The discovery that billion-year-old water collected from a Timmins, Ont. mine has the right chemistry to support life could have important implications for the habitability of other planets.

Barbara Sherwood Lollar holds the Canada Research Chair in Isotope Geochemistry of the Earth and the Environment at the University of Toronto. Sherwood Lollar has been studying the composition of the salty fluids trapped in deep rock fractures, which are often encountered by miners, for decades. “In most parts of the planet, penetration by surface waters has diluted out ancient fluids,” says Sherwood Lollar, adding that tiny, isolated drops can be extracted from mineral inclusions. What makes samples from Timmins unique is that they are both pristine and of significant volume, which allows a whole suite of analytical techniques to be employed.

In a paper published in Nature, Sherwood Lollar’s collaborators Chris Ballentine and Greg Holland of University of Manchester measured the levels of various noble gas isotopes, produced via radioactive particles. The radiogenic isotopes accumulate in the water and provide an estimate of how long the water has been buried. Results showed that the fluids had been trapped for between 1.5 and 2.6 billion years, almost as old as the rocks themselves. Moreover, Sherwood Lollar’s team showed that the fluids were rich in hydrogen, a key substrate for anaerobic bacteria, such as those that live at hydrothermal vents on the ocean floor. There, hydrogen is formed by fast reactions between magma and water, but isotope ratio analysis showed that the hydrogen in the fracture fluids comes from a different source: slow reactions between the water and rocks, combined with radioactive decay.

Sherwood Lollar says that finding fracture fluids enriched in hydrogen by this mechanism “completely changes our conception where we might potentially find life.” Unlike hydrothermal vents, fracture fluids are common not only on Earth but Mars as well. However, she cautions that further tests need to be done. “We’ve shown that it is habitable,” says Sherwood Lollar. “That’s quite different from showing that it’s inhabited.”