Some discoveries you file away in the part of your brain reserved for things that feel too large to fully absorb, like the fact that the light from distant stars takes so long to reach us that some of those stars have already died. The oldest water ever found on Earth belongs in that same drawer. Not in a glass at the back of a forgotten fridge. Not at the bottom of a glacier. In a mine. In Canada. Nearly two miles underground, sealed inside the rock since before complex animal life existed on this planet, sitting there for somewhere between 1.5 and 2.6 billion years while absolutely everything else happened.
When scientists discover something like this, they run tests. They send samples across the ocean and wait for results. They triangulate isotope ratios. And occasionally, apparently, they also taste it. Not a sip from a glass. A finger to the tongue, the way field geologists have always worked, chasing a data point that instruments can confirm but the human body can clock first. Saltier means older. The ancient water was very salty. It was also, for the record, terrible.
That detail is what makes this story impossible to stop thinking about. The water had been sitting in darkness, untouched, undisturbed, accumulating minerals and chemical memory for longer than the human mind is genuinely equipped to process – and the first thing a person did upon finding it was lick it. If that doesn’t tell you something about scientists, nothing will.
Down Two Miles, Into the Ancient World
In 2009, geochemist Barbara Sherwood Lollar of the University of Toronto discovered 1.6-billion-year-old water in a Canadian mine 2.4 kilometers below Earth’s surface – the oldest water ever found on the planet at the time. The mine is the Kidd Creek mine, a find that began with something as mundane as a smell. Lollar described it as “not skunky, but musty” – a sulfur-tinged scent she followed through the dark tunnels of the Kidd Creek Mine near Timmins, Ontario.
When Sherwood Lollar sent water samples to a colleague at the University of Oxford for testing, she knew this was no ordinary water. The geochemist had spent much of her career exploring some of the deepest mines in the world, finding and extracting water that was millions of years old. She waited and waited for results that should have come back promptly, then called the researcher in charge. The delay, it turned out, wasn’t an administrative problem. The researcher told her the mass spectrometer appeared broken – the readings couldn’t be right. The tests had pegged the water at 1.6 billion years old.
The fluid is highly saline – up to 10 times saltier than seawater. That’s not a quirk. It’s a record of everything that has ever leached into it from the surrounding rock across an almost incomprehensible span of time. In an interview with the Los Angeles Times, Lollar explained that the rocks formed about 2.6 billion years ago on what was an ancient ocean floor, and that some of the water may be remnants of ocean water that was in contact with the rock when it first formed, while other portions probably seeped through cracks and became trapped.
Why a Scientist Tasted It
When asked about tasting the water, Sherwood Lollar told CNN: “If you’re a geologist who works with rocks, you’ve probably licked a lot of rocks.” She noted she was looking for saltiness, since saltier water tends to be older, and the ancient liquid was “very salty and bitter” – much saltier than seawater. Describing the flavor to the Los Angeles Times, she said the first thing that jumped out was the saltiness. “Because of the reactions between the water and the rock, it is extremely salty,” she said. “It is more viscous than tap water.”
This is not as cavalier as it sounds. Tasting water to assess its chemistry is a genuine technique with deep roots in field geology – the same reason field geologists routinely lick rock samples to check texture and mineral content. The taste provided an immediate, practical data point about salinity, which in ancient groundwater is directly tied to how long the water has been isolated from the surface. Saltier means older, in the most literal sense: more time for the surrounding rock to leach minerals into the water.
The moment, while seemingly casual, provided real insight into the water’s chemical nature. The saltiness and bitterness confirmed that the water had been isolated for an extraordinarily long time, allowing for the accumulation of minerals.
How You Date a Billion-Year-Old Liquid
The obvious question is: how do you actually know how old water is? You can’t carbon-date it – that method tops out at around 50,000 years, which is practically yesterday compared to what Sherwood Lollar’s team was dealing with. The answer is noble gases.
For assessing the age of very old groundwater, scientists measure the concentration of naturally occurring radioisotopes, which decay very slowly and aren’t disturbed by chemical reactions within the water or the surrounding rocks. Noble gases such as krypton and helium have been used increasingly as age tracers to estimate the timescales of groundwater flow. By analyzing the concentration of specific isotopes such as krypton-81 or helium-4 dissolved in the groundwater, scientists can calculate precise timescales of when the water was last in contact with the surface.
Think of it like a slow-filling bathtub. Noble gases – helium, xenon, krypton – accumulate inside isolated water through the natural decay of uranium and thorium in the surrounding rock, building up in concentration with every million years that passes. The more of these gases you find, the longer the water has been sitting there. The tests involved measuring radiogenic noble gases like helium and xenon, the elements on the far right of the periodic table. “As the water sits there, it accumulates them, like passengers getting on a train,” Sherwood Lollar said.
The four-year testing process involved sending samples to the University of Oxford, running mass spectrometry across multiple gas ratios, and triangulating the results against isotopic data. By the end of it, there was no reasonable doubt: this water had been sealed in the rock since before multicellular life first appeared on Earth.
Something Was Living in It
The billion-year age would have been remarkable on its own. Then came the detail that turned a remarkable story into something genuinely astonishing. Tiny chemolithotrophic microbes – organisms that feed on chemical energy rather than sunlight – were present in the water, surviving by consuming hydrogen and sulfate. Chemolithotrophic, if that word is new: it means “rock-eating” in the most practical sense, organisms that derive energy entirely from chemical reactions with minerals rather than from photosynthesis or consuming other organisms.
According to Macleans.ca, scientists analyzed the water for traces of sulfate and hydrogen – chemicals that provide clues to the presence of microbial life from ancient times. “By looking at the sulfate in the water, we were able to see a fingerprint that’s indicative of the presence of life,” Sherwood Lollar explained.
Life, in total darkness, two miles underground, eating rocks. Not metaphorically. Literally surviving on chemical reactions with the surrounding stone, cut off from every single thing we associate with habitability, for what may have been hundreds of millions of years. If that doesn’t make you reconsider the meaning of the word “resilient,” the English language may have run out of words.
The Mine That Kept Giving
Three years after the initial discovery, scientists found what they believed to be even older water in the same area – thought to be at least 500 million years more ancient than the earlier finding. The Kidd Creek mine, it turned out, was not finished yielding surprises. Geochemical analyses at a depth of 2.4 kilometers showed the original water sample was around a billion years old. When the team went deeper – three kilometers down – in 2016, the water extracted was estimated to be even older, up to 2 billion years old.
That progression matters. The pattern suggests that the deeper you go into the ancient Canadian Shield, the further back in time you travel. The rock itself is a kind of archive, and the water trapped within its fractures is the ink.
From Ancient Water to a Cleaner Future
Sherwood Lollar didn’t stop at the discovery. A University Professor in the University of Toronto’s department of Earth sciences, she has spent nearly three decades studying deep underground water – work that has offered clues about life on other planets and, more recently, the future of energy on this one. Her find drew the attention of NASA.
The discovery led to a partnership with NASA to assess the potential for extraterrestrial life below the surface of other planets. More recently, Sherwood Lollar has been called upon to help develop safety protocols for bringing space samples back to Earth. The logic is clean: if microbial life can survive in billion-year-old water under two miles of Canadian rock, the question of whether life might exist in similar subsurface environments on Mars or other planets stops being a philosophical exercise and starts being a research question.
Her current work has taken a different turn, though no less significant. Naturally occurring hydrogen could become a valuable component in the transition toward clean energy in some locations, according to a report from the Royal Society that Sherwood Lollar led. The report examines the emerging potential of naturally occurring hydrogen, also known as “white” or “gold” hydrogen, as a low-carbon resource. Unlike most hydrogen used today – made using fossil fuels or electricity – natural hydrogen forms through chemical reactions in the Earth’s crust.
As Sherwood Lollar noted in the report: “Hydrogen is already a $135 billion industry and is a key component in critical industries such as fertiliser production.” Her argument, built on three decades of understanding how ancient water interacts with deep rock, is that the same geological processes that produced the water in Kidd Creek also generate hydrogen – and that there may be far more of it underground than anyone has yet bothered to look for. True to form, she wants the science to lead the commercial enthusiasm rather than follow it. “This is not a gold rush,” she said. “As interest grows, we need to make sure evidence stays at the centre of the conversation.”
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What This Means for How We Think About Everything
There’s something particular about this story that stays with you even after you’ve moved past the chemistry. A woman follows a smell through a dark tunnel, deep inside a mine in northern Ontario, and finds water that has been sitting undisturbed since before animals existed. She tastes it. It’s terrible. There are tiny organisms living in it. It tells us that life on Mars might be possible, and that clean energy might be sitting beneath our feet, and that the planet is doing things we’ve barely started to understand.
Sherwood Lollar grew up reading Jules Verne – her parents raised her on his classic adventure novels, and she titled one of her first undergraduate papers “Captain Nemo Was Right.” That detail is exactly right. The most significant discoveries about the Earth still happen the way they did in nineteenth-century adventure stories: by going further down than anyone has gone before, following a strange smell in the dark, and trusting that something extraordinary is waiting at the end of it.
The water had been there for two billion years. It could afford to wait for someone curious enough to find it. The fact that the first thing that happened when she did was a taste test is, in the best way, completely human.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.