An international team led by the University of Toronto researchers have discovered 1.2-billion-year-old groundwater in South Africa, shedding more light on how life is sustained below the Earth’s surface and how it may thrive on other planets.
The same team previously discovered one-billion-year-old groundwaters in a mine, in Ontario, Canada, but the newly discovered waters in a gold- and uranium-producing mine in Moab Khotsong, South Africa, are the oldest so far.
Uranium and other radioactive elements naturally occur in the surrounding host rock that contains mineral and ore deposits. These elements hold new information about the groundwater’s role as a power generator for microorganisms living in the Earth’s deep subsurface.
When elements like uranium, thorium and potassium decay in the subsurface, the resulting alpha, beta, and gamma radiation has ripple effects, triggering what are called radiogenic reactions in the surrounding rocks and fluids, explained the researchers in their study published in the latest issue of the journal Nature Communication.
At Moab Khotsong, the researchers found large amounts of radiogenic helium, neon, argon and xenon, and an unprecedented discovery of an isotope of krypton – a never-before-seen tracer of this powerful reaction history.
“The radiation also breaks apart water molecules in a process called radiolysis, producing large concentrations of hydrogen, an essential energy source for subsurface microbial communities deep in the Earth that are unable to access energy from the sun for photosynthesis,” explains Oliver Warr, research associate in the Department of Earth Sciences at the University of Toronto and lead author of the study.
“Humans are not the only life-forms relying on the energy resources of the Earth’s deep subsurface. Since the radiogenic reactions produce both helium and hydrogen can sustain subsurface microbes on a global scale,” says Warr.
Although these calculations are vital for understanding how subsurface life is sustained on Earth, they might also help study other planets and moons in the solar system and beyond, informing upcoming missions to Mars, Titan, Enceladus and Europa, he notes.
