Candidatus Desulforudis audaxviator is a bacterium that has evolved to live and proliferate without sunlight, relying on mineral food sources that result from radioactive decay of minerals in the surrounding rock for energy.
It was initially found in water-filled cracks in the ground 2 miles underground in South Africa.
But the Census of Deep Life found a sample with 99 percent identical DNA in boreholes 3,000 feet beneath the surface near Death Valley, Calif.
Researchers say D. audaxviator probably started out as a more traditional life form, but evolved to live deeper. It could have spread around the world in underground water flows.
Another theory has it being brought to the surface in springs, then carried by the wind or in storms across a wide area, where it once again sank to great depths.
Its discovery was announced at the American Geophysical Union conference in San Francisco.
Photo: NASA Astrobiology