This observation shows the complex, gullied western wall of a kilometer-deep impact crater in the Terra Sirenum region. This is an interesting crater because it appears to be mantled by the fluidized ejecta blanket of a slightly smaller crater just to the west.
A diverse set of gullies originate at multiple elevations along the crater wall. Prominent gullies have incised through the overlying ejecta into the upper walls to reveal numerous resistant dark layers. The floors of these gullies display a host of interesting features, including braided middle reaches, cut banks, channel bars, and stream terracing. These are all features suggestive of water flow.
Miniature gully systems, less than a kilometer long, start much further downslope than the larger gullies yet display the usual gully attributes, including theater-headed alcove source regions, incised middle reaches, and overlapping alluvial fans at their lower reaches. Detailed studies of these and other gully systems should help to elucidate the gully formation mechanisms.
Photo credit: NASA/JPL/University of Arizona