The European Space Agency published an image of an ice cliff near Mars's south pole on Mars Express, taken by the spacecraft's High Resolution Stereo Camera. The region, known as Thyles Rupes, appears in purple, pink and red tones rather than the tans and reds usually associated with the planet. ESA says the darker tones come from volcanic material rich in minerals such as olivine and pyroxene, while paler areas are covered by frosty carbon dioxide deposits that persist during Martian spring, when the region was imaged.

According to ESA, the purple hue results from a combination of soft morning light, dust in the atmosphere, ground frost and patches of mixed ice and dust. The cliffs rise over 1 km in places and are thought to be tectonic in origin, formed when parts of the Martian crust were pushed together as the planet's interior cooled. Some craters are cut by the cliffs while others lie on top of them.

Mars Express launched in 2003 and has mapped the planet in color and in three dimensions. The camera was developed and is operated by the German Aerospace Center (DLR), with image processing by the DLR Institute of Space Research and Freie Universität Berlin.