Vesta gullies look 'water cut'
7 December 2012 Last updated at 07:00 GMT
Scientists say they have seen features on Asteroid Vesta that look as though they could have been cut by some sort of fluid flow - possibly liquid water.
The gullies, seen running down the walls of some craters, were pictured by Nasa's Dawn probe.
Dawn's principal investigator Christopher Russell spoke to our correspondent Jonathan Amos.