The enigmatic interstellar object currently journeying through our solar system has been observed behaving unlike any comet previously recorded, highlighting its extraterrestrial origins.
Researchers at Michigan State University have announced their discovery of new images of the object named 3I/ATLAS, captured months before its official identification in early July.
These images revealed that 3I/ATLAS was emitting gas or dust into space long before it began approaching our sun, a highly unusual behavior for a distant comet.
While most scientists continue to classify 3I/ATLAS as an interstellar comet rather than an alien spacecraft, the new findings suggest it originated in a completely different solar system, bestowing it with a chemical composition unlike anything we’ve encountered before.
Usually, comets in our solar system release gases such as water vapor, carbon dioxide, and trace amounts of methane and ammonia as they near the sun and heat up, prompting the release of these substances from their icy exteriors.
Contrastingly, the recent images demonstrate that 3I/ATLAS was already releasing a gas while situated at a distance six times farther than Earth’s from the sun, approximately 558 million miles away.
Scientists believe this means the mystery comet could be filled with a unique collection of molecules, including carbon monoxide, an odorless gas often produced by burning wood or fossil fuels.
Adina Feinstein, assistant professor of physics and astronomy at MSU, said: ‘3I/ATLAS gives us an opportunity to study other solar systems up close and personal, without actually needing to visit them.’
MSU researchers combed through images from NASA’s Transiting Exoplanet Survey Satellite, or TESS, and found evidence of 3I/ATLAS two months before it was officially discovered
3I/ATLAS won’t make its closest pass by Earth until December, but scientists said it’s already strange signs for a typical comet
Researchers used old images from NASA’s Transiting Exoplanet Survey Satellite (TESS) to spot 3I/ATLAS before it was officially found on July 1, 2025.
The TESS images were taken between May 7 and June 2. TESS, originally designed to find planets around other stars, takes wide pictures of the sky.
Luckily, the team realized that 3I/ATLAS’s current path lined up with the same plane the planets in our solar system travel along, making it possible for researchers to go back to look for the approaching comet.
In those reexamined pictures, the object appeared brighter than expected, suggesting it might have been releasing gases into space several months ago.
Study co-author John Noonan, a postdoctoral fellow at Auburn University, said: ‘Capturing as many observations from this prediscovery period, where 3I/ATLAS may be in telescope images but wasn’t previously identified, is essential to our understanding of how these objects ‘turn on’ as they approach our sun.’
Noonan added that 3I/ATLAS may not have been warmed up in millions, if not billions, of years, meaning it may react to our sun completely differently than other comets, which regularly visit our solar system.
The new study, published in the Astrophysical Journal Letters, also found signs that 3I/ATLAS was already showing a tail, suggesting the object was somehow activated when it was still in the outer regions of the solar system near Saturn.
Comet tails usually form when the sun’s heat causes frozen gases and dust to vaporize and escape, creating a visible trail that can stretch for millions of miles.
A new study found 3I/ATLAS was emitting gases into space long before it got close enough to our sun to melt normal gas and dust seen coming from other comets
The differences might be because 3I/ATLAS comes from a solar system which formed under very different conditions than ours.
Comets which orbit this solar system are mostly made of water ice, but 3I/ATLAS might have more carbon-based ices, which can turn into gas at colder temperatures.
This could reflect a place where the building blocks of planets and comets formed differently, possibly due to the type of star or the cosmic environment it came from.
‘Learning about other solar systems places humanity into context,’ Feinstein said.
‘One of life’s greatest questions is ‘are we alone in the universe?’ Each NASA mission gets us a little bit closer to answering this big, overarching question.’
3I/ATLAS is just days away from making its closest pass by Mars on October 3. It will be at its closest point to Earth on December 17, when the object will be approximately 223 million miles away.
