powers of four

Winter View of Dunes (PSP_001558_1325)
Credit: NASA/JPL/University of Arizona

Dunes within a crater on Mars are visible in this HiRISE image. This crater is located in the southern hemisphere where it was winter at the time this image was taken.

This observation documents new seasonal processes occurring on dunes at this latitude, as well as other interesting phenomena. The bright tones are interpreted as carbon dioxide or water frost. This is generally concentrated on the east-facing slopes of the dunes, which are in shadow and therefore cooler. Some dark spots on the dunes may be areas that have defrosted more than surrounding terrain.