This image shows part of the floor of a large crater in Terra Tyrrhena. Here, dark mesas contrast with light-colored, topographically lower outcrops.

The mesas have sharp cliffs, indicating the dark materials are not loose, but rather consolidated; layering is also visible along the cliffs. The underlying light materials are also layered and profusely fractured. Their superposition relationship indicates that the light materials are older than the dark, mesa-forming materials.

The image also shows a number of crest-like features criss-crossing the landscape. The fact that their relief is so prominent indicates they are more resistent to erosion (harder) than their surroundings. These crests could be indurated fractures (fractures cemented by fluids) or dikes. Dikes are tabular intrusions of rock formed when underground magma is injected along fractures.

The lowest regions in the image are covered by dark-colored dunes (see for instance the NW or upper left section of the image). These are possibly accumulations of fine-grained materials eroded-out from the mesas.
Written by: Kelly Kolb

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.