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The aureole that surrounds the western and northern sectors of Olympus Mons has puzzled Mars geologists. The most common idea is that these deposits formed as giant land slides as the volcano partially collapsed under its own weight.

This HiRISE image (PSP_003450_1975) is centered on a dark and relatively dust-free part of the aureole. Where the dust has been stripped off, swirling bands of darker and lighter rocks are visibile. These suggest gently warped layers that have been exposed by erosion. In fact, many of the small pinnacles and mesas in this area are being eroded by the wind in the same way as layered deposits in other parts of Mars. However, there are also blocks that shed dark material, that could be broken up lava rock. The many dunes in the area suggest that much of the debris is sand sized.

Observation Toolbox
Acquisition date: 4 April 2007
Local Mars time: 3:28 PM
Degrees latitude (centered): 17.4°
Degrees longitude (East): 216.7°
Range to target site: 280.7 km (175.5 miles)
Original image scale range: 28.1 cm/pixel (with 1 x 1 binning) so objects ~84 cm across are resolved
Map-projected scale: 25 cm/pixel and north is up
Map-projection: EQUIRECTANGULAR
Emission angle: 2.9°
Phase angle: 64.6°
Solar incidence angle: 62°, with the Sun about 28° above the horizon
Solar longitude: 223.8°, Northern Autumn

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.