Mars is cold, mostly dry, and a place where liquid water appears only fleetingly. Korolev crater holds a veritable reservoir almost 1.1 miles (1.8 km) thick in places.
This remarkable photograph is a five different image strips recombined into one that reveals the 51-mile (82 km) wide crater and its ever-present sheet of ice. When the thin air settles over the ice, it cools down and creates a chilly layer that behaves as a shield, keeping Korolev continuously icy.
The images that make up the image were recorded by the European Space Agency's Mars Express orbiter, which has been snapping pictures of the Martian surface since 2003.
Korolev is named after the enigmatic rocket engineer Sergei Korolev, who led the United States by launching Sputnik and later Yuri Gargarin into orbit. He spent years as a prisoner in Siberia before being released in 1944 to continue his work in aircraft design. He died in 1966 after complications from a minor operation.