Deep Carbon study finds science-fiction worlds deep underground
Earth is seen from the Apollo 8 spacecraft in December 1968. (NASA)
Published Monday, March 4, 2013 12:19PM EST
Turns out space isn't the only final frontier.
Scientists from 40 countries are boldly going deep, deep underground to study the movement of carbon kilometres below the Earth's surface. Early results from the historic 10-year, $500-million research project outline strange new worlds right out of science fiction: colonies of microbes millions of years old, hydrogen-eating life forms, natural gas seeping from chemical processes within the bedrock itself.
The discovery of vast reserves of buried carbon may suggest solutions to the climate change crisis on the surface. And the Earth's deepest recesses also suggest how life might behave on other planets.
"It is literally transforming our understanding of the planet and, through that, our understanding of other planets," said Barbara Sherwood Lollar, a University of Toronto scientist who's one of the directors of the Deep Carbon Observatory.
Deep Carbon, which released a book Monday outlining its initial findings, began as an attempt to balance the planet's carbon books.
Studies of meteorites suggest Earth was formed by material that was about three per cent carbon -- the one element that's essential to life. But carbon in surface rocks, the oceans and the atmosphere accounts for only a tiny fraction of that.
Where was the rest? And what was it doing?
What Deep Carbon has found -- so far -- is that unimaginably huge amounts of buried carbon have been involved in an intricate and stately dance with life since almost the beginning of the planet. As long as 3.8 billion years ago, biological processes were breaking down the young Earth's relatively uniform rock, concentrating their carbon and forming different rock types.
It's life itself that is responsible for much of the surface minerals that we see today.
"An old guessing game began: animal, vegetable or mineral?" said Robert Hazen, Deep Carbon's director. "We're learning now that for some types of rock the answer may be all three."
Nor does that buried carbon just sit there.
The slow drift of continental plates drives carbon-rich rocks from the surface deep underground. Eventually, that carbon comes back as erupting volcanoes belch carbon dioxide, linking the biological processes of the surface with the subterranean depths.
Those depths hold life of their own.
As far down as three kilometres, microbes exist in abundance despite the fact they take hundreds of thousands of years to reproduce. Viruses live there, too, swapping microbial DNA back and forth in what may have been life's first evolutionary lab.
Sherwood Lollar likens one microbe colony, found 2.8 kilometres underneath South Africa, to an underground Galapagos Island. It's been cut off from the surface for at least 10 million years.
"And yet, there is life," she said.
Some Deep Carbon researchers think those microbes live off hydrogen that is created when basalt from underwater lava flows react with sea water. The byproduct of that reaction is the bright green mineral serpentine, familiar to many Canadians through its use in Inuit carvings.
Similar water-rock processes deep underground also produce methane, or natural gas. Before, scientists thought methane was only produced by biological reactions or high-temperature, volcanic processes.
"It has majorly changed our understanding," said Sherwood Lollar.
Studying carbon deep beneath the surface could also pay off in attempts to get it out of the atmosphere, where it's the major cause of climate change, and store it back underground.
"There are places in the Earth where we know that the planet has been collecting CO2 over tens of millions of years," Sherwood Lollar said. "One of the things the carbon observatory can do is to use the naturally occurring processes of the Earth as a way of testing out some of the hypotheses that are being applied.
"Only the Earth can provide us with systems that already give us that kind of time scale."
Deep Carbon research also has implications for studying life beyond Earth. Sherwood Lollar said scientists now believe signs of life on planets such as Mars are more likely to be found below the surface.
"In some ways, the work that's being done on Earth is a test case for exploration of other planets."
Scientists involved in Deep Carbon are meeting this week in Washington, D.C., to discuss the project's findings.
"We're understanding our planet in a whole new way," said Hazen. "It's an adventure."