The red planet, with the largest volcano and one of the longest canyons in the Solar System.
Mars is about half the size of Earth. Its red colour comes from iron oxide, rust, in the dust that covers its surface. It has a thin atmosphere of carbon dioxide and two small moons, Phobos and Deimos.
Giant landscapes
Mars has the largest volcano in the Solar System, Olympus Mons, more than twice as high as Mount Everest. The canyon system Valles Marineris, visible across the middle of the image above, is about 4,000 km long and up to 7 km deep.
Water on Mars
Dry river valleys and lake beds show that liquid water once flowed on Mars. Today water exists mainly as ice in the polar caps and below the surface. Rovers such as Curiosity and Perseverance search for signs that life may once have existed there.
The image above is a mosaic of 102 images taken by the Viking orbiters in the 1970s.