"Old" might not top the list of the adjectives you'd use to describe water, but that could very well change after reading this story: Scientists say they've found water whose age clocks in at no less than 1.5 billion years, making it the oldest cache to have ever been discovered. (As the BBC explains, the only water to top it is "minute quantities" contained in some rock minerals.) Gold miners in Timmins, Ontario, were the ones who uncovered the water while drilling into bedrock; NPR reports that the team behind the discovery had been requesting such samples from a number of mines; a trio of dating techniques revealed this particular water to be remarkable—between 1.5 billion and 2.6 billion years old.
The BBC reports the water likely didn't begin its ancient life 1.5 miles beneath the surface: It would have seeped from above ground through the earth, eventually becoming trapped. As a geochemist involved in the study explains, "The fluids that we see now are actually preservations of ancient oceans." But that may not be the most interesting part: The water, which contains a good deal of hydrogen, could hold ancient life, too, and the scientists are currently testing samples to see if that's the case. And if it is, that could fuel hope that the same kind of life persists on Mars, which was once covered in oceans as well.