The interstellar comet 3I/ATLAS may very well be coated in erupting “ice volcanoes,” new observations counsel.
The research’s findings, which have but to be peer-reviewed, counsel that comet 3I/ATLAS is just like icy trans-Neptunian objects — dwarf planets and different objects that orbit the solar past Neptune. If that is confirmed, it signifies that regardless of coming from one other photo voltaic system, comet 3I/ATLAS has a shocking quantity in frequent with objects in our personal cosmic neighborhood.
“We had been all stunned,” research lead creator Josep Trigo-Rodríguez, a employees main researcher on the Institute of Area Sciences (CSIC/IEEC) in Spain, instructed Stay Science. “Being a comet shaped in a distant planetary system, it’s exceptional that the combination of supplies forming the floor of the physique has resemblance with trans-Neptunian objects, our bodies shaped at [a] giant distance from the Solar however belonging to our planetary system.”
There was limitless hypothesis concerning the origins of comet 3I/ATLAS since astronomers first noticed it in July. A lot of the net hypothesis has centered round whether or not this interstellar customer may very well be an alien spacecraft. Nevertheless, most astronomers are assured that 3I/ATLAS is a comet from an unknown star system.
Comet 3I/ATLAS is simply the third interstellar object ever recorded, and gives researchers a uncommon alternative to be taught extra about circumstances round different stars and within the deep previous (comet 3I/ATLAS may very well be billions of years older than our system). Which means scientists are scrambling to review the article earlier than it departs our photo voltaic system eternally subsequent yr.
For the brand new research, Trigo-Rodríguez and his colleagues studied the comet utilizing the Joan Oró Telescope on the Montsec Observatory within the northeastern Catalonia area of Spain, pairing its observations with these made by different observatories within the area. The astronomers watched the comet rigorously because it approached its closest level to our star, referred to as perihelion, on Oct. 29. Comets warmth up as they fly nearer to stars, inflicting ice on their floor to sublimate into gasoline, which researchers can then detect and research.
The researchers discovered that the comet entered a extra intense sublimation stage when it obtained inside about 235,000,000 miles (378 million kilometers) of the solar, whereas additionally brightening quickly. Utilizing the Joan Oró Telescope, they snapped the highest-resolution photos but of jets of gasoline and mud particles coming off the comet, which they interpreted as clear indicators of cryovolcanism.
Cryovolcanoes are sometimes present in planetary our bodies which are wealthy in ice, like trans-Neptunian objects. Trigo-Rodríguez famous that these planetary our bodies have inside warmth that melts the ice and produces the cryovolcanoes, which launch vapor and mud into area.
PRE-PERIHELION STUDY OF #COMET #3IATLAS with our findings about its spectroscopic similitude with CR carbonaceous chondrites. Manuscript submitted for publication during which we suggest it’s a #TNO-like physique experiencing #cryovolcanism
Now in Cornell Univ. @arxiv repository:
➡️ arxiv.org/abs/2511.19112— @joseptrigo.bsky.social (@joseptrigo.bsky.social.bsky.social) 2025-12-01T19:02:15.194Z
Within the case of comet 3I/ATLAS, the researchers consider that the cryovolcanism is pushed by the corrosion of pristine materials locked contained in the comet. Because the solar heated the comet, the brink at which stable carbon dioxide (dry ice) sublimated into gasoline was breached. This then enabled an oxidizing liquid to movement into the comet’s inside and react with reactive metallic grains like nickel and iron sulfides.
To check their theories concerning the comet’s composition, the researchers ran a spectroscopic comparability (analyzing how matter interacts with mild) utilizing primitive and pristine rocky meteorites known as carbonaceous chondrites that NASA collected from Antarctica.
One in all these Antarctic samples contained what the researchers consider is a bit of a trans-Neptunian object. The evaluation revealed that comet 3I/ATLAS was just like these remnants from the earliest days of our photo voltaic system, and is probably going wealthy in pure steel.
Carbonaceous chondrites are believed to have performed a task in life’s origins on Earth, bringing unstable supplies that helped set up our ambiance and different circumstances mandatory for all times, in accordance with the Pure Historical past Museum in London.
Comet 3I/ATLAS origins
Whereas 3I/ATLAS’s actual measurement remains to be unsure, Hubble Area Telescope observations counsel that it is someplace between 1,400 toes (440 meters) and three.5 miles (5.6 kilometers) huge. Rodriguez and his colleagues calculated that if the comet is 0.6 miles (1 km) huge and has the rocky composition they believe it has, then its mass can be greater than 660 million tons (600 million metric tons).
Nevertheless, even when 3I/ATLAS has the same composition to carbonaceous chondrites and behaves like trans-Neptunian objects approaching the solar, it is nonetheless definitely not from our photo voltaic system. That is due to its hyperbolic trajectory, alongside which scientists first seen it zooming at round 137,000 miles per hour (221,000 kilometers per hour) — too quick to be certain to our solar’s gravity, in accordance with NASA.
Researchers do not know which star system comet 3I/ATLAS originated from, but it surely has actually travelled a great distance. The comet is probably going billions of years outdated and probably greater than 3 billion years older than our personal photo voltaic system. The truth is, the comet has spent a lot time in area that it may very well be extraordinarily irradiated, which might make deciphering its origins much more tough.
Trigo-Rodríguez famous that it is vital to review and monitor interstellar comets as a result of they’re a possible collision hazard for Earth. Nevertheless, he additionally described them as “extraordinary objects” in their very own proper and worthy of consideration.
They “are area capsules, containing precious details about the chemistry ongoing in one other location of our galaxy,” Trigo-Rodríguez stated.
