Just expand this image a little bit and you'll see amazing detail — that's frost forming on ripples of sand, its distinctive wrinkly appearance created by wind whipping along this slope on the inside of a Martian crater.
Image credit: NASA/JPL/University of Arizona
This image was captured last month by the HiRISE camera on the Mars Reconnaissance Orbiter (MRO), and shows a south-facing area inside the crater that's "approximately 1.5 by 3 kilometers." MRO researchers explain:
At this time of year only south-facing slopes retain the frost, while the north-facing slopes have melted. Gullies are not the only active geologic process going on here. A small crater is visible at the bottom of the slope.
Learn more about HiRISE on the official website.