"The image shows a typical region of northern plains covered by polygons and boulders. There are dark areas in low spots that are probably due to windblown dark sand. Where the sand is most abundant, it forms the dunes seen near the top and bottom of this image. The "white smudge" appears to be a region with relatively little dark sand. It isn't actually white, but it is brighter than other nearby regions. These could be low hills where the sand doesn't collect."
Image: NASA/JPL/University of Arizona
Written by: Alfred McEwen (6 June 2012)