It's one small step for a bug, a giant red face for Nasa - World - Times Online: "FAR from discovering life on Mars, Nasa may have put it there. The American space agency believes the two rover spacecraft scuttling across the red planet are carrying bacteria from Earth, writes John Harlow.
The bacteria, bacillus safensis, were found in a chamber in California that had been used to test the rovers. Officials believe it is likely some of the microbes, possibly from scientists’ skin, were on board when the mission left."