The ancient water contains chemicals that could support life without sunlight.
Pockets of water trapped in rocks from a
Canadian mine are over a billion years old, and the water could contain
life forms that can survive independently from the sun.
The ancient water was collected
from boreholes at Timmins Mine beneath Ontario, Canada, at a depth of
about 1.5 miles (2.4 kilometers).
"When these rocks formed, this part of Canada was the ocean floor," said study co-author Barbara Sherwood Lollar, an Earth scientist at Canada's University of Toronto.
"When we go down [into the mine] with students, we like to say imagine you're walking on the seafloor 2.6 billion years ago."
Working with U.K. colleagues Chris Ballentine and Greg Holland,
Sherwood Lollar and her team found that the water was rich in dissolved
gases such as hydrogen and methane, which could provide energy for
microbes like those found around hydrothermal vents in the deep ocean.
In
addition, the water contained different rare gases that include the
elements helium, neon,
argon, and xenon, which were created through interactions with the surrounding radioactive rock. By measuring the concentrations of isotopes of these "noble gases"—so called because they rarely interact with other elements—the team could estimate how long the water had been trapped underground and whether it had been isolated.
argon, and xenon, which were created through interactions with the surrounding radioactive rock. By measuring the concentrations of isotopes of these "noble gases"—so called because they rarely interact with other elements—the team could estimate how long the water had been trapped underground and whether it had been isolated.
Depending
on the noble gas analyzed, the age estimates for the water varied
between 1.1 billion years old and 2.6 billion years old—or as old as the
rocks in the mine itself.
"It shows us that there's
been very little mixing between this water and the surface water,"
Sherwood Lollar said. "What we want to do with further work is see if we
can narrow that [age range] down."
Teeming With Life?
Geologists
have long known that a lot of water can be present in continental
crust, locked away in microscopic voids in minerals, pore spaces between
minerals, and veins and fractures in the rock. But what's been unclear
is the age of such water, said geochemist Steven Shirey, a senior scientist at the Carnegie Institution for Science.
"The
question is how old is it? Is it water that's part of current
circulation with surface water? Or is it water that retains old
chemistry and potential biota?" said Shirey, who was not involved in the
study.
The new findings, detailed in May 2013 issue of the journal Nature, is evidence that ancient pockets of water can remain isolated in the Earth's crust for billions of years.
"That's the really exciting part about this study," Shirey said.
Sherwood
Lollar and her team are testing the mine water to see if they can find
evidence of living microbes. If life does exist in the water, she said,
it could be similar to microbes previously found in far younger water
flowing from a mine located 1.74 miles (2.8 kilometers) beneath South
Africa.
Those microbes could survive without light from
the sun, subsisting instead on chemicals created through the
interactions between water and rock.
Such "buried" microbial communities are rare, and fascinating for scientists because they are often not interconnected.
"Each
one of them may have a different age and a different history," Sherwood
Lollar said. "It will be fascinating for us to look at the microbiology
in each of them ... It'll tell us something about the evolution of life
and the colonization of the subsurface."
Expanding Horizons
The
Timmins Mine water could also help scientists understand how much of
the subsurface of the Earth is actually inhabited by life. The answer to
that question has implications for life on other planets, such as Mars,
scientists say.
"It opens up your horizons for what's
possible," Shirey said. "If you think that you can have microbial life
throughout the entire crust of the Earth, then all of a sudden it
becomes very possible that life could live on other planets under the
right condition."
That raises questions about potential
life in relatively warm rock located beneath the cold surface of Mars,
where liquid water could still exist.
"We're looking at
billion-year-old rock here and we can still find flowing water that's
full of the kind of energy that can support life," Sherwood Lollar said.
"If
we find Martian rocks of the same age and in places of similar geology
and mineralogy to our site, then there's every reason to think that we
might be able to find the same thing in the deep subsurface of Mars."
- Ker Than (National Geographic)
