Oh, gravity, the things you can do

A piece of Mars: Steep slopes in some parts of Mars are prone to very thin landslides that leave behind dark tracks. The landslides may be triggered by the wind or nearby impacts. They always move downslope — in this case from upper left to lower right, meandering around craters and lapping up against old, stabilized dunes. The darkest one here is brand new, having formed sometime between 2007 and 2012. (HiRISE ESP_028642_1800)