One of the most important processes on present-day Mars is wind. Aeolian (wind-related) features are found in most regions of the planet. This image shows a diverse array of such features: large dunes, small ripples, and dust-devil tracks (the dark, arcing structures on the dunes).
Dust devils form in many parts of Mars, but they are often particularly distinct on sand dunes. One possibility is that the dust devils dislodge a small amount of fine dust, making the color of dark sand more prominent.
Ripples of wind-blown sand form regular patterns. In the simplest case, wind blowing in a constant direction creates evenly spaced straight ripples at right angles to the wind. More complex wind patterns create more complex ripples, and in this scene variations from linear to polygonal to checkerboard patterns are visible.
This image is particularly interesting because of the occurrence of seasonal frost on the south-facing slopes. (The image is in the southern hemisphere, so south faces the pole and gets little winter light). This is particularly apparent in the color swath, as the frost forms pale, purplish patterns. On the dunes, this highlights some of the regular patterns, as the frost forms only on parts of the ripples. The result is an intricately textured pattern of color.
Written by: Colin Dundas (26 November 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_010221_1420
Image: NASA/JPL/University of Arizona