The bright rock exposures in this image occur along the walls of a 60-kilometer diameter impact crater.
The crater penetrated into rocks that are made of different kinds of sulfates. The sulfates appear brighter than most other rocks commonly found on Mars, like basaltic lava flows. Within the sulfates there may be small particles (below the 25 centimeter/pixel resolution of HiRISE) composed of iron in the form of hematite (Fe2O3).
Scientists are able to use spectral information from instruments like the Compact Reconnaissance Imaging Spectrometer for Mars ( CRISM ) and the Thermal Emission Spectrometer ( TES ) to identify minerals like sulfates and hematite on the surface of Mars. The occurrence of these two minerals at this location suggests that water once existed here in the past.
Written by: Cathy Weitz (2 June 2010)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_017384_1670
Image: NASA/JPL/University of Arizona