Dune-Gullies in Matara Crater (EDM - Approx. True Colors; credits for the additional process. and color.: NASA/JPL/University of Arizona)

Caption NASA:"This image shows changing Dunes and incised Gullies (so-called "Dune-Gullies") in the Southern Matara Crater.
Repeat imaging of the Dunes in this Crater shows that material towards the top of the Gullies has moved downslope and the Channel Beds may have widened over time.

Since this activity occurs during Martian Southern Hemisphere Winter, it is believed to be related to Carbon Dioxide (CO2) Frost that forms as the area grows colder. Scientists continue to monitor this specific Region for changes in the Gullies and the Dunes themselves. This frame is approx. 1 (one) Km (0,6 miles) across".