These dunes in Aonia Terra are being monitored for changes such as gullies, which form over the winter from the action of carbon dioxide frost.
The season in which this image was acquired was late fall in the Southern hemisphere. Frost is just starting to accumulate here, and is concentrated on pole-facing slopes and in the troughs between the meter-scale ripples.
The colors have been enhanced in the subimage .
Written by: Alfred McEwen (22 February 2012)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_025679_1300
Image: NASA/JPL/University of Arizona