Much like on Earth's surface, water and rock reside deep within its crust, and they date to the earliest parts of the planet's history—leaving researchers fascinated by the secrets they may hold. In a new study published in Nature, they explain that not only is there more water miles below Earth's surface than in all its rivers, swamps, and lakes put together, but it may actually contain life. After compiling data from 19 mine sites in Canada, South Africa, and Scandinavia, researchers discovered the 2.5 cubic miles of water was reacting with ancient rocks to release hydrogen gas, reports the BBC, a possible food source. In fact, the evidence they gathered "doubles the estimate of hydrogen produced on Earth."
In some areas, they found hydrogen production "equal to that produced in the oceanic crust," a researcher says, suggesting complex microbial communities could be sheltered deep below, just as they are around hydrothermal vents on the ocean floor. "Until our most recent work, the hydrogen production in the continental crust was calculated to be negligible: close to zero," he adds. The research team next hopes to search for evidence of life and discover "the differences in the kinds of life we might find in one fracture versus another." The study may give hope to those searching for life on Mars, which also hosts billions-of-years-old rocks that may produce hydrogen, adds Science Daily. (Just found on the Red Planet: methane.)