Clouds pass above a cliff face on Mars in this recent image from the Curiosity rover, which has been operating on Mars since 2012. The image consists of 21 individual frames, and has been color-balanced to show the scene as it would look to the human eye. The clouds are at high altitudes, suggesting they're made of frozen carbon dioxide (dry ice), not water. Clouds are rare on Mars, but do show up at some times of year. [NASA/JPL/MSSS]