Image credit: NASA/JPL-Caltech/Univ. of Arizona
This image from NASA's Mars Reconnaissance Orbiter (MRO) shows streaks forming on slopes when dust cascades downhill. The dark streak is an area of less dust compared to the brighter and reddish surroundings. What triggers these avalanches is not known, but might be related to sudden warming of the surface.
These streaks are often diverted by the terrain they flow down. This one has split into many smaller streaks where it encountered minor obstacles.
Source / Image Courtesy