MARS had running water on its surface less than a million years ago, new evidence has suggested.
The discovery increases the chances of life existing on the planet in the recent past – or even surviving today.
American scientists have identified fan-like gullies inside a crater that appear to be not more than 1.25 million years old. They beli
eve the channels must have been sculpted by surface water from melting ice.
There is evidence of water-borne sediments being carried down from high ground and deposited in low-lying alluvial fans.
Professor James Head, from Brown University in Providence, Rhode Island, said: "We think there was recent water on Mars. This is a big step in the direction to proving that."
The gully system is in Promethal Terra, an area of cratered highlands south of the Martian equator.
A powerful camera on the United States space agency Nasa's Mars Reconnaissance Orbiter spacecraft was able to distinguish four individual lobes of deposited material in the fan system.
One was pockmarked with small craters linked to a rayed crater some 80 kilometres away that is known to be 1.25 million years old.
This lobe was likely to be about the same age. The other three lobes were unblemished and therefore had to be younger, the scientists said after their study, which was reported in the journal Geology.
They believe the best explanation for the gullies is melting snow and ice, rather than ground water bubbling up to the surface.
The finding follows the discoveries of water-bearing minerals such as opals and carbonates on Mars. Experts now think the planet was occasionally wet for far longer than was previously believed.
Meanwhile, scientists said an unexplored lake "frozen in time" for hundreds of thousands of years beneath Antarctica could contain "unique forms of life" that give clues to life on Mars.
Experts have been given the go-ahead to explore the ancient lake, described as "one of the planet's last great frontiers".
Buried under three kilometres of ice, the lake, which is the size of Windermere, in the Lake District, has been sealed from the outside world until now, and it likely to be home to unknown, unspoiled life forms.
The team hopes the exploration of the waters, which have been shielded from the world's pollution by the aged ice sheet, will yield vital clues about climate change, future sea-level rise and even the nature of life on Mars.
Professor Martyn Tranter, from Bristol University, will be analysing some of the water from the lake. He said: "
If we find anything living beneath the ice, it will not only be very exciting in itself but could have implications for life in similar icy environments, such as on other planets."
Cherry Lewis, of Bristol University, said: "It is frozen in time. When we talk about life on other planets, we're talking about mainly micro-organisms, and primarily about the planet Mars.
"It is possible we will find higher life forms down there. It's a complete unknown, which is why it is so exciting."
David Blake, who is head of technology and engineering at the British Antarctic Survey, said: "This project is a great scientific challenge and the technology required to drill 3km through the ice without contaminating the lake is equally ambitious."
