This image shows a large outcrop of layered rock in Tithonium Chasma, a part of the Valles Marineris trough system.

Light, layered sediments are found at many sites on the floor of Valles Marineris. Observations drawn from this image will help understand the history of deposition at this location, and can be compared with nearby related rocks.

A light-toned unit (tan in the RGB color image) is found through most of the image. At high resolution, this unit often shows thin layers; it resembles light deposits found at many other sites. The light-toned materials are overlain by a dark unit (blue in the RBG color) that may have been deposited over the lighter rock much later. Variations in tone and color may indicate deviations in rock properties, such as the source material, cementation, or deposition process; in some cases they may simply be due to varying amounts of dust cover.

It is still unclear how the layered rocks in Valles Marineris formed. They might be sediments laid down in lakes or streams, wind-deposited, or volcanic materials. All of these processes can form layered rocks on Earth.

The dark material in the western part of the image appears to have once been a continuous layer over the current topography, now being eroded; if it was indeed draped, rather than laid down horizontally, it was most likely formed by dust or volcanic ash settling uniformly out of the atmosphere.
Written by: Colin Dundas

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.