Gale Crater is a large, approximately 152 kilometer-diameter impact crater that lies near the Martian equator. Contained within the crater is a massive central mound of layered material. With an average vertical thickness of almost 4 km (2.4 miles), the Gale Crater layered deposits are twice as thick as the layers exposed along the Grand Canyon on Earth.

Shown here is a portion of the mound with an inverted fluvial or river channel. Topographic inversion occurs when sediments are cemented together, forming a harder layer that is resistant to later erosion. This later erosion has preferentially removed material outside the channel, leaving the former riverbed exposed as a ridge—a topographic high. This inverted channel was originally detected by scientists using Mars Orbiter Camera (MOC) images onboard the Mars Global Surveyor spacecraft.

Color variations visible in this image are mostly due to variable amounts of loose dark sediment that has accumulated unevenly across the scene.
Written by: Brad Thomson

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.