Surface of Mars, artwork. Mars is a rocky desert world with no surface water. The atmosphere is mostly carbon dioxide and Martian surface temperatures are well below freezing. Mars has a diameter around half Earth's, and a surface gravity around a third that of Earth's. Mars orbits the Sun at a distance of around 230 million kilometres. Impact craters, sand dunes, mesas and canyons, and erosion features from wind and ancient water flows are depicted here.