Of course there is, water falls out of the sky as meteors all the time on all planets.

12 March 2013 Last updated at 17:19

Mars rover Curiosity sees key water indicator
By Jonathan Amos

Science correspondent, BBC News
The rover collected about a tablespoon of powder from the drill hole Continue reading the main story

The US space agency (Nasa) has reported that its Curiosity rover has made another significant discovery on Mars. The robot has drilled into a rock that contains clay minerals - an indication of formation in, or substantial alteration by, neutral water. Scientists say the find is one more step towards showing conditions on the Red Planet in the distant past could have supported life.Many rocks studied previously were probably deposited in acidic water. While this would not have precluded the possibility of micro- organisms taking hold on Mars, it would have been more challenging, scientists believe. Identifying clays shows there were at least some locations on the planet billions of years ago where environments would have been much more favourable.

"We have found a habitable environment that is so benign and supportive of life that probably if this water was around and you had been there, you would have been able to drink it," said John Grotzinger, Curiosity's project scientist.The rover made the assessment after studying a powdered sample drilled from a fine-grained mudstone at its exploration site in Gale Crater, a deep impact bowl on Mars' equator.

Curiosity pictured at its drill site in Yellowknife Bay. The sampled mudstone lies just in front It found the rock sample to contain 20-30% smectite - a particular group of clay minerals. This high abundance and the lack of salt are strongly suggestive of a fresh-water environment. The presence of calcium sulphates, rather than magnesium or iron sulphates seen in those previous rocks, adds to the evidence that the sampled rock formed in a neutral to mildly alkaline pH environment. Scientists think Curiosity probably drilled into an ancient lakebed.The analysis also identified sulphur, nitrogen, hydrogen, oxygen, phosphorus and carbon - some of the key chemical elements for life. Additionally, it found compounds in a range of oxidised states, meaning there were electrons moving through the environment. Those could have been co-opted as an energy source by simple life-forms, if they were present.The rover is building quite a catalogue of evidence for ancient water at Gale. Already, it has revealed the remains of an ancient riverbed system, where water once flowed perhaps a metre deep and quite vigorously.The robot is currently working a small depression known as Yellowknife Bay, about half a kilometre from its touchdown site last August. Nasa's original mission plan was to head towards the big mountain that dominates the centre of Gale Crater, but the fascinating science at Yellowknife means this journey has been delayed. Researchers on the project intend now to remain at the present location for several weeks before beginning the long drive to Mount Sharp. Satellite images indicate clay minerals will also be found at the base of the mountain.