In a deep Canadian mine, researchers uncovered a remarkable natural archive: water trapped underground for more than 1.6 billion years. The discovery came from Kidd Creek Mine in Ontario, where geochemist Barbara Sherwood Lollar and her team studied fluid emerging from fractures nearly 2.4 kilometers below the surface.
The water is far from ordinary. It is extremely salty, about 10 times saltier than seawater, and carries chemical clues that point to long-term isolation beneath ancient rock. To determine its age, scientists analyzed noble gases such as helium, neon, argon, and xenon preserved in the fluid. The results confirmed an age far beyond earlier records for ancient water.
What makes the finding especially compelling is the biology hidden inside it. The team identified tiny microbes that appear to survive on hydrogen and sulfate in this deep subsurface environment. Their metabolism resembles energy systems seen near hydrothermal vents, environments often discussed in studies of how life may have first emerged on Earth.
According to researchers at the University of Toronto and the University of Alberta, this underground ecosystem suggests that life can persist in places once thought too isolated to support it. The discovery also strengthens scientific interest in similar hidden habitats on other worlds, including Mars, where subsurface water may still exist.
Beyond its age, the sample offers a rare glimpse into Earth's ancient geology. Kidd Creek Mine sits on the Canadian Shield, one of the planet's oldest continental regions, once part of an ancient seafloor. In that sense, the water is not only a chemical relic but also a record of deep planetary history.
And for the curious: Sherwood Lollar described the taste as intensely salty and bitter. More importantly, the find shows how much remains to be learned beneath Earth's surface, where ancient water systems may still shape the future of astrobiology and deep-Earth science.