Martian dust devils were first photographed by the Viking orbiters in the 1970s. In 1997, the Mars Pathfinder lander detected a dust devil passing over it. In the first image below, photographed by the Mars Global Surveyor, the long dark streak is formed by a moving swirling column of Martian atmosphere. The dust devil itself is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.