Evidence for liquid water on Mars. Satellite image of a branching area (white, centre), on the wall of a Martian crater, where surface material has shifted and moved. The movement occurred some time between August 1999 and February 2004, and it is thought that it was caused by fluid transport, possibly underground liquid water. The feature seen here is several hundred metres long. The crater is in the Centauri Montes region of Mars. This image was obtained in September 2005, using several sensors carried onboard the Mars Global Surveyor spacecraft that is in orbit around Mars.