DEPOSITIONAL HYPOTHESES FOR THE EMPLACEMENT OF THE MARGIN UNIT, JEZERO CRATER, MARS

Abstract

International audienceAfter 910 sols, the Mars 2020 Perse-verance rover has begun exploring the margin unit, the region with the strongest and clearest orbital signature of carbonate minerals (Figure1) [1, 2]. Stratigraphically, the margin unit is older than the Upper Delta/Fan Top units and lies unconformably below curved and inclined sandstone deposits, interpreted as fluvial deposits, and below the boulder-rich unit (Figure 2). On Mars, rovers and orbiters have only detected carbonates in trace amounts in only a few locations on the surface [3]; how-ever, their sources are primarily unclear. Some car-bonate material is also found in martian meteorites such as ALH 84001 and Nakhla [3]. The sources are aqueous alteration of igneous material, both in Comanche rock and ALH84001 [3]. Carbonates generally form due to aqueous processes in solutions that contain inorganic carbon. However, the meteorites do not preserve a rec-ord of specific surface processes in past habitable envi-ronments. Based on orbital detections, the carbonate material in Jezero is hypothesized to have precipitated from a lacustrine environment [1]