The water pouring out of boreholes 2.4 kilometres below the surface in the northern Ontario copper and zinc mine is older than any other free-flowing water ever discovered. It is rich in dissolved gases such as hydrogen and methane that could theoretically provide support for microbial life, the researchers report in a paper published Wednesday online in the journal Nature.
"What we can be sure of is that we have identified a way in which planets can create and preserve an environment friendly to microbial life for billions of years," said a statement from Greg Holland, the Lancaster University geochemist who is the lead author of the study.
"This is regardless of how inhospitable the surface might be, opening up the possibility of similar environments in the subsurface of Mars."
His Canadian co-authors included Barbara Sherwood Lollar and Georges Lacrampe-Couloume at the University of Toronto; Greg Slater at McMaster University in Hamilton; and Long Li, who is currently an assistant professor at the University of Alberta, but worked on the project while at the University of Toronto.
Some Canadian members of the team are currently testing the water to see if it contains microbial life — if they exist, those microbes may have been isolated from the sun and the Earth's surface for billions of years and may reveal how microbes evolve in isolation.
Microbes that have been isolated for tens of millions of years have been found in water with similar chemistry at even slightly deeper depths below the surface in a South African gold mine, using hydrogen gas as an energy source, the researchers noted.
The researchers estimated how old the water was based on an analysis of the xenon gas dissolved in it. Like many other elements, xenon comes in forms with different masses, known as isotopes. The water in the Timmins mine contained an unusually high level of lighter isotopes of xenon that are thought to have come from the Earth's atmosphere at the time it became trapped.
The Earth's atmosphere used to contain a lot more of the lighter xenon, but it is thought to have been destroyed by the high levels of ultraviolet radiation and the bombardment of asteroids on the surface of the Earth during the planet's first few hundred million years. Geological evidence from air trapped in ancient rocks has helped map the relationship between the amount of lighter xenon in the atmosphere and the age of the Earth at the time.
The study was funded by grants from the Natural Sciences and Engineering Research Council of Canada, the Canada Research Chairs program, the Natural Environment Research Council in the U.K., and the Deep Carbon Observatory.
Although the water found in the Timmins mine is older than any other known reservoir of flowing water, it is not the oldest water ever found. Water trapped inside tiny bubbles within rocks has been dated to be billions of years old. However, tiny droplets completely encased in rock can't support life.