This observation features an exhumed crater in Meridiani Planum, an equatorial region where the MER Rover Opportunity has been exploring the Martian surface since January 2004.

An exhumed crater is one that formed a long time ago and was later infilled with materials and buried. Subsequent erosion has caused this crater to become exposed at the surface once again.

The crater interior contains a sequence of layers (see subimage, upslope is to the right, approximately 420 meters across; 1676 x 1344, 6MB) that are remnants of the material that originally filled the crater. The layers were deposited then became cemented as overlying layers pressed them down. The sequence of layers has not eroded evenly because different layer compositions and other factors, such as cementation and chemical alteration, can make certain locations more resistant to erosion.

For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.