Scarp-fronted deposits record the highest water level in Mars’ Valles Marineris

We investigated the geomorphology of the promontory and the sedimentology of scarp-fronted deposits (SFDs) in Southeast Coprates Chasma using CTX, HiRISE, and CaSSIS images, and DEMs based on CaSSIS stereo pairs, HRSC and MOLA data. In the promontory, we find a network of branched channels bordered by screes and bedrock along the drainage divides, indicating a fluvial origin. The SFDs, occurring at the downstream end of the promontory, display convex break-in-slopes, separating a flat surface with a radial drainage network from a steep front downstream. We interpret these structures as records of fan-deltas with sources in the promontory, recording a sea-level high-stand. Notably, all identified SFDs occur at the same elevation range (-3750 to -3650 m) in Valles Marineris and the northern lowlands, and they were deposited between the Late Hesperian and the Early Amazonian. We consider this as the time with the largest availability of surface water on Mars.