How Old is the Water We Drink?

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Back in 2016, geologists from the University of Toronto announced they had discovered water at the bottom of an old mine in Canada that was 2 billion years old. The claim was based on the presence of dissolved salts and noble gases, which suggests how long the water had been isolated.

However, the water itself must be at least 2 billion years old but this work did not reveal when it formed. So how old is this water or indeed, any of the stuff we drink?

Today we get an answer thanks to Cecilia Ceccarelli at the Université Grenoble Alpes in France and Fujun Du at the Purple Mountain Observatory in China, who have studied the way water forms and where most of it on Earth is likely to have come from.

Their conclusion is that most of the water we drink formed during the early formation of the Solar System some 4.5 billion years ago. In other words, it is older than Earth itself.

Water Detectives

Deciphering what happened so long ago is not simple. “After all, we only have at hand the final products of the process,” say Ceccarelli and Fu.

Instead, they have studied the history of the Solar System by watching how other planetary systems are currently forming elsewhere in the galaxy.

Ceccarelli and Fu say they believe the solar system formed in four steps.

The process began with a molecular cloud probably leftover from the supernova explosion that marked the death of an earlier star. This cloud was composed mostly of hydrogen, helium, oxygen and carbon and mixed with tiny grains of carbon and silicates—all at a temperature of about 10 Kelvin.

These grains played a hugely important role in the formation of water, say the researchers. At this temperature, oxygen atoms and molecules tend to stick to […]

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