The parallel sides and low interior seen in this VIS image are faults and down-dropped material between the faults. This tectonic feature is called a graben. The graben in this image is located in Daedalia Planum.
Orbit Number: 49402 Latitude: -27.6842 Longitude: 233.651 Instrument: VIS Captured: 2013-02-01 19:18
Photo credit: NASA/JPL/Arizona State University