Multi-scale Spectral Characterization of Clay-Rich Crater Walls in Oxia Planum

Abstract

Oxia Planum is the chosen landing site for the European Space Agency’s ExoMars Rosalind Franklin rover mission for its evidence of multi-episodic sustained aqueous activity and astrobiological potential. Previous works have aimed to characterise various mineralogical and morphological units present in Oxia Planum. Two distinct clay-bearing units have been identified based on spectral and morphological variations: an orange and a blue unit. The blue unit stratigraphically overlies the orange unit, and while they are similar texturally, they exhibit some subtle textural as well as spectral differences from one another.Compositionally, the orange unit is associated with the strongest clay signatures, while the blue unit appears to be consistent with a clay signature mixed with a mafic component. Several hypotheses have been proposed to explain their formation, including pedogenesis, groundwater alteration, and subaqueous sedimentation of either authigenic or clastic nature. However, these scenarios need to be further constrained and may also need to be further expanded to include clay formation under less warm and wet conditions on early Mars. Impact craters serve as windows into the subsurface by excavating, uplifting, and exposing materials that may not be visible at the surface. In this study, we use impact craters to investigate local and regional variations in the stratigraphy of Oxia Planum.