This stunning space wallpaper shows a region of the planet’s northern hemisphere known as Hephaestus Fossae – after the Greek god of fire – that was imaged by the high-resolution stereo camera on ESA’s Mars Express orbiter on Dec. 28, 2007. The image has been colored to indicate the elevation of the terrain: green and yellow shades represent shallow ground, while blue and purple stand for deep depressions, down to about 4 km. Scattered across the scene are a few dozen impact craters that cover a wide range of sizes, with the largest boasting a diameter of around 20 km. Scientists believe that only the most powerful impacts — those responsible for forging the largest craters — were able to dig deep enough to release part of the frozen reservoir of water lying beneath the surface.
(Image: © ESA/DLR/FU Berlin (G. Neukum))