On a planet with an unchanging amount of water, and a pretty good idea where all of it is, scientists have uncovered something startling up in Ontario, Canada. Water locked deep under Canadian bedrock was slowly seeping out of tunnels that gold miners were drilling in the hills. When a few British scientists caught word, they asked to sample the water. They discovered it was more than one billion years old.
How do you test water’s age? Not easily, it turns out. Generally you need a large amount of water, and a laboratory to do complex chemical analysis. There are a few ways to date water, but the most common is by testing isotopes of hydrogen and helium. Both are found in large supply in the universe, and fortunately for chemists, both also decay at certain known intervals. Measuring those intervals essentially gives you a rough estimate of how long the water has been stagnant, without the introduction of new hydrogen or helium.
In this case, the isotopes were quite old. The scientists put the number at 1.5 billion years, but it could be older—by a magnitude of another billion, said geochemist Greg Holland. It was likely a remnant of ancient oceans before it was covered by today’s landmasses. Yet it’s not the water that really interests sceintists. Locked with that ancient water may be single-celled microbes that have pretty much been living on a different planet for nearly half of Earth’s existence. That’s longer than humans have lived on Earth. They’d pre-date the dinosaurs by more than 750 million years.
Why does it matter? That’s a question we often ask in science, sometimes with less-than-satisfying answers. This time, however, the purpose might be nothing short of helping explain the arc of evolution. These microbes may turn out to be some of the first aliens humans have discovered, and on our own planet to boot. They’ve evolved on different timeline in their own closed ecosystem, giving us a parallel track of Earth’s natural history. Understanding them could offer an alternate track to study evolution—and get us closer to knowing just how much life there could be locked underground on other planets.