Water rich in methane and oxygen exists 2.4 kilometres below Earth's surface in a Canadian mine, remaining isolated for more than a billion years. The findings may hold clues about the origins of life on our planet and have implications for life on Mars.
While micrometer-scale crevices in minerals billions of years old can hold water that was trapped during the mineral formation, there has never been a shred of evidence of free-flowing water passing through interconnected cracks or pores in Earth's crust for tens of millions of years. The last time living microbes were discovered so deep was 2.8 kilometres below the surface in a South African gold mine, in fluids isolated from the photosphere tens of millions of years ago.
Chris Ballentine, a geochemist at the University of Manchester, UK, and colleagues report in Nature, the capture of water flowing through fractures in the 2.7-billion-year-old sulphide deposits in a copper and zinc mine near Timmins, Ontario. They have ensured that the water did not come into contact with mine air.
"We were expecting these fluids to be possibly tens, perhaps even hundreds of millions of years of age," says Ballentine in a news release.
Based on evidence involving the relative abundances of various isotopes of noble gases present in the water, the researchers determined that the fluid could not have contacted Earth's atmosphere 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. The area of the Canadian Precambrian Shield that the scientists probed shows that increased levels of "the isotopes 124Xe, 126Xe and 128Xe in the Timmins mine fluids can be linked to xenon isotope changes in the ancient atmosphere."
"The isotopic compositions that they see in these samples are extremely strange, and the preferred explanation in the article seems to me the most likely one," says Pete Burnard, a geochemist at the Centre of Petrographic and Geochemical Research in Vandœuvre-les-Nancy, France. "For the moment, I think we have to conclude that there are 1.5-billion-year-old fluids trapped in the crust."
"These are the oldest waters that have ever been identified," Barbara Sherwood Lollar, a geoscientist at the University of Toronto and one of the study's authors, told The Canadian Press. "We don't know yet if there's life in this, but what we've been able to show is it is habitable, meaning (having the) potential to support life because of the energy that's there."
The isolated water supply fluid carries the ingredients necessary to support life including secluded biomes, ecosystems, in which life might have even originated. Researchers are now investigating to establish whether the water does carry life.
The findings may also have implications for life on Mars since the surface of Mars has chemically similar rocks that once held water "There is no reason to think the same interconnected fluids systems do not exist there," speculated Ballentine.