The visible and near-infrared mapping spectrometer, OMEGA, on ESA’s Mars Express observed a curious cloud formation that appears regularly in the vicinity of the Arsia Mons volcano.
This water ice cloud, which arises as the volcano slope interacts with the air flow, can be seen as the white, elongated feature in the lower left part of the image, extending westward of the volcano and casting a shadow on the surface. The image was taken on 17 September 2018, from an altitude of 11 000 km. North is up.
More information: Mars Express keeps an eye on curious cloud