Carbon dioxide frost

Carbon dioxide frost dusts the dunes near Mars's Proctor Crater in a recently released picture taken by the Mars Reconnaissance Orbiter.

As the red planet moves into spring, frost that accumulated during winter evaporates, although some can remain in regions sheltered from direct sunlight.

The orbiter first took pictures of these same dunes in 2006. Studying changes in an area's frost patterns over the years can help scientists better understand seasonal variability on Mars.