2 research outputs found
Sedimentology and Stratigraphy of the Shenandoah Formation, Western Fan, Jezero Crater, Mars
International audienceAbstract Sedimentary fans are key targets of exploration on Mars because they record the history of surface aqueous activity and habitability. The sedimentary fan extending from the Neretva Vallis breach of Jezero crater's western rim is one of the Mars 2020 Perseverance rover's main exploration targets. Perseverance spent âŒ250 sols exploring and collecting seven rock cores from the lower âŒ25 m of sedimentary rock exposed within the fan's eastern scarp, a sequence informally named the âShenandoahâ formation. This study describes the sedimentology and stratigraphy of the Shenandoah formation at two areas, âCape Nukshakâ and âHawksbill Gap,â including a characterization, interpretation, and depositional framework for the facies that comprise it. The five main facies of the Shenandoah formation include: laminated mudstone, laminated sandstone, lowâangle cross stratified sandstone, thinâbedded granule sandstone, and thickâbedded granuleâpebble sandstone and conglomerate. These facies are organized into three facies associations (FA): FA1, comprised of laminated and soft sedimentâdeformed sandstone interbedded with broad, unconfined coarserâgrained granule and pebbly sandstone intervals; FA2, comprised predominantly of laterally extensive, softâsediment deformed laminated, sulfateâbearing mudstone with lenses of lowâangle crossâstratified and scoured sandstone; and FA3, comprised of dipping planar, thinâbedded sandâgravel couplets. The depositional model favored for the Shenandoah formation involves the transition from a sandâdominated distal alluvial fan setting (FA1) to a stable, widespread saline lake (FA2), followed by the progradation of a river delta system (FA3) into the lake basin. This sequence records the initiation of a relatively longâlived, habitable lacustrine and deltaic environment within Jezero crater
Geological and Meteorological Imaging Results from the Mars 2020 Perseverance Rover in Jezero Crater
Perseveranceâs Mastcam-Z instrument provides high-resolution stereo and multispectral images with a unique combination of spatial resolution, spatial coverage, and wavelength coverage along the roverâs traverse in Jezero crater, Mars. Images reveal rocks consistent with an igneous (including volcanic and/or volcaniclastic) and/or impactite origin and limited aqueous alteration, including polygonally fractured rocks with weathered coatings; massive boulder-forming bedrock consisting of mafic silicates, ferric oxides, and/or iron-bearing alteration minerals; and coarsely layered outcrops dominated by olivine. Pyroxene dominates the iron-bearing mineralogy in the fine-grained regolith, while olivine dominates the coarse-grained regolith. Solar and atmospheric imaging observations show significant intra- and intersol variations in dust optical depth and water ice clouds, as well as unique examples of boundary layer vortex action from both natural (dust devil) and Ingenuity helicopterâinduced dust lifting. High-resolution stereo imaging also provides geologic context for rover operations, other instrument observations, and sample selection, characterization, and confirmation