Clouds on Mars

This true-colour view taken by NASA's Pathfinder rover in August 1997 shows clouds in the Martian eastern sky (30 degrees above the horizon), as imaged before sunrise.

Observations of the Martian atmosphere by the SPICAM spectrometer on board ESA's Mars Express spacecraft, have revealed for the first time that carbon dioxide clouds form and exist at very high atmospheric layers, between 80 and 100 kilometres above the Martian surface. This makes them the highest clouds ever observed above any planetary surface. These clouds may be of the same type observed by Pathfinder.