Turns out the mysterious object hurtling at break-neck speeds towards Earth is even more unique than scientists first realized.
Back in July, 3I/ATLAS was identified by the NASA-funded ATLAS survey telescope in Chile.
It's only the third known object to originate from interstellar space - meaning it came from beyond our own Solar System.
The first two were Oumuamua in 2017 and Borisov in 2019.
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This new finding - the largest of the interstellar objects, thought to be around 7 miles (11.2 kilometers) wide - had scientists scratching their heads.
It's traveling too fast to be bound by the Sun's gravity, at more than 41 miles per second and the anomaly was previously described as ‘possibly hostile’ amid fears it could wreak havoc on planet Earth.
Meanwhile, Harvard physicist Avi Loeb floated the idea that the 3I/ATLAS might not be 'natural' at all, but some sort of mothership sent from an alien planet.
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He even toyed with the pros and cons of beaming a message over to the potential alien vessel, but ruled it wasn't perhaps the safest of ideas as we could be perceived as a threat.
Anyway, other organizations, including NASA, have determined that it's simply a comet, which will make its closest pass by our Sun around Halloween before continuing into deep space 'never to be seen again.' So, nothing to fear - but time will tell...
Now, the US space agency's James Webb Space Telescope has found out more about the bizarre phenomenon.
Studying the light from 3I/ATLAS, scientists have been able to determine what gases are its 'coma' - the visible, fuzzy cloud of dust surrounding the comet.
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The preprint paper of the investigation reveals that unusually, the coma is dominated by carbon dioxide, not water vapor - as is usually the case for comets from our Solar System.
In fact, the amount of carbon dioxide compared to water is about 8 to 1, which is one of the highest ratios ever seen in any comet.
It's already the largest interstellar object ever detected, and now it's even more unique.
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The unusual mix could mean a few things about ATLAS’s origin.
It might have been loaded with carbon dioxide ice since its origin, because it formed in a part of its home solar system where the chemical could easily freeze.
Another possibility is that its 'water ice' is buried too deep inside for sunlight to heat it up and release much water vapor. So, we mostly see carbon dioxide escaping instead.
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It could also mean its ices have been exposed to more radiation in space than comets in our Solar System, changing its makeup.
Either way, its an incredible opportunity for scientists to learn more about life outside our own cosmic neighbourhood. Alien mothership, or not!
Ellie Kemp