A remote expedition to the deepest layer of the Earth's oceanic crust has revealed a new ecosystem living over a kilometer deep. Analysis of this new biosphere suggests life could exist lower still.
To facilitate the task, the Integrated Ocean Drilling Programme led by Stephen Giovannoni of Oregon State University drilled down to 1391 meters through sediment and a layer of basalt, to hit the gabbroic layer, which lies directly above the mantle on the Atlantis Massif. Tectonic activity beneath this submerged mountain in the central Atlantic Ocean has pushed the gabbroic layer within 70 metres of the sea floor, where temperatures reach 102 °C.
At the gabbroic layer the researchers found communities of bacteria that were sparse but widespread. The type of bacteria they found came as a surprise to Giovannoni, who has previously found micro-organisms living in the basalt layer. "We expected to find similar organisms in the deeper layer," he reported to New Scientist. "But actually it was very different."
One key finding was that many of the gabbroic bugs had evolved to feed off hydrocarbons like methane and benzene, similar to the bacteria found in oil reservoirs and contaminated soil, which could mean that the bacteria migrated down from shallower regions rather than evolving inside the crust.
In an earlier 2005 expedition, Giovannoni and colleagues discovered that the smallest free-living cell known also has the smallest genome, or genetic structure, of any independent cell - and yet it dominates life in the oceans, thrives where most other cells would die, and plays a huge role in the cycling of carbon on Earth. In nature, bigger is not always better.
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http://www.dailygalaxy.com/my_weblog/2010/11/extreme-life-is-found-in-deepest-layer-of-earths-crust-living-on-methane-and-benzene-bacteria-thrivi.html
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