What does two-billion-year-old water taste like? Scientists discovered and tasted ancient water that holds Earth’s secrets

What does two-billion-year-old water taste like? (Image: Canva)

Back in 2016, researchers in Canada stumbled upon something unusual. Nearly three kilometres beneath the Earth’s surface, they uncovered water sealed away for more than two billion years. The discovery, made inside a mine, became the oldest known water on Earth.

Geologists led by Professor Barbara Sherwood Lollar were stunned by the find. Unlike tiny pockets of trapped liquid, this water was flowing freely. “It was bubbling right up at you, at litres per minute,” Sherwood Lollar said, describing its surprising volume.

What Did the Water Reveal About Life?
Tests showed a chemical fingerprint left behind by microbes. Researchers detected sulphate, which they believe was produced by organisms over immense timescales. “The microbes couldn’t have done this overnight,” Sherwood Lollar explained. Without sunlight, the lifeforms are thought to have survived using energy from radiation.

Assistant professor Long Li added that the sulphate was not modern. Instead, it was generated by reactions between water and surrounding rock. Such processes can last as long as the two remain in contact, possibly for billions of years.

The discovery not only offered clues about Earth’s history but also sparked speculation about life in extreme environments elsewhere. If microbes thrived in total darkness underground, could similar forms survive beneath Mars or icy moons?

But What Did It Taste Like?
One question fascinated the public more than the science itself. What does two-billion-year-old water taste like? Sherwood Lollar admitted she tested a drop on her finger. She expected saltiness, with older water often being saltier. Her verdict was clear: “very salty and bitter,” far more so than seawater.

The research, published in Nature in 2016, continues to influence studies of ancient environments and the search for extraterrestrial life. But for many, the mystery of its flavour remains the detail that lingers longest.