Life-forms have been found thriving a mile (1.6 kilometers) beneath the seafloor in hot sediments, a new study says.
The finding doubles the maximum known depth for organisms under the ocean bottom—and may be an encouraging sign for the search for life on other planets.
At 140 to 212 degrees Fahrenheit (60 to 100 degrees Celsius), the microscopic life forms are probably also the hottest life-forms yet found in seafloor sediments, according to study co-author R. John Parkes, a microbiologist at Cardiff University in the United Kingdom.
(Related: "Hottest Life-Form Found: Microbe Thrives When Boiling" [May 21, 2004].)
The scientists examined core samples of sediments in the North Atlantic Ocean and found microbes known as prokaryotes.
Many of the prokaryotes share characteristics in common with "extremophiles," which live in hot springs, both under the sea and in areas such as Yellowstone National Park.
The microbes appear to make their livings by metabolizing methane and other hydrocarbons created as the Earth's interior heat warms organic material in the sediments, Parkes said.
"That's what we think they're using as an energy source."
The organisms do not appear simply to have been dormant microbes trapped in the sediments, Parkes added, but instead appeared to be thriving.
The discovery supports predictions that as much as 70 percent of the Earth's prokaryotes may live in seabed sediments, some of which can be several miles thick.
All told, Parkes said, these prokaryotes could amount to 10 to 30 percent of the world's total living matter.
Life on Mars?
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