Earth's oldest water beneath Canada

Water that hasn't seen the light of day, or had contact with the Earth's atmosphere, for 2.5 billion years has been discovered in Ontario, Canada.

Reporting in Nature this week, a team of Canadian and UK-based scientists analysed water collected 2.7 kilometres underground from a copper and zinc mine near the city of Timmins. The water is trapped in a system of extensive volcanic deposits laid down over millions of years and dating back billions of years.

By studying the proportions in the water of a range of noble gas isotopes, which are heavier and lighter forms of the same chemical element, Manchester University geochemist Chris Ballentine and his colleagues have been able to show that the water has a chemical fingerprint consistent with having been sealed off underground, without contact with the outside world, for at least 1.5 - and possibly as long as 2.5 - billion years.

The findings are also doubly interesting because the water, which was collected carefully to avoid contamination with atmospheric air - is also crammed with dissolved methane and hydrogen.

These chemicals, which are produced when natural radioactivity in the rock splits apart water molecules, are capable of sustaining life.

This finding - of extensive, isolated and ancient subterranean water courses, raises the tantalising possibility that unique ecosystems may have evolved to exploit these sorts of environments. And although the team haven't yet reported whether there's anything living in their Canadian water, microbial communities have previously been found thriving in hydrogen-rich pockets of water cut off from the outside world for 40 million years in gold mines in South Africa.

If evidence for living organisms dating from the dawn of life on Earth does turn up, it significant raises the stakes for finding life on other planets with similar geologies and extensive sub-surface water, like Mars.