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Changes on the Martian surface are detected by imaging the same area more than once. In this image acquired on May 13, 2018, NASA's Mars Reconnaissance Orbiter observes several new dust avalanches on the slopes of ridges within the Olympus Mons Aureole. These changes occurred within six years. (Also see the animated GIF).

Dust avalanches create slope streaks that expose darker materials usually hidden below a lighter-toned layer. Cascading fine-grained material easily diverts around boulders or alters direction when encountering a change in slope (see the top right corner of the first close-up). The dark steak in another close-up is approximately 1 kilometer in length that not seen in a previous image. Past avalanche sites are still visible and fading slowly as dust settles out of the atmosphere and is deposited on the dark streaks over time.

Also seen are boulders and their shadows that are a meter or greater in size. Movement of any of these boulders down the slope could trigger future avalanches.

The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. [The original image scale is 56.7 centimeters (22.3 inches) per pixel (with 2 x 2 binning); objects on the order of 170 centimeters (66.9 inches) across are resolved.] North is up.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.