Scientists working 2.4 kilometers below Earth’s surface in a Canadian mine have tapped a source of water that has remained isolated for at least a billion years. The researchers say they do not yet know whether anything has been living in it all this time, but the water contains high levels of methane and hydrogen — the right stuff to support life.
Micrometer-scale pockets in minerals billions of years old can hold water that was trapped during the minerals’ formation. But no source of free-flowing water passing through interconnected cracks or pores in Earth’s crust has previously been shown to have stayed isolated for more than tens of millions of years.
“We were expecting these fluids to be possibly tens, perhaps even hundreds of millions of years of age,” says Chris Ballentine, a geochemist at the University of Manchester, UK. He and his team carefully captured water flowing through fractures in the 2.7-billion-year-old sulphide deposits in a copper and zinc mine near Timmins, Ontario, ensuring that the water did not come into contact with mine air.
To date the water, the team used three lines of evidence, all based on the relative abundances of various isotopes of noble gases present in the water. The authors determined that the fluid could not have contacted Earth’s atmosphere — and so been at the planet’s surface — for at least 1 billion years, and possibly for as long as 2.64 billion years, not long after the rocks it flows through formed.
Teeming With Life?
Geologists have long known that a lot of water can be present in continental crust, locked away in microscopic voids in minerals, pore spaces between minerals, and veins and fractures in the rock. But what’s been unclear is the age of such water, said geochemist Steven Shirey, a senior scientist at the Carnegie Institution for Science.
“The question is how old is it? Is it water that’s part of current circulation with surface water? Or is it water that retains old chemistry and potential biota?” said Shirey, who was not involved in the study.
The new findings, detailed in this week’s issue of the journal Nature, is evidence that ancient pockets of water can remain isolated in the Earth’s crust for billions of years.
“That’s the really exciting part about this study,” Shirey said.
Sherwood Lollar and her team are testing the mine water to see if they can find evidence of living microbes. If life does exist in the water, she said, it could be similar to microbes previously found in far younger water flowing from a mine located 1.74 miles (2.8 kilometers) beneath South Africa.
Those microbes could survive without light from the sun, subsisting instead on chemicals created through the interactions between water and rock.
Such “buried” microbial communities are rare, and fascinating for scientists because they are often not interconnected.
“Each one of them may have a different age and a different history,” Sherwood Lollar said. “It will be fascinating for us to look at the microbiology in each of them … It’ll tell us something about the evolution of life and the colonization of the subsurface.”
The Timmins Mine water could also help scientists understand how much of the subsurface of the Earth is actually inhabited by life. The answer to that question has implications for life on other planets, such as Mars, scientists say.
“It opens up your horizons for what’s possible,” Shirey said. “If you think that you can have microbial life throughout the entire crust of the Earth, then all of a sudden it becomes very possible that life could live on other planets under the right condition.”
That raises questions about potential life in relatively warm rock located beneath the cold surface of Mars, where liquid water could still exist.
“We’re looking at billion-year-old rock here and we can still find flowing water that’s full of the kind of energy that can support life,” Sherwood Lollar said.
“If we find Martian rocks of the same age and in places of similar geology and mineralogy to our site, then there’s every reason to think that we might be able to find the same thing in the deep subsurface of Mars.”