Nature

Organism Found Living at Extreme Depths beneath Seafloor: 1.6 Kilometers

Hottest life form ever discovered lives at temperatures up to 100 Celsius

By Gabriel Gache, Science News Editor

26th of May 2008, 15:19 GMT

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Life forms with similar characteristics to those of prokaryotes live inside hydrothermal springs in Yellowstone National Park

The previous greatest depth under the surface of the seafloor at which life was found is about two times less than that of the current record of 1.6 kilometers, thus encouraging future life searches on other planets in the solar system. The newly found microscopic life is also believed to be one of the hottest ever discovered, since it is living at temperatures ranging between 60 to 100 degrees Celsius.

The evidence comes from sediment seafloor samples collected

from the North Atlantic Ocean, that were studied by R. John Parkes from the Cardiff University, who has proven that they contain microbial life forms known as prokaryotes, having characteristics similar to those of extremophiles species common to hot springs such as those found in the Yellowstone National Park in the US. They appear to be feeding on methane and hydrocarbons created by the heat coming from the inner regions of the planet while interacting with organic material contained in the sediments. "That's what we think they're using as an energy source," Parkes said.

If Parkes is correct and these microbes are not just trapped in the sediments of the ocean floor, then more than 70 percent of the prokaryotes could live inside sediments up to a couple of kilometers thick. Alternatively, prokaryotes could make up 10 to 30 percent of the total mass of living matter on Earth. Parkes also believes that this proves once again that our view of life as being surface centric oriented is wrong, and that even planets with extreme conditions on the surface may contain life deep underground.

"There are nonbiological sources that can produce methane and related chemicals. Therefore, there might be a biosphere on other planets that may not require" sunlight or other surface resources, Parkes explained. "The more places we look for life, the more places we find it. This new study furthers the notion that the days of limiting our search for new life to surface conditions are long gone. The findings of this work push the limits in terms of both pressure and temperature," said Dennis Geist, from the University of Idaho, in a critical reply regarding Parkes' study.

Giest also pointed out that sample extraction began at a depth of 4.5 kilometers beneath the surface of the water, where temperatures draw near to freezing, and stopped at a depth of 1.6 kilometers beneath the surface of the ocean floor, having temperatures near the boiling point of water. The conditions are too extreme, Geist concluded.

TAGS:

seafloor | life | prokaryotes | methane | sunlight

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