Scientists have found bacteria living almost three kilometers underground that are completely independent of the sun. They basically survive on water plus rocks plus radiation.
Found in water spilling out of a fissure in a South African goldmine in 2003, they are among the most primitive life forms described, researchers reported in yesterday's issue of the journal Science.
What is unusual is that their underground home contains no nutrients traceable to photosynthesis, the sunlight-harnessing process that fuels all life on earth's surface. Such a community is an oddity on this planet - and is of interest to people looking for life on other ones.
"There is an organism that dominates that environment by feeding off an essentially inexhaustible source of energy, radiation," said Tullis Onstott, a geoscientist at Princeton University who led the team.