A Massive Ice-Filled Crater on Mars

ESA’s Mars Express mission recently photographed the Korolev crater on Mars, filled almost to the brim with water ice.¹ When I first saw this image I thought, oh cute!, assuming the crater was maybe a few dozen feet across. But no, it’s about 51 miles across and the thickest part of the ice is over a mile thick.

This ever-icy presence is due to an interesting phenomenon known as a ‘cold trap’, which occurs as the name suggests. The crater’s floor is deep, lying some two kilometres vertically beneath its rim.

The very deepest parts of Korolev crater, those containing ice, act as a natural cold trap: the air moving over the deposit of ice cools down and sinks, creating a layer of cold air that sits directly above the ice itself.

Behaving as a shield, this layer helps the ice remain stable and stops it from heating up and disappearing. Air is a poor conductor of heat, exacerbating this effect and keeping Korolev crater permanently icy.

Update: Just to clarify slightly, the top image was generated using photographs taken by Mars Express and a terrain map, so it’s technically not a photograph but is like the oblique view in Google Maps. The bottom image is a composite of five photographs. (via @ryanguill)

1. Mars also has CO2 ice, so you have to specify.↩

• Mars
• Mars Express
• space