Image: José Manuel Suárez via Wikimedia
Scientists have made an amazing discovery deep inside the Canadian Shield - one that goes back billions of years.
It's a reservoir of water located in a mine in Timmins, Ontario, that is the oldest free-flowing water ever found.
Canadian and British scientists say it's been trapped there for 1.5 billion to 2.64 billion years (back when oxygen breathing life first appeared on the planet), and hasn't come into contact with Earth's atmosphere since.
"It's exciting on about five different levels," said Barbara Sherwood Lollar, a professor of earth sciences at the University of Toronto who was involved in the discovery.
"It's like finding another world," she told The Globe & Mail.
It's believed the water was once on the surface, perhaps in an ocean that disappeared, and then seeped through the ground where it became trapped.
Scientists found it 2.4 kilometres underground in a copper and zinc mine. They say the water is rich in dissolved gases such as methane and hydrogen - two elements that support life, and in theory, could have helped some types of micro-organisms survive.
The team is now testing samples of the water to see if it contains any lifeforms - a process that could take several months.
As the BBC reports, if the water does have traces of life, it could help scientists understand the origins of life on Earth and "where it could exist underground today on other planets."
For example, the surface of Mars is cold and dry today, but billions of years ago, scientists believe it was much warmer and wetter. Some of that water is thought to have ended up in deep reservoirs.
"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 Greg Holland, a geochemist in Britain and 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."
The rock where the water was found is "very similar to Martian rocks," said Holland.
"When Mars was much more habitable, three or four billion years ago, maybe life there went underground and has carried on living happily ever since."
The scientists were able to estimate how long the water had been isolated, by analyzing the different types (or isotopes) of xenon gas that were dissolved in it.
They discovered an unusually high level of lighter xenon, which is thought to have come from the Earth's atmosphere a long, long time ago.
At one time, the atmosphere contained a lot of lighter xenon, but scientists believe it was destroyed by ultraviolet radiation and asteroids during the Earth's first few hundred million years.
The discovery involved researchers from the universities of Manchester and Lancaster in the U.K., and U of T, McMaster and the University of Alberta here in Canada.
It's published in this week's edition of the journal Nature.