Scientists have discovered an ancient pocket of water trapped deep beneath the ground which could have been isolated from the rest of the world for up to 2.7 billion years – making it the oldest known aquifer, with scientists wondering whether it contains life.

The water was found pouring out of boreholes from a copper and zinc mine 2.4 kilometres deep beneath Ontario in Canada. Chemical analysis shows that the water could support primitive microbial life-forms if they were adapted to living off the minerals and hydrogen seeping into the water from the surrounding rock.

Tests by researchers have shown that the water is at least 1.5 billion years old, but the surrounding geology suggests it could be much older, dating to a time when all of life on Earth had not evolved much beyond primitive, single-celled microbes.

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The scientists said they intend to analyse the water for signs of life, which could help in the development of techniques for finding extra-terrestrial life-forms living within underground pockets of water on either Mars or Europa, one of the moons of Jupiter.

“We’ve found an interconnected fluid system in the deep Canadian crystalline basement that is billions of years old, and capable of supporting life,” said Professor Chris Ballentine of the University of Manchester, a co-author of the Anglo-Canadian study published in the journal Nature.

“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,” Professor Ballentine said.

The water has a similar composition of dissolved chemicals to much young water found flowing from rock in a South African mine some 2.8km below ground where microbes have been found to live, the scientists said.

Any life-forms found in the water must be able to survive in total darkness on chemical energy locked up in the ancient rock formation. Scientists have begun tests to analyse the water for any microbes that have survived the long isolation from the rest of the biosphere, said Greg Holland of Lancaster University.

“Our Canadian colleagues are trying to find out if the water contains life right now. What we can be sure of is that we have identified a way in which planets can create and preserve and environment friendly to microbial life for billions of years,” Dr Holland said.

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

Living organisms that can survive in extreme environments – known as extremophiles – have been found in sediments retrieved from deep boreholes, in boiling hot geysers, highly radioactive habitats, deep submarine trenches and the dry, freezing deserts of Antarctica.