An international team of researchers has discovered 1.2 billion-year-old groundwater deep in a gold and uranium-producing mine in Moab Khotsong, South Africa, shedding more light on how life beneath the Earth’s surface is sustained and how it can thrive on other planets.
The findings were published earlier this week in the journal nature communication†
“For the first time, we understand how energy stored deep in the Earth’s subsurface can be released over time and distributed more widely throughout the Earth’s crust,” Oliver Warr, a research associate in the Earth Sciences Department, told IPS. the University of Toronto and lead author of the study. “Think of it like a Pandora’s box with helium-and hydrogen-producing power, one that we can learn to harness for the benefit of the deep biosphere on a global scale.”
“Ten years ago we discovered billion-year-old groundwater from under the Canadian shield — this was just the beginning, it seems,” said Barbara Sherwood Lollar, a professor in the Department of Earth Sciences at the University of Toronto and corresponding author. “Now, 2.9 km below the Earth’s surface in Moab Khotsong , we have discovered that the extreme outposts of the world water cycle are more widespread than was once thought.”
Uranium and others radioactive elements occur naturally in the surrounding host rock containing mineral and ore deposits. These elements contain new information about the role of groundwater as a power generator for chemolithotrophic (or rock-eating) groups of cohabiting microorganisms previously discovered in the deep subsurface of the Earth. When elements such as uranium, thorium, and potassium decay underground, the resulting alpha, beta, and gamma rays has ripple effects and causes so-called radiogenic reactions in the surrounding rocks and liquids.
In 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 down water molecules in a process called radiolysis, producing large concentrations of hydrogen, an essential source of energy for subterranean microbial communities deep within the Earth that cannot access energy from the sun for photosynthesis.
Because of their extremely small masses, helium and neon are of unique value for identifying and quantifying transport potential. While the extremely low porosity of crystalline basement rocks in which these waters are found means that the groundwater itself is largely isolated and rarely mixes, considering their 1.2 billion-year-old age, diffusion can still occur.
“Solid materials such as plastic, stainless steel and even hard stone are eventually penetrated by diffuse helium, much like the deflation of a helium-filled balloon,” says Warr. “Our results show that diffusion transported 75 to 82 percent of the helium and neon originally produced by the radiogenic reactions through the overlying crust.”
The researchers emphasize that the study’s new insights into how much helium is diffusing from the deep Earth is a critical step forward as global helium reserves run out and the transition to more sustainable resources gains momentum.
“Humans aren’t the only life forms that depend on the energy resources of Earth’s deep subsurface,” Warr says. “Since the radiogenic reactions produce both helium and hydrogen, we can not only learn about helium reservoirs and transport, but also calculate hydrogen energy flow from the deep earth that can support underground microbes on a global scale.”
Warr notes that these calculations are vital to understanding how life is sustained below the surface on Earth, what energy might be available from radiogen-powered energy on other planets and moons in the solar system and beyond, and informing about upcoming missions to Mars, Titan, Enceladus and Europe.
Other co-authors of the paper are CJ Ballentine of the University of Oxford and researchers from Princeton University and the New Mexico Institute of Mining and Technology.
O. Warr et al, 86Kr surplus and other noble gases identify a billion-year-old radiogen-enriched groundwater system, nature communication (2022). DOI: 10.1038/s41467-022-31412-2
University of Toronto
Quote: Researchers discover the power generators of life in Earth’s oldest groundwaters (2022, July 5) retrieved July 5, 2022 from https://phys.org/news/2022-07-uncover-life-power-earth-oldest .html
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