How much hydrogen awaits us underground?

In the 1990s, Barbara Sherwood Lollar descended into the Kidd Creek mine in northern Ontario, which cuts more than three kilometers into the ancient root of North America. There her team of geochemists found water that had been confined underground for more than a billion years. This ancient brine turned out to be a habitat for living microbes that feed on the hydrogen produced in reactions between the water and the rock.Decades later, Sherwood Lollar, who is a geochemist at the University of To