Curiosity's Three-Frame Mosaic of Clouds
NASA's Curiosity Mars rover imaged these drifting clouds on May 17, 2019, the 2,410th Martian day, or sol, of the mission, using its black-and-white Navigation Cameras (Navcams).
These are likely water-ice clouds about 19 miles (31 kilometers) above the surface. They are also "noctilucent" clouds, meaning they are so high that they are still illuminated by the Sun, even when it's night at Mars' surface. Scientists can watch when light leaves the clouds and use this information to infer their altitude.