This image shows the floor of an unnamed impact crater in Arabia Terra that has layered deposits. There are many craters in this region where layering is observed.
These layers are often exposed along the sides of large isolated mounds, small knobs and mesas, and other positive relief features. In some cases, the layering is expressed as narrow sinuous ridge-like structures along crater floors.
The presence of layered deposits is of particular interest because these materials are not likely to be related to the impact event, but rather post-impact infill of the crater. Modification of the deposits has now revealed layers of material.
HiRISE and other instruments onboard the Mars Reconnaissance Orbiter may provide more clues to the origin of the these deposits.
Written by: Frank Chuang (13 August 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_008982_1965
Image: NASA/JPL/University of Arizona