An amazing shot of a Martian dunescape. The dunes are dark grayish basalt. The red is typical Martian dust. The tendrils?
In the Martian winter, carbon dioxide freezes out of the air (and you thought it was cold where you are). In the summer, that CO2 sublimates; that is, turns directly from a solid to a gas. When that happens the sand gets disturbed, and falls down the slopes in little channels, which spreads out when it hits the bottom. But this disturbs the red dust, too, which flows with the sand. When it’s all done, you get those feathery tendrils. Note that at the tendril tips, you see blotches of red; that’s probably from the lighter dust billowing a bit before settling down.