This image covers a pit in the lower west flank of Arsia Mons, one of the four giant volcanos of the Tharsis region.

Many layers are exposed in the pit, probably marking individual lava flows, and provide information about the nature of the volcanic eruptions. This image was acquired in the middle of large regional dust storms on Mars, but the atmosphere over this image is only moderately dusty because the altitude is 6.5 kilometers higher than the planetary mean, so the air is quite thin and cannot hold as much dust.

Although the atmosphere is not too dusty, the surface is buried by a dust layer meters thick. These high-altitude locations on Mars have thick dust deposits because the thin air cannot blow away the dust, or at least not as fast as it accumulates. On Earth the oceans serve as dust traps, but on Mars, it is the high volcanos.
Written by: Alfred McEwen

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.