One and a half miles beneath the surface of Earth in a Canadian mine, researchers have found pockets of water in rocks that have been isolated from the surface for some two billion years.
The chemistry of the water could support life, the team reports today in the journal Nature -- a tantalizing discovery that raises the possibility that life-supporting water might also lie in similar kinds of rocks deep beneath the surface of Mars.
Because the water was trapped at a time when Earth was very different than it is today, the new findings also lend insight into the evolution of the early atmosphere and the habitability of the deep Earth. Until now, the oldest known reservoirs of underground water dated back just tens of millions of years.
"For the first time, we found that waters of this age can be preserved on our planet," said Barbara Sherwood Lollar, an isotope geochemist at the University of Toronto. "Really, it's a whole new world, a whole new hydrosphere on our planet. We didn't know it was possible to trap this amount of fluid and gas for this kind of time scale."
Miners have long known that water sometimes flows out of fractures in rocks deep underground, Sherwood Lollar said. As scientists have more recently become interested in the phenomenon, they have discovered that these fluids are often very salty, with salinity levels 10 times higher than seawater.
Deep isolated waters also contain large amounts of dissolved hydrogen, making it possible that they might sustain microorganisms like the ones that live around hydrothermal vents. In 2006, in fact, Sherwood Lollar and colleagues found a community of microbes living deep below South Africa in isolated waters that were tens of millions of years old.
"I refer to hydrogen as the jelly donuts of the microbe world," Sherwood Lollar said. "If it's there, they want to eat it."