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...