The interstellar comet 3I/ATLAS may very well be coated in erupting “ice volcanoes,” new observations recommend.
The research’s findings, which have but to be peer-reviewed, recommend that comet 3I/ATLAS is similar to icy trans-Neptunian objects — dwarf planets and other objects that orbit the sun beyond Neptune. If this is confirmed, it means that despite coming from another solar system, comet 3I/ATLAS has a surprising amount in common with objects in our own cosmic neighborhood.
“We were all surprised,” study lead author Josep Trigo-Rodríguez, a employees main researcher on the Institute of Space Sciences (CSIC/IEEC) in Spain, informed Live Science. “Being a comet formed in a remote planetary system, it is remarkable that the mixture of materials forming the surface of the body has resemblance with trans-Neptunian objects, bodies formed at [a] large distance from the Sun but belonging to our planetary system.”
There has been countless hypothesis in regards to the origins of comet 3I/ATLAS since astronomers first noticed it in July. Much of the net hypothesis has centered round whether or not this interstellar customer may very well be an alien spacecraft. However, most astronomers are assured that 3I/ATLAS is a comet from an unknown star system.
Comet 3I/ATLAS is barely the third interstellar object ever recorded, and affords researchers a uncommon alternative to study extra about situations round different stars and within the deep previous (comet 3I/ATLAS may very well be billions of years older than our system). This signifies that scientists are scrambling to check the thing earlier than it departs our photo voltaic system without end subsequent 12 months.
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 fastidiously because it approached its closest level to our star, often known as perihelion, on Oct. 29. Comets warmth up as they fly nearer to stars, inflicting ice on their floor to sublimate into fuel, which researchers can then detect and research.
The researchers discovered that the comet entered a extra intense sublimation stage when it received inside about 235,000,000 miles (378 million kilometers) of the solar, whereas additionally brightening quickly. Using the Joan Oró Telescope, they snapped the highest-resolution pictures but of jets of fuel and dirt particles coming off the comet, which they interpreted as clear indicators of cryovolcanism.
Cryovolcanoes are usually present in planetary our bodies which might be wealthy in ice, like trans-Neptunian objects. Trigo-Rodríguez famous that these planetary our bodies have inner warmth that melts the ice and produces the cryovolcanoes, which launch vapor and dirt into area.
PRE-PERIHELION STUDY OF #COMET #3IATLAS with our findings about its spectroscopic similitude with CR carbonaceous chondrites. Manuscript submitted for publication wherein 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
In the case of comet 3I/ATLAS, the researchers imagine that the cryovolcanism is pushed by the corrosion of pristine materials locked contained in the comet. As the solar heated the comet, the brink at which strong carbon dioxide (dry ice) sublimated into fuel 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 in regards to the comet’s composition, the researchers ran a spectroscopic comparability (analyzing how matter interacts with mild) utilizing primitive and pristine rocky meteorites referred to as carbonaceous chondrites that NASA collected from Antarctica.
One of those Antarctic samples contained what the researchers imagine is a chunk of a trans-Neptunian object. The evaluation revealed that comet 3I/ATLAS was much like these remnants from the earliest days of our solar system, and is probably going wealthy in pure metallic.
Carbonaceous chondrites are believed to have performed a job in life’s origins on Earth, bringing risky supplies that helped set up our ambiance and different situations obligatory for all times, based on the Natural History Museum in London.
Comet 3I/ATLAS origins
While 3I/ATLAS’s exact size is still uncertain, Hubble Space Telescope observations recommend that it is someplace between 1,400 toes (440 meters) and three.5 miles (5.6 kilometers) vast. Rodriguez and his colleagues calculated that if the comet is 0.6 miles (1 km) vast and has the rocky composition they believe it has, then its mass could be greater than 660 million tons (600 million metric tons).
However, even when 3I/ATLAS has an identical composition to carbonaceous chondrites and behaves like trans-Neptunian objects approaching the solar, it is nonetheless surely not from our photo voltaic system. That’s 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, based on NASA.
Researchers do not know which star system comet 3I/ATLAS originated from, nevertheless it 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. In truth, 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 troublesome.
Trigo-Rodríguez famous that it is vital to check and observe interstellar comets as a result of they’re a possible collision hazard for Earth. However, he additionally described them as “extraordinary objects” in their very own proper and worthy of consideration.
They “are space capsules, containing valuable information about the chemistry ongoing in another location of our galaxy,” Trigo-Rodríguez mentioned.