This “etch-a-sketch” appearance indicates the presence of dust devil activity in the Thyles Rupes region of Mars.
The dark streaks are a result of a surface-atmosphere interaction that creates thermally-driven vortices. These Martian vortices are giant dust devils that “vacuum” the bright surface dust revealing the darker subsurface rock.
This image was taken in the late southern summer and shows that the dust devil direction of movement changes with the winds as the season progresses from spring to fall. Dust devils are sensitive to changes in low-speed ambient winds and will follow the dominant daytime wind direction.
The direction of the vortex is visible by the scallop pattern that is left behind as a dust devil will erase the front part of the circular track as it follows the wind.
Photo credit: NASA/JPL/University of Arizona
Note: Thyles Rupes is a set of two long scarps in the southern highlands that runs between Planum Australe and Promethei Terra. The closest named feature to Thyles Rupes is Burroughs Crater, which is close to the southern-most end of the southern scarp. Prior to 1984, Thyles Rupes had been named Ultimi Cavi [Hollows] and Thyles Chasma.
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