Observations by NASA's Mars Reconnaissance Orbiter have detected carbon-dioxide snow clouds on Mars and evidence of carbon-dioxide snow falling to the surface.
Deposits of small particles of carbon-dioxide ice are formed by snowfall from carbon-dioxide clouds. This map shows the distribution of small-grain carbon-dioxide ice deposits formed by snowfall over the south polar cap of Mars. It is based on infrared measurements by the Mars Climate Sounder instrument on the Mars Reconnaissance Orbiter.
Image credit: NASA/JPL-Caltech
Note: For more information, see NASA Observations Point to 'Dry Ice' Snowfall on Mars.