It’s no secret that interstellar object 3I/ATLAS has been getting astronomers pretty excited of late.

The comet, which originated far beyond our little corner of the universe, but has been journeying through it over the last few months, is just the third interstellar object that has been identified entering our own solar system.

Back at the beginning of October, 3I/ATLAS shot past Mars at a distance of around 18.6 million miles, and it’s trajectory will take it toward the Sun, and then out past Venus and Jupiter before it bids us farewell.

And though the comet is currently still too close to the Sun to be seen, it will be visible from Earth again in December.

But beyond its origins and uniqueness, there is something quite extraordinary about 3I/ATLAS.

Incredibly, researchers from Auburn University have detected hydroxyl (OH) gas emanating from the interstellar object as it travels on its quick-stop tour of our solar system, as they explained in a recent paper published by The Astrophysical Journal Letters.

And a trail of hydroxyl gas ultimately means water.

This is important news, since it tells us more about the evolution of comets, particularly given the unlikely visibility of the water on a comet so far away, and the amount of water it is losing (40kg per second).

This can tell us a whole lot about 3I/ATLAS’s icy structure.

Even the very fact that the comet’s water was visible to the researchers at Auburn is remarkable, as Professor Dennis Bodewits explained in a statement:

“When we detect water—or even its faint ultraviolet echo, OH—from an interstellar comet, we’re reading a note from another planetary system. It tells us that the ingredients for life’s chemistry are not unique to our own.”

And as Dr Zexi Xing continued, this was not the first time that an interstellar comet has given even our world’s best scientists a lesson on the unpredictability of objects deriving from far off in space:

“Every interstellar comet so far has been a surprise. Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS is giving up water at a distance where we didn’t expect it. Each one is rewriting what we thought we knew about how planets and comets form around stars.”

As 3I/ATLAS re-emerges later in the year, all eyes will be on the comet to see what it teaches us next.

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