An "oddball" interstellar visitor's colour change from red to green to gold as it draws ever-nearer to our sun could spell the end of its journey. Experts believe that comet 3I/ATLAS could be up to 14 billion years old, many times older than our Solar System, Report informs referring to Daily Star.
While many scientists confirm it is a comet, some claim there is something all the more alien going on. Avi Loeb recently noted how the object had changed from red to green and remains certain there is a link to between the object and aliens.
Interstellar comets were once thought to be very rare, but since the first verified example – 1I/Oumuamua which was spotted in 2017 – two others have been observed, explaining the ‘3' in the current cosmic visitor's name. This comes as Earth prepares for its closest brush with the "interstellar visitor" on Friday, December 19.
But, for those that manage to see it, the rare visitor will be a fascinating sight. The unusual chemical composition of 3I/ATLAS has caused it to change colour as it is heated by the Sun, initially spotted as a faint red object, it has been through a dramatic evolution as it has passed through our Solar System. And now it has changed colour again – and it could prove hugely significant.
On his YouTube channel, geophysicist Stefan Burns explains: "The evidence suggests that 3I/ATLAS was once probably a short-period comet around its host star and it was heavily thermally processed from hundreds or even thousands of orbits.
"That's why it came in with a very dark red colour with a bunch of organics after its long journey through interstellar space."
But as the Sun"s energy reached the interstellar visitor's surface, long-dormant processes began to change the massive object's appearance. "It suddenly erupted with a lot of activity," Stefan says. "it started glowing green, even a little blue at times.
"And now with that final eruptive phase having come to an end, it seems it's now going back to a dust-dominated colour, but now it's glowing gold as it moves into the constellation of Leo over the next couple of weeks."
Those violent chemical reactions have even caused the comet to accelerate, as jets of gas erupted from its surface. But while some have speculated that this "non-gravitational acceleration" might mean that 3I/ATLAS could have started life as a space probe from some alien civilisation, most reputable scientists believe it's a natural comet that simply has an unusual composition.
Stefan explains: "You had nickel emission appear very early [unusually] without the presence of iron… also a lot of cyanide and cyanogen gas emerged soon afterwards.
"This nickel production ramped up sharply, much more than expected. And so all of these are clues as to what 3I/ATLAS likely experienced in the past."
He adds that 3I/ATLAS appears to contain carbonyls – organic molecules composed of a carbon atom double-bonded to an oxygen atom, These molecules seem to be helping the nickel move into the outer surface of the object while the associated iron molecules remain buried within.
Stefan says that during the comet's journey through interstellar space it collected up a lot of "exotic materials" including the building-blocks of life: "It's very organic-rich, like a trans-neptunian object… those can create amino acids and nucleotide base pairs. Really interesting stuff."
But the most interesting aspect of 3I/ATLAS is its dramatic colour changes, which he says could be indicative of a "a new chemical change" occurring within the object. Another, less exotic recent comet, C/2025 K1 (ATLAS), displayed a similar golden hue shortly before breaking apart after a close, hot encounter with the Sun in October.
Something similar could be happening to this latest interstellar visitor, Stefan says: "And maybe is it going to break apart in the near future as it continues to head towards Jupiter."