May 23, 2008

Living Microbes Found a Mile Below Seabed

Scientists have been given a hint that life might evolve underground on other planets as microbes were discovered living at a record depth of one mile beneath the Atlantic seabed.

Experts in Wales and France noted that the discovery of prokaryotic microbes in searing hot sediments under the seabed off Newfoundland, Canada, doubles the previous depth record of 842 meters.

"This is the deepest, oldest and hottest marine sediments that prokaryotic life has been found in," said John Parks, co-author and professor at the University of Wales.

The report said the microbes were found at 1,626 meters below the seafloor in sediments 111 million years old and at temperatures of 60 to 100 degrees Celsius (140-212.00 Fahrenheit).

Prokaryotes are microbes lacking nuclei, comprising archaea and some types of bacteria. The lack of cell nuclei distinguishes them from eukayrotes, or all animal and plant life.

Parks said if there is a substantial subsurface biosphere on earth there could also be substantial biospheres on other planets. He estimates that such microbes could survive temperatures down to about 4 km below the seabed on earth.

"Just taking a scoop from the surface of Mars is not going to tell you whether there is life on Mars or not," he said.

It is not clear whether the microbes off Newfoundland had any connection to the sun's energy, which is the source of life at the surface. They might eat buried methane, for instance, formed by compressed plants millions of years ago.

It is possible they might be independent of the sun and depend on geochemical energy, like some life forms around volcanic vents on the floors of the oceans. On land, life has also been found deep in mines.

These finding could upset plans by many nations and companies to bury greenhouse gases from fossil-fuelled power plants or factories in porous rocks deep below the seabed where it was long thought to be devoid of life.

"It's a very risky prospect just putting gases into geological formations and not considering there could be a feedback response because of the organisms down there," Parks said.

Parks said more assessment was needed to determine how microbes might react with carbon dioxide. The London Convention, which governs dumping at sea, was amended last year to permit storage of carbon dioxide in seabed sediments.

Burial of carbon dioxide could be one of the main tools this century to slow global warming that could bring more floods, droughts and rising seas, according to the U.N. Climate Panel.