We’re all familiar with good old H₂O.

We drink it, we bathe in it, we hide from it when it’s falling from the skies – we’re even made up of it ourselves.

But water’s cousin, D₂O or ‘heavy water’, composed of double deuterium and oxygen (instead of double hydrogen and oxygen), is perhaps lesser known.

It is naturally found in low concentrations on our planet, but the recent discovery of D₂O in space has helped astronomers to understand more than ever before about our Solar System’s long relationship with water.

When examining the contents of a disk around the young star V883 Ori using the Atacama Large Millimeter/submillimeter Array (ALMA), scientists from the University of Milan, Italy, found something quite astounding.

Within the disk – which importantly, is the location within which planets that will one day orbit V883 Ori will form – were the first ever identified molecules of D₂O in the star’s orbit.

But that wasn’t the only reason their discovery was exciting, as Milan’s Margot Leemker explained in a statement:

“Our detection indisputably demonstrates that the water seen in this planet-forming disk must be older than the central star and formed at the earliest stages of star and planet formation. This presents a major breakthrough in understanding the journey of water through planet formation, and how this water made its way to our Solar System, and possibly Earth, through similar processes.”

This fascinating truth, that the water in the planet-forming disk likely dates back to the earliest days of the universe, has excited astronomers, with the researchers’ paper published by the journal Nature Astronomy.

The very fact that the D₂O has survived for so long, speaks to how water travels through space, and the role it can play in planetary creation – including, perhaps, our own planet.

And as the researchers go on to explain, understanding how water moves through our universe, and how ancient water can come to be a part of new worlds is fundamental to our understanding of how life on our own and other planets came to be.

Because before there is life, there must be water.

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