The Mars Reconnaissance Orbiter’s (MRO) high resolution imaging camera (HiRISE) photographed these gullies on Mars to compare them to previous instances. Scientists from NASA and the University of Arizona have been studying this data and have found changes in many gullies on Mars showing the constant evolution of the various Martian landforms. Changes often occur in winter or early spring, suggesting that they may be caused by the carbon dioxide frost that forms in and around most of these Martian gullies every year.