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A pocket of water some 2.6 billion years old the most ancient pocket of water known by far, older even than the dawn of multicellular life has now been discovered in a mine 2 miles below the Earth's surface.

The finding, announced in the May 16 issue of the journal Nature, raises the tantalizing possibility that ancient life might be found deep underground not only within Earth, but in similar oases that may exist on Mars, the scientists who studied the water said.

Geoscientist Barbara Sherwood Lollar at the University of Toronto and her colleagues have investigated deep mines across the world since the 1980s. Water can flow into fractures in rocks and become isolated deep in the crust for many years, serving as a time capsule of what their environments were like at the time they were sealed off.

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In gold mines in South Africa 1.7 miles deep, the scientists previously discovered microbes could survive in pockets of water isolated for tens of millions of years. These reservoirs were many times saltier than seawater, "and had chemistry in many ways similar to hydrothermal vents on the bottom of the ocean, full of dissolved hydrogen and other chemicals capable of supporting life," Sherwood Lollar said. [Strangest Places Where Life Is Found on Earth]

To see what other ancient pockets of water might exist, Sherwood Lollar and her colleagues investigated copper and zinc mines near the city of Timmins in Ontario, Canada. "As the prices of copper, zinc and gold have gone up, mines now go deeper, which has helped our search for long-isolated reservoirs of water hidden underground," Sherwood Lollar said.

'Mind-blowing' find

"Sometimes we went down in cages they're not called elevators underground that dropped us to the levels we wanted to go," Sherwood Lollar told OurAmazingPlanet. "Other times, we went down ramp mines, which have curling spiral roadways, so we could actually drive all the way down."

The scientists analyzed water they found 2 miles deep. They focused on noble gases such as helium, neon, argon and xenon. Past studies analyzing bubbles of air trapped within ancient rocks found that these rare gases could occur in distinct ratios linked with certain eras of Earth's history. As such, by analyzing the ratios of noble gases seen in this water, the researchers could deduce the age of the water.

The scientists discovered the fluids were trapped in the rocks between 1.5 billion and 2.64 billion years ago.

"It was absolutely mind-blowing," Sherwood Lollar said. "These weren't tens of millions of years old like we might have expected, or even hundreds of millions of years old. They were billions of years old."

The site was formed by geological activity similar to that seen in hydrothermal vents. "We walked along what used to be ocean floor 2.7 billion years ago," Sherwood Lollar said. "You could still see some of the same pillow lava structures now seen on the bottom of the ocean."

Signs of life?

This ancient water poured out of the boreholes the team drilled in the mine at the rate of nearly a half-gallon (2 liters) per minute. It remains uncertain precisely how large this reservoir of water is.

"This is an extremely important question and one that we want to pursue in our future work," Sherwood Lollar said. "We also want to see if there are habitable reservoirs of similar age around the world."

Sherwood Lollar emphasized they have not yet found any signs of life in the water from Timmins. "We're working on that right now," she said. "It'd be fascinating to us if we did, since it'd push back the frontiers of how long life could survive in isolation."

And the implications of such a finding would extend beyond the extremes of life on Earth.

"Finding life in this energy-rich water is especially exciting if one thinks of Mars, where there might be water of similar age and mineralogy under the surface," Sherwood Lollar said.

If any life once arose on Mars billions of years ago as it did on Earth, "then it is likely in the subsurface," Sherwood Lollar said. "If we find the water in Timmins can support life, maybe the same might hold true for Mars as well."

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