These color-enhanced views of Deimos, the smaller of the two moons of Mars, result from imaging on February 21, 2009, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The two images were acquired 5 hours and 35 minutes apart, at an image scale of ~20 m/pixel. The sun was to the upper left in the first (left) image, and to the right in the second image.
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 downslope movement of regolith.
These images are products from observations catalogued by the HiRISE team as ESP_012065_9000 and ESP_012068_9000.