In March, NASA scientists reported that the rover Opportunity had uncovered evidence that there was once water on Mars—significantly upping the chances that life, too, once existed on the Red Planet. In response, the London bookmaker Ladbrokes halted its decades-old practice of accepting wagers on whether evidence of Martian life would be discovered. A look back at how the Mars "action" has shifted.

1,000 to one Early 1960s: a London bookmaker accepts the £10 bet of one David Threlfall that man will walk on the Moon before the end of the decade. When Neil Armstrong does so, on July 20, 1969, Threlfall collects £10,000. Shortly after the Moon walk bookmakers begin taking wagers on the discovery of past Martian life.

50 to one August 7, 1996: NASA scientists announce that a Martian meteorite found in Antarctica contains traces of what appear to be cellular fossils. The evidence is inconclusive. Nevertheless, Ladbrokes cuts the odds.

33 to one September 30, 1998: Betting increases as the Mars Global Surveyor descends to a closer orbit of the Red Planet, with the expectation of more-detailed data. Ladbrokes cuts the odds.

25 to one December 23, 2003: After heavy betting anticipating the touchdown of the Beagle 2, the Mars Express lander, Ladbrokes cuts the odds. The Beagle 2 is lost, but the odds remain unchanged.

16 to one January 15, 2004: Ladbrokes becomes worried about its exposure on the Mars bets and cuts the odds.

Bets off March 3, 2004: The day after NASA announces that the Opportunity has found evidence that Mars was once "soaking wet," Ladbrokes stops taking bets.