached this part of Gale crater, those observations were supported using long-distance imaging capabilities of the Remote Micro-Imager (RMI) sub-system of the ChemCam instrument [6]. With a focal length of 700 mm, the RMI telescope complements the color Mastcam imagers with higher spatial resolution views of sedimentary structures and textures of rocks outcropping several hundred meters up to a few kilometers away from the rover (a ~60 km-record observation having recently been achieved, [7]). This capacity is therefore used by the MSL team both to plan future guidance of the rover and to observe geologic features from a distance. These long-distance observations pointed at the sulfate-bearing unit reveal the presence of sub-metric-scale cross-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 away using imagers onboard the rover, Mastcam and RMI), the resulting images lacks depth due to the distance. Yet, such 3D information can be critical in characterizing and understanding the sedimentary processes behind the setting of these structures. To improve our observations, we are conducting an imaging experiment to reconstruct the 3D shape of the sulfate-bearing unit outcrops with Structure-from-Motion photogrammetry using ChemCam’s RMI frames. This method is usually performed on close-range geologic features observed with other imagers onboard the rover (MAHLI, Mastcam, Navcam, [8]), but such an approach had never been applied to long-distance RMI frames. Here, we apply photogrammetric treatment to specific sets of repeated long-distance observations on the sulfate-bearing unit. To cope with the high distance of the target, we use a several-hundred meters “virtual baseline” represented by successive positions of 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. This mosaic illustrates an outcrop of the sulfate-bearing unit situated ~650 meters away from the rover at 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). By combining the individual frames of these two mosaics in the photogrammetric chain, we were able to reconstruct the shape of the outcrop. The resulting 3D model presented in Figure 3 reveals the actual 3D shape of the imaged outcrop situated several hundred meters away from the rover, as well as displaying with improved accuracy the spatial distribution of the sedimentary and/or diagenetic structures. The use of this technique to produce long-distance 3D models will have critical implication in helping to assess and to characterize the depositional conditions related to the sulfate-bearing unit, a key objective of the Curiosity rover. The use of these models could also serve to help planning the upcoming exploration of this interval by designating high-interest targets. We also look forward to applying this method to long-distance color images obtained with the more advanced color RMI subsystem of the SuperCam instrument onboard the Perseverance rover currently operating in Jezero crater [9, 10]. References:[1] Caravaca et al., 2021 LSPC, abstract #1455; [2] Thorpe M. T. et al., 2021, LPSC, Abstract #1519; [3] Miliken et al., 2010, Geophys. Res. Lett. 37, L04201; [4] Fraeman A. A. et al., 2016, J. Geophys. Res. Planets 121, 1713–1736; [5] Rapin et al., 2021, Geology 49; [6] Le Mouélic et al., 2015, Icarus 249, 93-107; [7] Le Mouélic et al., 2021, LPSC Abstract #1408; [8] Caravaca et al., 2020, Planet. Space Science 182, 104808; [9] Gasnault et al., 2021, LPSC Abstract #2248; [10] Gasnault et al., 2021, EGU Abstract #EGU21-16461.

Grain size in martian sedimentary rocks can be constrained using point-to-point chemical variabilities in Laser Induced Breakdown Spectroscopy (LIBS) data from the ChemCam instrument on the Mars Science Laboratory (MSL) Curiosity rover. The diameter of each point ablated by the ChemCam laser is in the range of medium to coarse sand in size. Thus, rocks with grains significantly smaller than the laser spot size produce bulk rock compositions at each LIBS point and low point-to-point chemical variability among LIBS points. In contrast, analyses of rocks with grains about the size of the spot or larger contain contributions from individual grains at each point and often have high point-to-point chemical variability. The Gini index, a statistical parameter, was used to calculate the point-to-point chemical variability in major-element oxide compositions derived from the ChemCam LIBS data. First, the total range of each LIBS major-element oxide composition was normalized from 0 to 1 across all LIBS observations. Then the Gini index was calculated for each oxide in each LIBS observation. Finally, the Gini indices of each oxide were averaged to derive a Gini index mean score, G MEAN , for each LIBS observation. A correlation between G MEAN and grain size was validated using sedimentary rocks of various grain sizes from the Yellowknife Bay formation and the Pahrump Hills member of the Murray formation in Gale crater. Overall, finer-grained rocks had smaller G MEAN than coarser-grained rocks. To calibrate G MEAN to grain size, grain size estimates based on visual assessment of high-resolution images were compared to G MEAN values for the same targets to create a calibrated scale. This calibrated scale was used to infer the grain size of rocks with unknown grain size. Overall, the grain sizes predicted for rocks with unknown grain size overlapped with those of known grain size from the same units and/or bedrock targets. The grain sizes inferred using the G MEAN based on ChemCam LIBS data are complimentary to those determined from images and both techniques can be used to improve interpretations of the depositional environments of rocks analyzed by Curiosity and future Mars missions with LIBS, such as the Mars 2020 rover.

Landslides are common features on the surface of Mars. They have morphologies that resemble debris slides, mudflows [1], or giant rock avalanches [e.g., 2] on Earth. They can mobilise large quantities of material up to 1012 m3 and spread over areas of up to 109 m2 [e.g., 3].The topography before the landslide event occurred is required to both estimate the volume of mobilised material and quantify the distribution and thickness of the deposit. The mass distribution of the deposit can also be used to compare with 3D flow simulations of landslides [e.g. 1, 3]. However, on Mars there are no landslides that have known topographic data before the event occurred, hence we have to rely on topographic reconstruction.This type of reconstruction, which we have already carried out using HiRISE (High Resolution Imaging Science Experiment) Digital Elevation Models (DEM) with 1-2 m vertical resolution [e.g., 1], has never been undertaken using DEMs with 4-5 m vertical resolution derived from CaSSIS (Colour and Stereo Surface Imaging System) stereo pairs [4]. CaSSIS uses a 180° camera rotation to capture stereo images of a given site in a single pass. DEMs are then generated using 3DPD (three Dimensional reconstruction of Planetary Data) software [5].Our aim is to test whether a landslide reconstruction can be carried out with a CaSSIS DEM. For our purpose we use a 6 km long landslide in Baetis Chaos region, Mars.Our reconstruction consists of three main steps: 1) We first calculate contour lines. 2) Reconstructed contour lines are then drawn by connecting contour lines on either side of the boundary taking into account the overall topography outside the landslide. 3) Then, the reconstructed contour lines are converted into points at intervals equal to the spatial resolution of the DEM. These points are then interpolated using a natural neighbour algorithm to calculate a new DEM without the landslide. We were able to estimate that the landslide in Baetis Chaos has a volume of 108 m3 and the deposit has a maximum thickness of 200 m using CaSSIS data.Our successful reconstruction using a CaSSIS DEM increases the potential coverage of high-resolution stereo-topographic data beyond those already available with CTX and/or HiRISE. The resolution CaSSIS DEMs fills a gap in the topographic data currently available for studying landslides. Landslides > 15 km long can be studied with MOLA or HRSC data, and landslides < 5 km long can be studied using HiRISE data. Now, landslides and other landforms 5-15 km can be studied using CaSSIS data with equivalent quality to CTX stereo-topography.Acknowledgement: CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova (ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.References: [1] A. Guimpier et al. (In review) PSS. [2] G. Magnarini et al. (2019) Nature Communications. [3] G.B. Crosta et al. (2018) ESS, 5, 89–119. [4] A. Lucas et al. (2014) Nature Communications. [5] E. Simioni et al. (In press) PSS.

Mars’ transition from an early “warm and wet” to a “cold and dry” environment left fingerprints on the geological record of fluvial activity on Mars. The morphological and mineralogical observations of aqueous activity provided varying constraints on the condition and duration of liquid water on the Martian surface. In this study, we surveyed the mineralogy of Martian alluvial fans and deltas and investigated the hydrated silica-bearing deposits associated with some of these landforms. Using CRISM data, we identified 35 locations across Mars with hydrated silica in proximity to fans/deltas, where the spectral characteristics are consistent with immature or dehydrated opal-A. In a few stepped fans/deltas, we find hydrated silica occurs within the bulk fan deposits and form sedimentary layers correlated with elevation. Meanwhile, in the older fans/deltas, silica mostly occurs at distal locations, and the relation to primary sedimentary deposits is more complex. We propose that the hydrated silica-bearing deposits in stepped fans/deltas likely formed authigenically from Martian surface waters, mainly during the Late Hesperian and Early Amazonian. These silica-bearing deposits could be a tracer for the temperature or duration of water involved in the formation of these deposits, given more precise and detailed observations of the sedimentary context, accessory minerals, the concentration of hydrated silica, and sediment-to-water ratio. Therefore, we consider that silica-bearing deposits should be among the most critical samples to investigate for future Mars missions, which are accessible in the landing sites of Mars 2020 and ExoMars 2022 missions.

International audience; Virtual Reality (VR) and Augmented Reality (AR) coupled with 3D terrain reconstructions are increasingly used for science, education and out-reach applications. These techniques are becom-ing more widespread thanks to the release since 2016 of reliable, versatile and cost-effective hardware solutions accessible to the general public. In the field of planetol-ogy, VR and AR theoretically allow the possibility to simulate field trips to remote places that are otherwise inaccessible to humans. Using high-resolution imaging, coupled with spectral or morphological data gathered by robotic explorers (orbiters, landers, rovers), we can cre-ate integrated virtual environments that accurately rep-resent the surface of planetary bodies and allow visual-ization and characterization of different datasets. These virtual environments provide the possibility to navigate on a global scale using orbital data, and move down to the surface when in situ data are available to explore and analyze local outcrops. This is particularly useful in the cases of the Moon and Mars, where both extensive or-bital and in situ data are available.

International audience; In July 2020, the Curiosity rover encountered a region of bedrock that contained an abundance of layered nodular features and highly unusual Mn- and sometimes P-rich chemistries (Fig.1a) in Glen Torridon (GT), a phyllosilicate-rich mudstone to sandstone deposit [1]. This sampling location was originally targeted at a distance as a site for the Sample Analysis at Mars (SAM) instrument to perform one of its two tetramethylammonium hydroxide (TMAH) wet chemistry experiments [2] in the hopes that the new location would provide similar rocks to the previously analyzed clay-rich Glen Etive targets at approximately the same elevation [3].

International audience; Since Jan. 2019 (~sol 2300), the Mars Science Laboratory rover Curiosity has been ex-ploring the Glen Torridon (GT) region of Gale Crater, seeking to examine clay-bearing strata initially detected using orbiter data [1]. The presence of hydrated clay minerals has major implications for understanding the wet early Mars. The sedimentary record of the GT re-gion is comprised of mudstones interbedded with very fine- to medium-grained sandstones of the Jura and Knockfarril Hill (KHm) members of the Murray Fm., respectively [2]. However, their varying sedimentary, stratigraphic, and geochemical characteristics suggest potential changes in the depositional settings that could have favored enhanced accumulation and/or in situ for-mation of secondary clay minerals [e.g., 3]. Here, we examine the sedimentary and geochemical records of four major outcrops (Woodland Bay, Teal Ridge, Strathdon area and Glen Etive) in the northern part of GT, an area where exceptionally developed outcrops are present.

International audience; Gale crater preserves a 5-km-thick sequence of stratified rocks, the lower-most section of which exhibits orbital spectra signatures of clay miner-als transitioning up to sulfates over several hundred me-ters of stratigraphy [1,2]. Understanding the reason for this wet-to-dry change recorded in the mineralogical signature is one of the primary objectives for the Curi-osity rover. The rover is currently positioned at the base of the Layered Sulfate unit (LSu) exposed over a thou-sand meters of elevation, which is characterized from orbit by its general-layered texture and spectral signa-tures of monohydrated and polyhydrated Mg-sulfates [1–3]. Most of the LSu is composed of subparallel beds that vary in albedo, texture, and thickness [4]. The lower ~150 m interval of the LSu is topped by a distinctive layer referred to as the "marker bed" (Figure 1).Here we reconcile orbital data with new in situ anal-yses using MastCam and the ChemCam instrument’s Remote Micro-Imager (RMI) to provide an updated documentation of the LSu stratal components at large outcrop scales and at the highest available resolution. We then propose provisional models for the deposi-tional systems and their evolution in the sulfate unit, hy-pothesized to reflect overall a history of the diminishing availability of liquid water on Mars.

Antoniadi basin is a 330 km diameter Noachian basin localized in the East of Arabia Terra that contains a network of ridges with a tree-like organization. Branched ridges, such as these can form by a variety of processes including the inversion of fluvial deposits, thus potentially highlighting aqueous processes of interest for understanding Mars’ climate evolution. Here, we test this hypothesis by analyzing in details data from Colour and Stereo Surface Imaging System (CaSSIS), High Resolution Imaging Science Experiment (HiRISE) and High Resolution Stereo Camera (HRSC).Branched ridges are up to 10 km long and from 10 to 200 m wide without obvious organization in width. The branched ridges texture is rubbly with the occurrence of blocks up to ~1 m in size and a complete lack of layering. A HiRISE elevation model shows the local slope is of 0.2° toward South, and thus contrary to the apparent network organization (assuming tributary flows). There is no indication of exhumation of these ridges from layers below the current plains surface. Our observations are not consistent with the interpretation of digitate landforms such as inverted channels: (i) The rubbly texture lacking any layering at meter scale is distinct from inverted channels as observed elsewhere on Mars. (ii) Heads of presumed inverted channels display a lobate shape unlike river springs. (iii) There is no increase in width from small branches toward North as expected for channels with increasing discharge rates downstream. (iv) The slope toward South is contrary to the inferred flow direction to the North. The detailed analysis of these branched ridges shows many characteristics difficult to reconcile with inverted channels formed by fluvial channels flowing northward. Subglacial drainages are known to locally flow against topography, but they are rarely dendritic. Assuming that deposition occurred along the current slope, thus from North to South, the organization of the network requires a control by distributary channels rather than tributary ones. Distributary channels are possible for fluvial flows, but generally limited to braiding regimes or deltaic deposits, of which no further evidence is observed here. The lobate digitate shapes of the degree 1 branches are actually more in line with deposits of viscous flows, thus as terminal branches. Such an interpretation is consistent with lava or mudflows that formed along the current topography. The next step in this study will be to determine more precisely the rheology of these unusual flows.Acknowledgments: French authors are supported by the CNES. The authors wish to thank the spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA’s PRODEX. The instrument hardware development was also supported by the Italian Space Agency (ASI) (agreement no. I/018/12/0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the Univ. of Arizona (Lunar and Planet. Lab.) and NASA are gratefully acknowledged.

The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam's body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245-340 and 385-465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535-853 nm ( 105 - 7070 cm − 1 Raman shift relative to the 532 nm green laser beam) with 12 cm − 1 full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well., Proyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-R

The spectral analysis of a planetary surface is fundamental for a deeper understanding of the mineralogy and composition. In particular, the determination of spectral units is a reliable method to infer the physical and compositional properties of a surface by processing several spectral parameters simultaneously, instead of the more traditional approach of interpreting each single parameter separately. To define the spectal units, we first compute the most relevant spectral parameters, based on a preliminary detailed analysis of the spectral properties of a surface. This method could be used for different bodies and is described in [1].For this work, we selected the Apollo Basin area within South Polar Aitken [2,3], the largest and deepest impact basin on the Moon. We analyzed the M3/Chandrayaan-1 data [4] after performing the most up-to-date calibration, thermal removal and photometric correction [5,6]. Lunar spectra are characterized by two strong pyroxenes absorption bands at 1 and 2 µm. In this regard, we decided to define the Apollo Basin spectral units by using the two pyroxenes band depths, the reflectance at 540 nm (standard visible wavelength), and the spectral slope of the 1 µm (see [7]). In Apollo Basin, we found 12 different spectral units. Among these units, the most peculiar is the one linked to the basaltic smooth plains within the floor of the crater. This unit is characterized by low reflectance, deep band depths and a strongly positive spectral slopes (more red surfaces). Subsequently, an analysis of absorption band center at 1 and 2 µm and a comparison with RELAB synthetic pyroxenes [8] revealed a composition compatible with material dominated by strong pyroxene absorptions, e.g. clinopiroxenes, such as pigeonite or augite, with Low Ca and Mg, and relatively high Fe (Fs: 34-75; En: 6-23; Wo: 10-27). The rest of the units show a similar mineralogy to the orthopyroxenes, with intermediate amount of Fe and Mg.This work allows for a detailed understanding of the mineralogy of Apollo Basin, but also lays the groundwork to search for a link between spectral, and morpho-stratigraphic units [9] to reach out highly informative geological maps of the Moon. This innovative approach is one of the main goals of the H2020 no. 776276-PLANMAP project [10].Acknowledgments: This work is funded by the European Union’s Horizon 2020 research grant agreement No 776276- PLANMAP.References: [1] Zambon et al., 2020 LPSC. [2] Ohtake, M. et al., 2014, GRL. [3] Moriarty, D.P. et al., 2018, JGR. [4] Pieters et al., 2009, Current Science. [5] PLANMAP D4.3- Spectral Indices and RGB maps. [6] Besse, S. et al., 2012, Icarus. [7] PLANMAP D4.3- Spectral Indices and RGB maps. [8] http://planetary.brown.edu/relabdocs/synth_pyx/pyroxenes.html. [9] Ivanov, M.A., 2018, JGR. [10] https://www.planmap.eu/.

Kaolinite is an Al-rich phyllosilicate commonly observed on Earth as a product of the chemical weathering of aluminosilicates. It has also been detected on the martian surface by orbital remote sensing observations. While the determination of the geological processes of formation of terrestrial kaolinite (i.e., hydrothermal activity, continental surface weathering, diagenesis) involves the coupling of field observation and multiple laboratory measurements, only geomorphology and associated minerals are generally available to determine their geological origin on Mars. Kaolinite crystallinity depends on many physicochemical parameters reflecting its conditions of crystallization. To determine if the near-infrared (NIR) spectral signature of kaolinite enables estimation of its crystallinity and furthermore if this method can be used to identify the geological processes involved in kaolinite formation, we carried out an in-depth analysis of NIR spectra of reference terrestrial kaolinites that formed in various geological contexts. We calculated second and third derivatives for each spectrum to highlight subtle variations in the spectral properties of kaolinite. This allowed the identification of 27 spectral contributions for the 4500 and 7000 cm−1 Al-OH-related regions of absorption bands. The position shifts and shape variations of these spectral contributions were intimately linked to variations of crystallinity, which was qualitatively estimated using Hinckley and Liétard XRD (dis)order indices. The results obtained show that the NIR signature of kaolinite is influenced by the stacking disorder of layers that has some influence on the vibrations of the interfoliar and inner Al-OH groups. Our study also confirms that: (1) well-ordered kaolinites are not restricted to hydrothermal deposits; (2) kaolinites from a similar sedimentary or pedogenetic context often display contrasting degrees of crystalline order; and (3) poorly ordered kaolinites are more likely to have a sedimentary or pedogenetic origin. Finally, this work highlights that obtaining spectra with sufficient spectral resolution could help to estimate the crystallinity of kaolinite and, in the best cases, its geological origin, both on Earth and Mars, especially with in situ NIR measurements.

Stack, K. et al., The Mars 2020 Perseverance rover landing site is located within Jezero crater, a ∼50km diameter impact crater interpreted to be a Noachian-aged lake basin inside the western edge of the Isidis impact structure. Jezero hosts remnants of a fluvial delta, inlet and outlet valleys, and infill deposits containing diverse carbonate, mafic, and hydrated minerals. Prior to the launch of the Mars 2020 mission, members of the Science Team collaborated to produce a photogeologic map of the Perseverance landing site in Jezero crater. Mapping was performed at a 1:5000 digital map scale using a 25 cm/pixel High Resolution Imaging Science Experiment (HiRISE) orthoimage mosaic base map and a 1 m/pixel HiRISE stereo digital terrain model. Mapped bedrock and surficial units were distinguished by differences in relative brightness, tone, topography, surface texture, and apparent roughness. Mapped bedrock units are generally consistent with those identified in previously published mapping efforts, but this study’s map includes the distribution of surficial deposits and sub-units of the Jezero delta at a higher level of detail than previous studies. This study considers four possible unit correlations to explain the relative age relationships of major units within the map area. Unit correlations include previously published interpretations as well as those that consider more complex interfingering relationships and alternative relative age relationships. The photogeologic map presented here is the foundation for scientific hypothesis development and strategic planning for Perseverance’s exploration of Jezero crater., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

According to recent mineralogical study, the presence of an iron oxi-hydroxide (akaganeite) which form under specific conditions, has been detected in Robert Sharp crater, located in the equatorial region of Mars (133.59°'E, -4.12°N), implying an acidic and oxidizing environment in this region. These deposits of akaganeite might be the ultimate alteration phase of a drying lake or lagoon within Robert Sharp. Morphological and stratigraphical studies and, as well, age determination has been carried out in order to constrain the geological and hydrological history of Robert Sharp. Robert Sharp has known a varied geological history, including the formation of fretted terrains and an aerial/aeolian filling during the Hesperian epoch. The presence of valleys and fan-shaped deposits, and the detection of several aqueous minerals, in the crater suggest the presence of a fluvio-lacustrine activity phase in the crater during the last period of the Martian chronology, the Amazonian epoch. The existence of a putative paleo-lake should be short-time and estimated between 1.3 Ga and 500 Ma. Thus, this study shows that Mars has known several phases of aqueous activities well after the late Noachian/ early Hesperian period.

South Polar Aitken (SPA) is the largest and deepest basin on the Moon [1, 2], and several regions within this widespread basin have been considered as possible landing sites for present and future missions. Some of these sites are also targets of the H2020 n° 776276- PLANMAP project [3]. In this work, we focus on specific areas within SPA, Apollo basin, Lebinitz and Von Karman craters regions (see fig. 1). For our analysis, we considered the M3/Chandrayaan-1 data [4], after the application of the last calibration, thermal removal and photometric correction [5, 6]. SPA is rich in high Ca-pyroxenes, except for some central crater peaks, where low Ca-pyroxenes dominate, and no extensive olivine-rich areas are observed [1, 7, 8]. Based on the spectral characteristics on the M3 spectra, we define specific spectral parameters, such as band centers, depths, spectral slopes, including selected RGB color composite combinations [5]. These indices are the starting point for retrieving the spectral units of the regions considered. The final aim of this work is to find a link between spectral, and morpho-stratigraphic units [9] to reach out highly informative geological maps of the Moon. This innovative approach holds the efforts of different research units and is one of the main goals of the PLANMAP project. References: [1] Ohtake, M. et al., 2014, GRL. [2] Moriarty, D.P. et al., 2018, JGR. [3] https://www.planmap.eu/, [4] Pieters et al., 2009, Current Science., [5] PLANMAP D4.3- Spectral Indices and RGB maps. [6] Besse, S. et al., 2012, Icarus. [7] Dhingra, D., 2018, Geosciences. [8] Melosh, H. J., et al., 2017, Geology. [9] Ivanov, M.A., 2018, JGR. Acknowledgments: This work is funded by the European Union’s Horizon 2020 research grant agreement No 776276- PLANMAP. Figure 1: Apollo basin (top-left) and Leibnitz and Von Karman craters (bottom-left) reflectance map at 540 nm. Apollo basin (top-right) and Leibnitz and Von Karman craters (bottom-right) Clementine-like mosaic derived by M3 data (bottom-right).