Uranus' moon Oberon, Voyager 2 image. This composite colour image of Oberon, Uranus' outermost moon, was taken on the 24th January 1986 from a distance of 660,000 kilometres. Clearly visible are several large impact craters in Oberon's icy surface, surrounded by bright rays. In the centre of this image is a large crater with a bright central peak and a floor partially covered with very dark material. This may be icy, carbon-rich material erupted onto the crater floor sometime after it had formed. Another striking topographical feature is a large mountain about 6 kilometres high seen on the rim of the moon (bottom left). Voyager 2 was a space probe sent to image the outer solar system. It was launched on 20th August 1977.