Like the other major shield volcanoes on Mars, Arsia Mons has a caldera (large volcanic crater) at its summit.

Calderas form when magma (molten rock) is removed from the magma chamber in the volcano, and the roof of the magma chamber collapses into the resulting void. In the case of Arsia Mons, there are relatively young lava flows that overtop the northeast rim of the caldera.

This HiRISE image samples some of these lava flows. The long elliptical depression is the summit crater of a small shield volcano that fed some of these lava flows. At HiRISE resolution, we see that even these younger lavas are covered by a thick layer of dust. The small dark-rayed crater in the southwest edge of the image shows that the rock under the dust is dark, as expected of lava.

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.