This HiRISE images allows us to see this unusual geologic feature in three dimensions (2000 x 2000; 11MB).

The sequence of events that formed this scene in the equatorial lowlands of Mars are as follows. First, a meteorite impact excavated the 2.2 kilometer (1.4 mile) diameter crater in the center of the picture. Second, the area was flooded by a vast lava flow. However, the lava was not able to overtop the rim of the crater and it remained a large depression.

Third, the area was blanketed by a series of layers of small particles carried by the wind. This deposit makes up what is called the Medusae Fossae Formation and may be composed of volcanic ash. Finally, the Medusae Fossae Formation was largely eroded away by the wind. However, the deposits within the crater were protected from the wind and have remained to this day.

The hills outside the crater are also remnants of the Medusae Fossae Formation.
Written by: Laszlo P. Keszthelyi

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.