Reconstruction of the Subsurface Stratigraphy of the ExoMars Oxia Planum Landing Site Through Investigations of Exposed Bedrock Within Crater Walls

Kurzfassung

The European Space Agency (ESA) is sending the next rover to Mars in 2028, named Rosalind Franklin, as part of the ExoMars mission. The main aim of the rover is to look for signatures of past aqueous activities on Mars that may have provided habitable environments for life. To meet these objectives, Oxia Planum was the chosen landing site for this rover because of its widespread Fe/Mg phyllosilicate exposures, ancient Noachian-aged rocks and strong evidence of prolonged fluvial activity [1-3]. Oxia Planum is a low-lying plain between Chryse Planitia and Arabia Terra, at the outlet of Coogoon Vallis [4-5]. It has witnessed at least two episodes of fluvial activity; one associated with the deposition/alteration to form the widespread clay unit and, the second, as evidenced by a remnant fluvial-deltaic fan deposit found on the outlet of Coogoon Vallis [6-7]. Based on HiRISE (High Resolution Imaging Science Experiment) colour-infrared observations, previous studies have reported two subunits of clays with a bluish (more ferrous-bearing) and orange (more ferric-bearing) appearance, wherein the orange subunit lies atop the blue subunit [3,9,10]. There is evidence of compositional differences between the two subunits that suggests varying post-deposition aqueous alteration or different detrital material provenance [9,11,12].