This images shows a Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) full-resolution "targeted image" of the edge of Mars' north polar cap. The region in the image, Chasma Boreale, is a valley several kilometers or miles deep that cuts about 400 kilometers (about 250 miles) into the edge of the cap. Credit: NASA/JPL/JHUAPL. Click to enlarge.
