BOOKMAKERS have stopped taking bets on signs that life once existed on Mars, after Nasa found evidence that the red planet had a wet climate.

Nasa scientists claimed to have "strong evidence" that "at least one part of Mars had a persistently wet environment that could possibly have been hospitable to life".

Ladbrokes said punters who may have placed bets in the 1970s at odds of 1,000/1 would cost bookies a fortune if proof of Martian life forms were found.

Warren Lush, a spokesman for Ladbrokes said: "Following the latest news from Nasa we think it is now likely that evidence of past life on Mars will be found in the coming years."

The odds on past life on Mars were 16/1 when the book was closed.

Punters who still fancy a flutter, are being offered the chance to place a bet on existing extraterrestrial life.

The Opportunity rover probe, which landed on Mars five weeks ago, has been studying the composition of rocks, which Nasa said showed they were once covered by flowing water.

Opportunity landed near an exposed bedrock embedded in the wall of a small crater.

The rover conducted a chemical analysis of the outcrop, including a rock named El Capitan by scientists, and found a concentration of sulphur, rich in magnesium and iron.

Opportunity's instrument also detected jarosite, an iron sulphate mineral.

On Earth, such minerals would have formed in water and the presence of jarosite suggests an acid-rich lake or hot springs environment, scientists said.