On an early fall afternoon in Ganges Chasma (Valles Marineris), we managed to capture a cluster of 8 dust devils, five of them in the enhanced color strip. They’re together on a dark sandy surface that tilts slightly to the north, towards the Sun.
Both of these factors help warm the surface and generate convection in the air above. The surface is streaked with the faint tracks of earlier dust devils. A pair of dust devils appears together at top right, spaced only 250 meters apart. These two have quite different morphologies. The bigger one (on the right) is about 100 meters in diameter and is shaped like a doughnut with a hole in the middle. [More at link]