A Martian polar landscape

This exotic landscape is located on Mars' South Pole, but its features are similar to ones found on Earth, such as river valleys, cliffs, glaciers and volcanoes. The polar cap is made from carbon dioxide, or dry ice, which does not occur naturally on
PHOTO: AGENCE FRANCE-PRESSE

This exotic landscape is located on Mars' South Pole, but its features are similar to ones found on Earth, such as river valleys, cliffs, glaciers and volcanoes.

The polar cap is made from carbon dioxide, or dry ice, which does not occur naturally on Earth.

Within the layer of dry ice are holes that expand by a few metres each Martian year, producing what look like circular pits in this Nasa image.

New dry ice is constantly added to the landscape, either by freezing directly out of the carbon dioxide atmosphere or by falling as snow.

Freezing out the atmosphere like this limits how cold the surface can get to the frost point at -130 deg C. Nowhere on Mars is colder, making this the coldest landscape on Earth and Mars combined.

A version of this article appeared in the print edition of The Straits Times on December 16, 2016, with the headline 'A Martian polar landscape'. Print Edition | Subscribe