Martian gullies 'carved by water'

Interesting photographs of terrain features on the Martian surface have now been said to possibly be the result of water runoff. Several theories as to how the water became present there exist, ranging from snow melt and rain to the possibility that it arrived at the surface from a subterranean source and was able to run down these gullies, causing erosion patterns, before being evaporated or frozen. This evidence relies heavily on the wobble theory which suggests that the planet changes it angle along its axis, resulting in drastic changes in the ice coverage on the Martian surface. These images, coming from the MGS, are some of the most recent examples of evidence showing the possible presence of liquid water on the surface of Mars within the last few thousand years.

http://news.bbc.co.uk/2/hi/science/nature/2781699.stm