Mercury is the smallest planet in our solar system and closest to (our) Sun. Its surface is pockmarked with craters of varying size, resulting from what we assume was a heavy dose of asteroids, comets and other space matter crashing into it. This picture was taken by the Messenger space probe which has been studying Mercury for over ten years. At the bottom right of this picture is the Alver crater, while the 760 kilometer long Belgica Rupes region can be seen at the top.