Courtesy EMSLMicrobes found living in rocks 1.5 miles under the ocean floor live such slow-paced lives that they reproduce only every 10,000 years or so. That's a long time between generations. They live this way in rocks estimated to be 100 million years old. The discovery was announced by scientists from the Integrated Ocean Drilling Program at a meeting of geochemists at the Goldschmidt onference in Florence, Italy. Scientists have also discovered other life forms - viruses and fungi - living zombie-like existences in the same deep rock layers.
Dr Beth Orcutt of Bigelow Laboratory for Ocean Sciences in Maine wonders how life exists in such extreme environments and where Earth's biosphere actually terminates.
"The deeper we look, the deeper we are still finding cells," she said, "and the discussion now is where is the limit? Is it going to be depth, is it going to be temperature? Where is the limit from there being life to there being no life?"
The density of the microbial population living in the deep rocks is miniscule compared to those found at the surface, but scientists still wonder if the microbes can actually be changing the lithosphere through chemical reaction with carbon and other elements in the rocks, and what results from that interaction.