These color-enhanced views of Deimos, the smaller of the two
moons of Mars, result from imaging on Feb. 21, 2009, by the High
Resolution Imaging Science Experiment (HiRISE) camera on NASA's
Mars Reconnaissance Orbiter. Deimos has a smooth surface due to
a blanket of fragmental rock or regolith, except for the most
recent impact craters. It is a dark, reddish object, very
similar to Mars' other moon, Phobos. For a comparison, see
HiRISE images of Phobos taken March 23, 2008. These Deimos
images combine HiRISE exposures in near-infrared, red and blue-
green wavelengths. In the enhanced color, subtle color
variations are visible -- redder in the smoothest areas and less
red near the fresh impact craters and over ridges of topographic
highs (relative to Deimos' center of gravity). The color
variations are probably caused by exposure of surface material
to the space environment, which leads to darkening and
reddening. Brighter and less-red surface materials have seen
less exposure to space due to recent impacts or