Features in Nili Fossae

Nili Fossae is a system of deep fractures around the giant Isidis impact basin. The deepest are 500 m incisions into the martian crust (1). A strongly eroded large impact crater is visible on the northeastern edge of the area (2) measuring about 12 km across. This crater exhibits an ejecta blanket, usually formed by material thrown out during the impact. In addition, two landslides to the west of the crater can be seen, either triggered by the impact or possibly later. In contrast, a smaller impact crater southwest of the fractures measuring just 3.5 km in diameter shows no ejecta blanket (3): it may have been eroded or buried. The surface material on the southwestern image border is much darker than the rest of the area (4). It is probably basaltic rock or volcanic ash originating from Syrtis Major.