In 2016, researchers found the world's oldest water about 1.8 miles (3 kilometers) deep at a Canadian mine. IFL Science reported that the same team found groundwater at a similar depth in the Moab Khotsong gold and uranium mine in South Africa. Similar to the oldest water, it contains elements that allow life to survive even without access to sunlight.
In the study titled "86Kr Excess and Other Noble Gases Identify a Billion-Year-Old Radiogenically-Enriched Groundwater System," published in Nature Communications, researchers wrote that they believe their findings could provide valuable insights about microbial life on other planets.
1.2 Billion-Year-Old Groundwater in South African Mine Has the Highest Radioactive Products Ever Discovered in a Fluid
A 1.2-Billion-Year-Old Pandora Box Beneath Earth's Surface
Geologists estimated the groundwater to be at least 1.2 billion years old. They also found that it is enriched in the highest concentration of radioactive chemical element ever discovered in any fluid.
One of the researchers has described the newly discovered ancient groundwater as a "Pandora's Box of helium-and-hydrogen-producing power" that can be useful, Interesting Engineering reported.
The team investigated a process that produces helium and hydrogen far beneath the Earth's surface. Oliver Warr, a research associate at the University of Toronto's Department of Earth Sciences and the study's lead author, said that this is the first time scientists could have insights into how energy is stored deep in the Earth's subsurface and distributed broadly through the crust over time.
Barbara Sherwood Lollar, a professor at the same university and department, said that the discovery of the oldest water in Canada marked the beginning of discovering extreme ancient groundwater outposts of the world's water cycle that is more widespread than once thought.
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Ancient Groundwater Provides Insights About Other Planets
According to Sci-News, uranium and other radioactive elements naturally occur in rocks that contain minerals and ore deposits. Researchers noted that these elements hold the key to the role of the groundwater as a power generator for rock-eating or chemolithotrophic groups of co-habiting microorganisms in the deep subsurface of the planet.
When radioactive decay happens in the subsurface, it results in alpha, beta, and gamma radiation that also causes radiogenic reactions in the surrounding rocks and fluids.
At the South African gold and uranium mine, researchers found large amounts of radiogenic helium, neon, argon, and xenon, as well as an unexpected discovery of krypton 86, which was never seen before from this powerful reaction.
Moreover, the radiation breaks the water molecules in a process called radiolysis that produces large amounts of hydrogen, which is a sign of life in the deep subsurface of Earth but cannot access energy from sunlight. Since the team found the groundwater in rocks with low porosity, they believe it is largely isolated and rarely mix, causing them to be trapped for 1.2 billion years.
But still, diffusion can take place. In this case, diffusion has allowed 75% to 82% of the helium and neon to be transported to the overlying crust. Understanding this is a critical step forward as global reserves for helium is running out and the transition to more sustainable sources is gaining attention.
The study's findings are important to gain insights into how subsurface life is sustained beneath Earth and what energy might be available from radiogenic power on other planets within the Solar System and exoplanets beyond.
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