Surface of Mercury. Computer illustration of a view across the rocky surface of the planet Mercury, with the Sun (top left) on the horizon. Mercury is the closest planet to the Sun, orbiting at an average distance of 58 million kilometres, less than half the Earth-Sun distance. The solar wind blasts atoms from its rocky surface, forming a very thin atmosphere that is constantly lost to space. The surface temperature extremes are the greatest in the solar system, ranging from 400 to minus 170 degrees Celsius.