This series of images spanning a period of 15 weeks shows a pair of fresh, middle-latitude craters on Mars in which some bright, bluish material apparent in the earliest images disappears by the later ones. Each panel is 75 meters (246 feet) across. The two craters are each about 4 meters (13 feet) in diameter and half a meter (1.5 feet) deep.
The bright material is water ice that was uncovered by the meteorite impact that excavated these small craters less than 15 weeks before the initial image of this series. Sublimation of the ice during the Martian summer leaves behind a dust layer that gradually thickens to the point where it obscures the ice.
The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took these images of this site at 46.33 degrees north latitude, 176.90 degrees east longitude. The HiRISE camera's targeting of the site was prompted by two earlier images from the Context Camera on the Mars Reconnaissance Orbiter, which showed that the impact responsible for these craters had not yet occurred by June 4, 2008, but had occurred by Aug. 10, 2008.
The dates when these six HiRISE images were taken were (left to right, top row; then left to right, bottom row): Sept. 12, 2008; Sept. 28, 2008; Oct. 9, 2008; Oct. 14, 2008; Nov. 22, 2008; and Dec. 25, 2008. The span of time corresponded to a period from mid to late summer in Mars' northern hemisphere. The images are subframes of the observations made on those dates. The full-frame images are online (same order) at http://hirise.lpl.arizona.edu/PSP_009978_2265; http://hirise.lpl.arizona.edu/PSP_010189_2265; http://hirise.lpl.arizona.edu/PSP_010334_2265; http://hirise.lpl.arizona.edu/PSP_010400_2265; http://hirise.lpl.arizona.edu/PSP_010901_2265; and http://hirise.lpl.arizona.edu/ESP_011323_2265.
Image Credit: NASA/JPL-Caltech/University of Arizona
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