The bottom of Olympus Mons, the largest volcano in the solar system, is marked by a steep scarp. It is likely that this scarp is the result of the deformation and collapse of the volcano under its own weight.

The scarp exposes the internal structure of the volcano, revealing a stack of once deeply buried lava layers. Atop the lava flows is a thick layer of relatively weak and homogeneous material, that might be volcanic ash or dust carried by dust storms. The pit near the center of the image shows that the same basic layering extends for some distance up the flank of the volcano.

The pit must be more recent than the dust/ash layer since the pit cuts through that layer. While it is possible that the pit is very recent, this suggests that the mantling layer is quite old.
Written by: Laszlo P. Keszthelyi

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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.