FLORIDA, Dec. 11 – Scientists have drilled 2.5 kilometers below the seabed and found vast underground forests of "deep life," including microbes that persist for thousands, perhaps millions of years, researchers said yesterday.
Feeding on nothing but the energy from rocks, and in a slow-motion, even a zombie-like state, previously unknown forms of life are abundant beneath Earth despite extreme temperatures and pressures.
About 70 percent of Earth's bacteria and archaea – live underground, according to the latest findings of an international collaboration involving hundreds of experts known as the Deep Carbon Observatory, were released at the American Geophysical Union meeting in Washington.
This "deep life" amounts to between 15 and 23 billion tonnes of carbon, said DCO, launched in 2009, as it nears the end of its 10-year mission to reveal Earth's internal secrets.
"The deep biosphere of Earth is massive," said Rick Colwell, who teaches astrobiology and oceanography at Oregon State University.
He described the team's findings so far as "a very exciting, extreme ecosystem."
Among them may be Earth's hottest living creature, Geogemma barossii, and a single-celled organism found in hydrothermal vents on the seafloor.
Its microscopic cells grow and replicate at 121 degrees Celsius.
"There is a genetic diversity of life below the surface that is at least equal to but probably exceeds that which is at the surface and we do not know much about it," Colwell said.
'Distinct' from surface life
Similar types of strange, deep-life microbes can be found on the underground of other planets like Mars.
"Most of the deep life is very distinct from life on the surface," said Fumio Inagaki, of the Japan Agency for Marine Earth Science and Technology.
Using the Japanese scientific vessel Chikyu, researchers have drilled far below the seabed and removed cores that have given scientists a detailed look at deep life.
"The microbes are just sitting there and live for very, very long periods of time," he told AFP.
The researchers have seen some microbes, bacteria and fungi slowly waking up.
"That was amazing," Inagaki said.
Scientists have found life in continental mines and boreholes more than five kilometers deep, and have not yet identified the boundary where life no longer exists, he added.
How does basic biology work?
Gaining a better understanding of subsurface life on Earth can also help understand and better engineer climate-change fighting technologies that may one day sequester carbon from the atmosphere.
"What we learn here will help us understand what to look for on other planets or other systems where life could exist," said Colwell.
In any case, studying what some scientists call the "Galapagos of the Deep" dramatically changes the human perception of life on Earth and their place in it.
Most of our planet's microbial life is deep beneath the surface, and it may have played a big part in the evolution of Earth's atmosphere by locking carbon dioxide underground and allowing air for people and animals to breathe.
"There's lots and lots of life on Earth that we did not know about. The fact that so much of it – at least in the marine sediment – is functioning at extremely low energy, it really changes our basic concept of how biology works, "said Karen Lloyd, associate professor at the University of Tennessee at Knoxville.
"They are new branches on the tree of life that have been on Earth, doing whatever they are doing, for billions of years, but without us ever noticing them," she told AFP.
"It's like looking outside you and finding that you have an officer you never knew about." – AFP