Valleys, deltas, and lacustrine sediment in the southwestern Melas Basin, Valles Marineris

Planetary Geomorphology Image of the Month, July 30, 2015: Joel Davis (University College, London, UK). During the last few decades, dry river valley networks and delta fan structures have been found to be increasingly common on ancient terrains on the martian surface (e.g. Goldspiel and Squyres, 1991; Hynek et al., 2010). They are considered to be one of the main lines of evidence that Mars once had Earth-like precipitation and surface runoff (e.g. Hynek and Phillips, 2003). One such location is the south-western Melas basin, part of a collapsed graben structure on the southern wall of Melas Chasma, Valles Marineris – Mars’ equatorial canyon system. The basin likely formed in the early Hesperian period (~ 3.7 – 3.5 Ga), soon after Melas Chasma opened. [More at link]