NASA 'put' life on Mars

Far from discovering life on Mars, NASA may have put it there.

The US space agency believes the two rover spacecraft scuttling across the red planet are carrying bacteria from Earth.

The bacteria, bacillus safensis, were found in a chamber in California that had been used to test the rovers. Officials believe it is likely that some of the microbes, possibly from scientists' skin, were on board when the mission left.

The craft, Spirit and Opportunity, landed on Mars last year. One key task was to look for signs of life: now it seems that if there are any organisms, it is man who has put them there. If proved, the contamination would raise concerns at possible breaches of a UN treaty to stop other planets being polluted from Earth.

The claims have been made by Kasthuri Venkateswaran, a microbiologist at NASA's spacecraft assembly plant in Pasadena. His tests have shown the microbes could survive space travel and Mars's -60C climate.

It is believed the bacteria are living inside the electronic circuitry of the two landers. The error is revealed in Out of Eden, by Alan Burdick. A NASA spokesman said there were "massive odds" against the microbes becoming established on the planet.