It’s older than cavemen. It predates the dinosaurs. And it just might contain clues to the possibility of life on Mars.

A team of U.K.-Canadian scientists have discovered billion-year-old water deep underground in an Ontario mine and, according to their research published in the journal Nature on Wednesday, they think it might actually contain life.

“We've found an interconnected fluid system in the deep Canadian crystalline basement that is billions of years old, and capable of supporting life,” University of Manchester professor Chris Ballentine said in a news release. “Our finding is of huge interest to researchers who want to understand how microbes evolve in isolation, and is central to the whole question of the origin of life, the sustainability of life, and life in extreme environments and on other planets.”

Researchers from the universities of Manchester, Lancaster, Toronto and McMaster analyzed water pouring out of boreholes 2.4 kilometres underground near Timmins, Ontario.

The water contains a nourishing cocktail of gases – like hydrogen, methane and different forms of noble gases – that could sustain microbes that haven’t seen sunlight for billions of years.

Mars is dominated by similar geologic terrain, which leads researchers to ask one very big question: does life exist on Mars deep below the surface too?

“Our Canadian colleagues are trying to find out if the water contains life right now,” Lancaster University lecturer Greg Holland said in a statement. “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.

“This is regardless of how inhospitable the surface might be, opening up the possibility of similar environments in the subsurface of Mars.”

Billion-year-old water has been discovered in the past but only trapped in tiny bubbles in rock and never capable of supporting life, according to the researchers.