A Piece of Mars: Normally I post in color, but sometimes you need to back out to the grayscale images to see the big awesome things. This scene is 4.6×2.6 km (2.8×1.6 mi); the conical hill is 1.4 km (0.89 mi) wide. Sand-laden wind from the right is blowing streamers of dunes around the hill, which leaves a wake that stretches downwind. Some of the luckier hills on Mars have lovely dunes scarves like this, slowly shifting over the centuries as the wind brings in more sand. (HiRISE ESP_044258_1715 NASA/JPL/Univ. of Arizona)