Dust-devils are vortices of wind that form when air rising from a warm surface encounters shear in the above atmosphere. Martian dust devils can attain gargantuan proportions, reaching the size of terrestrial tornadoes with plumes that tower up to 9 kilometers above the surface. Dust-devils play an important role in sustaining the aerosols that make up Mars' red sky and in cleaning the Martian surface after a dust storm. This observation shows a region near the Martian equator. Image Credit: NASA/JPL/University of Arizona