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Ascreaus Mons is one of the giant shield volcanoes in the Tharsis region of Mars. Based on earlier lower resolution images, this location seemed to be ideal for examining how different types of lava flows interacted.
The smoother ground on the northwest side of the image is probably a lava flow with a relatively smooth crust much like "pahoehoe" lava flows in Hawaii.
The rugged terrain in the southwestern part of the image is indicative of a highly disrupted crust, possibly like what Hawaiians call an "aa" flow. Instead of confirming these hypotheses, HiRISE shows that the lava flow details are obscured by dust. The dust is carved into a curious network of scallops that are too small to have been seen by previous cameras.
This is HiRISE image PSP_002209_1865.
Acquisition date: 1 January 2007
Local Mars time: 3:38 PM
Degrees latitude (centered): 6.6°
Degrees longitude (East): 26.6°
Range to target site: 265.5 km (165.9 miles)
Original image scale range: 26.6 cm/pixel (with 1 x 1 binning) so objects ~80 cm across are resolved
Map-projected scale: 25 cm/pixel and north is up
Emission angle: 1.0°
Phase angle: 55.3°
Solar incidence angle: 54°, with the Sun about 36° above the horizon
Solar longitude: 167.2°, Northern Summer
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.