This HiRISE sub-image shows layering in a light-toned deposit in Melas Chasma.

The layers are sedimentary in origin, but there are many processes that could have deposited them, such as volcanic airfall from explosive eruptions, dust-size particles settling out of the atmosphere due to cyclic changes, and deposition in standing bodies of water.

By looking at the slopes in the layers and how the layers intersect each other, scientists can rule out various origins. A darker material can be seen covering much of the layered deposit. Some of this dark material is loose and can be seen accumulating as debris aprons at the base of steep slopes. Other dark material appears indurated and has been eroded by the wind to form etched edges with topographic expressions.

The lack of impact craters on the layered deposit indicates that it is a relatively young deposit, or the craters have been removed by the wind, or the deposit was quickly buried and is now being exhumed.
Written by: Cathy Weitz

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible: Image: NASA/JPL/University of Arizona

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.