Dust devils leave tracks behind them that create the beautiful swirling patterns visible here (approximately 0.5 kilometers, or 0.3 miles across) and in many other images of dust-covered terrain. Suction created by the air rotating in a whirlwind removes a thin layer of light-colored dust from the Martian surface, leaving behind dark lines in the dust devil’s path.
That’s what usually happens. In this case, however, there is an unusual streak that appears brighter at one end (approximately 0.6 kilometers or 0.4 miles across, and north is roughly upwards).
The bright streak could be a deposit of light-colored material that the dust devil dropped for some reason: maybe the dust devil died out right at this spot. Or it could be that at this particular location, the underlying dune is brighter than the dust on top of it, so when the dust devil removed the surface layer, a brighter layer below was revealed. Or there could be some other explanation we haven’t even thought of yet!
Numerous small slope streaks are also visible in this image; for example, on the left side of the subimage, white arrow . These are thought to occur when a thin layer of dust avalanches downhill, revealing darker material beneath. Over time, these streaks, like dust devil tracks, slowly brighten to match their surroundings, as dust is deposited from the atmosphere to cover them.
Written by: Ingrid Daubar (19 October 2011)
This is a stereo pair with ESP_023261_2065 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_023327_2065
Image: NASA/JPL/University of Arizona