Structural analysis of sulfate vein networks in Gale crater (Mars)

The Curiosity rover's campaign in the Gale crater on Mars provides a large set of close-up images of sedimentary formations outcrops displaying a variety of diagenetic features such as light-toned veins, nodules and raised ridges. Through 2D and 3D analyses of Mastcam images we herein reconstruct the vein network of a sample area and estimated the stress field. Assessment of the spatial distribution of light-toned veins shows that the basin infillings, after burial and consolidation, experienced a sub-vertical compression and lateral extension coupled with fluid overpressure and cracking. Overall, rock failure and light-toned veins formations could have been generated by an overload produced by infilling material within the basin

Processus diagénétiques sur Mars : analyse par l'instrument ChemCam à bord du rover Curiosity

L’exploration de la surface de Mars par le rover Curiosity, au niveau du cratère Gale, a permis de révéler la présence de conditions habitables par le passe, a travers l’observation de dépôts sédimentaires fluvio-lacustres attestant d'une activité hydrologique prolongée. Ces roches portent également les stigmates de l’évolution complexe des sédiments lors de la diagenèse, sous forme de veines, nodules et concrétions s'etant formes par la circulation de fluides en sub-surface. A bord du rover, la spectroscopie de plasma induit par laser (LIBS) de l’instrument ChemCam permet une mesure chimique a petite échelle, particulièrement adaptée a l'analyse de tels éléments géologiques. Cette étude démontre que les veines de Ca-sulfate, observées dans toutes les unités géologiques traversées par le rover, présentent des enrichissements ponctuels en Fe témoignant de conditions de formation oxydantes lors de la diagenèse tardive. Par ailleurs, l’une des structures sédimentaires du cratère est caractérisée par des signatures spectrales d’hématite depuis l'orbite, suggérant que sa formation est en partie liée a des processus d'oxydo-reduction, pendant et/ou après le dépôt des sédiments. A cet endroit, ChemCam a mis en évidence la mobilité du Fe lors de la diagenèse, ainsi que la formation d'oxyde de Fe en association avec les veines de Ca-sulfate. Pour conclure, ces travaux montrent l'importance des interactions fluides-roches, comme les réactions d’oxydoreduction, lors de l’enfouissement des sédiments martiens, processus devant être pris en compte pour éviter des erreurs d’interprétation sur l’environnement de dépôt et l’intérêt exo-biologique des sédiments étudiés.The exploration of the Martian surface by the rover Curiosity, at Gale crater, has unveiled past habitable conditions on the planet with evidences for sustained period of surface aqueous activity recorded in fluvio-lacustrine sedimentary deposits. In addition, the rocks also bear traces of the complex post-depositional evolution of the sediments during diagenesis, in the form of small-scale fracture-fills, nodules, and concretions that formed by sub-surface fluid circulations. On board, the rover, the Laser-Induced Breakdown Spectroscopy (LIBS) performed by the ChemCam instrument provide remote fine-scale chemical measurements, especially suited to the analysis of such geological items. This study demonstrates that the Ca-sulfate-bearing veins, observed across all geological terrains, show enrichments in Fe at specific locations along the rover traverse, tracing localized oxidizing conditions at the time of their formation in the later stages of diagenesis. Additionally, a key sedimentary structure in Gale crater is characterized by hematite spectral signatures from orbit, suggesting the involvement of redox-driven processes in its formation, either related to primary deposition or post-depositional conditions. There, in situ ChemCam observations highlight the mobility of Fe during diagenesis and the authigenic formation of Fe-oxide in association with Ca-sulfate bearing features. As such, this work attests of significant fluid interactions, and notably redox-driven chemical reactions, affecting the Martian sediments after their deposition and burial, which need to be taken into account in order to avoid any misinterpretations on the environment of deposition and its habitability

Editorial to the Topical Collection: Ocean Worlds

International audienceWe are at the beginning of a new era in the exploration of the outer solar system. Spacecraft have already visited each of the giant planets and made detailed observations of their major satellites. In 2017, the Cassini spacecraft ended its highly successful mission in the Saturnian system while the Juno mission has been investigating Jupiter since 2016. The New Horizons spacecraft revealed the Pluto/Charon system in 2015 and is now exploring the Kuiper belt. In parallel, NASA, ESA, and other international space agencies are considering the next major steps in the outer solar system exploration. Among these, the Jupiter Icy moon Explorer (JUICE), the first Large class mission of the ESA Cosmic Vision 2015-2025 campaign currently in development, will explore three satellites of the Jovian system-Ganymede, Europa and Callisto-to study the emergence of habitable worlds around gas giants. NASA is als

Geologic mapping and stratigraphy of remote Martian outcrops using digital outcrop model and virtual reality: example of the Kimberley outcrop (Gale Crater, Mars)

International audienceReconstruction 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

3D Digital Reconstruction of the Kimberley Outcrop (Gale Crater, Mars) from Photogrammetry using Multi-Scale Imagery from Mars Science Laboratory

International audienceStructure-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

Digital outcrop model reconstruction and virtual reality integration of the Kimberley outcrop (Gale Crater, Mars) for geological "in situ" analysis

International audienceStructure-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

3D Digital Outcrop Model reconstruction of the Kimberley outcrop (Gale crater, Mars) and its integration into Virtual Reality for simulated geological analysis

International audienceStructure-from-Motion photogrammetry has recently become a cheap and efficient method to reconstruct accurateand highly-resolved 3D Digital Outcrop Model (DOM) from a single set of images. This enables the 3D visualizationof hardly accessible and/or remote geological scenes, which is of strong interest for planetary bodies.This paper focuses on the reconstruction of the DOM of the Kimberley outcrop (Gale crater, Mars) using the AgisoftPhotoScan Professional software. This software is used to compute an accurate, scaled and georeferenced3D mesh of this outcrop from set of multi-scale images taken by the Mars Science Laboratory rover Curiosity.This model was merged with a 3D model computed from orbital images from the High Resolution Imaging ScienceExperiment camera (HiRISE) to provide the context. One of the challenges is to integrate data coming fromdifferent cameras (with varying optical parameters) not specifically designed for 3D rendering, and with limitedpoints of views. While the obtained DOM allows to observe and characterize geological features of Kimberley'ssedimentary series, classic viewing methods through a 2D screen limits the understanding of the real 3D geometryand scale of the outcrop, as there is no feature such as trees or roads on Mars to provide size references tothe user. To overcome this issue and facilitate the interpretation of the DOM, the latter is integrated into a VirtualReality (VR) environment that enables one or several users working in a collaborative mode to experiencea real scale, reliable and realistic depiction of the actual geometries of the geological features reconstructed onthe mesh. Precise and accurate description, contextualization of the samplings and mapping of the Kimberleyoutcrop can therefore be achieved in VR allowing for more precise characterization and interpretations, the sameway one would do on a real geological field trip

Using ChemCam LIBS data to constrain grain size in rocks on Mars: Proof of concept and application to rocks at Yellowknife Bay and Pahrump Hills, Gale crater

International audienc

Diagenesis of Vera Rubin Ridge, Gale Crater, Mars, From Mastcam Multispectral Images

International audienceImages from the Mars Science Laboratory (MSL) mission of lacustrine sedimentary rocks of Vera Rubin ridge on "Mt. Sharp" in Gale crater, Mars, have shown stark color variations from red to purple to gray. These color differences crosscut stratigraphy and are likely due to diagenetic alteration of the sediments after deposition. However, the chemistry and timing of these fluid interactions is unclear. Determining how diagenetic processes may have modified chemical and mineralogical signatures of ancient Martian environments is critical for understanding the past habitability of Mars and achieving the goals of the MSL mission. Here we use visible/near-infrared spectra from Mastcam and ChemCam to determine the mineralogical origins of color variations in the ridge. Color variations are consistent with changes in spectral properties related to the crystallinity, grain size, and texture of hematite. Coarse-grained gray hematite spectrally dominates in the gray patches and is present in the purple areas, while nanophase and fine-grained red crystalline hematite are present and spectrally dominate in the red and purple areas. We hypothesize that these differences were caused by grain-size coarsening of hematite by diagenetic fluids, as observed in terrestrial analogs. In this model, early primary reddening by oxidizing fluids near the surface was followed during or after burial by bleaching to form the gray patches, possibly with limited secondary reddening after exhumation. Diagenetic alteration may have diminished the preservation of biosignatures and changed the composition of the sediments, making it more difficult to interpret how conditions evolved in the paleolake over time

Diagenetic Processes in Sedimentary Rocks At Gale Crater, Mars, Using Chemcam, Curiosity Rover

International audienceWe describe the chemistry of diagenetic features using the ChemCam instrument to understand the post-depositional history of aqueous sedimentary rocks at Gale crater. These new observations display the significant role played by groundwater circulation and diagenesis in the mobility and distribution of iron in the Vera Rubin Ridge, highlighted here by reducing fluids observed late in the sequence of diagenesis