The interstellar comet 3I/ATLAS has become one of the absolute protagonists of recent astronomyThis visitor from outside the Solar System is not only following a hyperbolic orbit that will lead to its permanent disappearance, but is also exhibiting a phenomenon as striking as it is unexpected: the possible presence of active ice volcanoes.
Observations obtained largely from Europe, with a central role played by Spanish teams, suggest that As the comet approached the Sun, jets of gas and dust began to activate. that emerge from within. These jets fit with what scientists describe as cryovolcanic activityThat is, eruptions caused by the sublimation of volatile ices instead of rocky lava.
An interstellar visitor with erupting ice volcanoes
The data collected shows that 3I/ATLAS began to show particularly intense activity when it approached within about 378 million kilometers of the SunAt that distance, the increase in solar radiation was sufficient to heat the outer layers of the core, causing the The ice trapped inside will turn into gas and shot out in the form of jets visible from Earth.
This behavior, known for decades in comets from the Solar System itself, in the case of 3I/ATLAS It adopted a more organized and energetic structure than usualInstead of simple diffuse sublimation, the telescopes recorded well-defined jets that seemed to originate from specific areas of the surface, which fits with the idea of active cryovolcanoes or “ice volcanoes”.
According to a study released on November 24th on the arXiv preprint serverThese icy eruptions would have occurred as the comet moved towards its perihelion, the point of closest approach to the Sun, reached the October 29Day by day, the images and measurements revealed a comet much more dynamic than expected for an interstellar object.
Instead of an inert body, fossilized after billions of years of intergalactic travel, the results suggest that 3I/ATLAS retains internal processes capable of being activated when it receives sufficient solar energy.This ability to "awaken" through ice volcanoes has forced astronomers to rethink what these visitors from other stars are really like.
The key role of European telescopes and the Joan Oró
Much of the most detailed observation of these ice volcanoes was obtained from Europe, and in particular from Spain. The Joan Oró Telescope at the Montsec Observatory, in Catalonia, played a leading role in registering the highest resolution images available of the comet during its approach to the Sun.
The teams coordinated by the researcher Josep M. Trigo-Rodríguez, from the Institute of Space Sciences (CSIC/IEEC), followed precisely how The comet's brightness suddenly increased at about 378 million kilometers from the Sun.That jump in brightness was interpreted as a clear sign that The surface began to release large amounts of gas and dust., coinciding with the activation of the cryovolcanoes.
Collaboration with other Catalan and European observatories made it possible to reconstruct a very fine temporal sequence of activityBy combining images from different centers, astronomers were able to identify the presence of directed jets emanating from specific regions of the core, reinforcing the hypothesis of an internal system of cavities and channels through which the frozen material is channeled.
In addition to ground-based telescopes, Other space instruments such as Hubble or TESS have provided information on the amount of material that the comet ejectsSome estimates suggest that, at peak activity times, 3I/ATLAS would be launching tens of kilograms of gas and dust into space per second, a rhythm that fits with episodes of intense cryovolcanism.
The European scientific community emphasizes that This type of coordinated campaign will be crucial for future interstellar visitorsThe experience with 3I/ATLAS is helping to adjust observation protocols and develop specific instruments capable of detecting subtle signals of sublimation and icy volcanism in objects that move very fast.
What's inside 3I/ATLAS: Composition and chemistry of ice volcanoes
One of the most interesting points of the study is the relationship between the composition of the comet and the eruption of these ice volcanoesSpectroscopic analyses indicate that 3I/ATLAS contains abundant solid carbon dioxide and a significant metallic fraction, with the presence of iron, nickel and sulfides mixed with ice and other volatile materials.
The proposed models suggest that, as the comet heats up, the CO2 Frozen food begins to sublimate and generate pressure in internal cavities.That pressure could allow the circulation of oxidizing fluids through the core, making contact with metallic grains rich in iron and nickelThe result would be exothermic chemical reactions capable of releasing additional energy and fueling cryovolcanic eruptions.
This mechanism would explain why, in 3I/ATLAS, The cryovolcanic activity appears more organized and powerful than in many comets in the Solar System, similar to cryovolcanism observed on CeresIt wouldn't just be ice that passively sublimates, but an internal system where the chemistry and physics of the core work together to propel the jets with more force.
To support this interpretation, the team compared the comet's spectrum with samples of carbonaceous chondrites collected by NASA in AntarcticaThese rocks, considered very primitive meteorites, preserved a mixture rich in metals and volatile compounds similar to that inferred for 3I/ATLAS. In one of the cases, the fragment studied was associated with an ancient trans-Neptunian object, which reinforces the idea of a similar composition between the comet and certain icy bodies of the outer Solar System.
Although the exact size of 3I/ATLAS is still not known in detail, observations point to a core of between a few hundred meters and several kilometers in diameterIf its width is around one kilometer and a relatively high density due to its rock and metallic contentthe mass could easily exceed the 660 billion tonsThis mass, combined with the proposed internal structure, would fit well with the comet's ability to retain heat and maintain active cryovolcanic processes.
Similarities with trans-Neptunian objects and what it reveals about other systems
Beyond the spectacle of the ice volcanoes, what has truly left researchers speechless is that The composition and behavior of 3I/ATLAS are reminiscent of icy objects orbiting beyond Neptune., such as Kuiper Belt bodies or certain dwarf planets.
Spectral analyses performed by the Trigo-Rodríguez team show patterns of interaction with light very similar to those of primitive meteorites and trans-Neptunian objectsIn other words: A comet born in a remote planetary system bears a striking resemblance to the icy worlds in our own neighborhood.The researcher himself summed it up with a phrase that has been repeated in numerous media outlets:We were all surprised".
If this similarity is confirmed by future observations, the implication is powerful: The physical and chemical processes that build icy bodies could be repeated in a very similar way in different starsThis would suggest protoplanetary disks that, despite being in separate locations in the galaxy, produce remarkably similar compositions for their comets and small bodies.
In that context, 3I/ATLAS would function as a bridge between the trans-Neptunian objects of our Solar System and the bodies that orbit around other starsFor comparative astronomy, having a messenger that brings chemical information from another system and that also behaves in a way that is understandable in light of what we already know, It opens a unique opportunity to compare theories of planetary formation.
The cosmogonic models being discussed as a result of these observations indicate that Icy worlds like 3I/ATLAS could be quite common in the galaxyIf many star systems generate comets rich in volatile ices, metals, and organic compounds, The apparent diversity of planetary systems could hide more universal underlying patterns. than we thought.
A very old traveler, fast and hard to catch
The scientific interest aroused by 3I/ATLAS is not limited to its ice volcanoes. It is only the third interstellar object detected, after 'Oumuamua and 2I/Borisov, which makes it a statistical rarityBefore 2017 we had not identified any; since then, only a handful have crossed our cosmic neighborhood within view of our telescopes.
Measurements of its trajectory indicate that The comet was traveling at more than 221.000 kilometers per hour when he was discovered. That speed, combined with his clearly hyperbolic orbit, confirms that it is not gravitationally bound to the Sun and that it comes from a distant region of the galaxy. For practical purposes, it is a one-time visitor.
Preliminary estimates suggest that Its age could even be older than that of the Solar System itself.This means that the comet has passed billions of years exposed to cosmic rays and background radiation, which have modified their outer layers. This irradiated “patina” complicates the exact reconstruction of their history, but at the same time transforms its interior into a privileged time capsule, where virtually pristine materials could have been preserved.
Astronomers insist that Each interstellar object that we manage to study contributes a crucial piece to the puzzle.They not only help us understand how other systems form and evolve, but also They allow us to assess the potential risks of these bodies if they were to cross trajectories close to Earth.Although 3I/ATLAS does not pose a danger, understanding how these objects behave, what speeds they reach, and what trajectories they follow is important. It is essential for future planetary defense analyses.
Over the past few months, his presence has generated increasing media and social media attention. There has been no shortage of outlandish theories presenting him as an alleged extraterrestrial spacecraftfueled by the rarity of the phenomenon. However, The orbital calculations and physical measurements fit perfectly with a natural comet ejected from its original system through gravitational interactions, without needing to resort to exotic explanations.
Observation window: maximum approach and countdown
In the calendar of European observatories, one of the dates marked in red is the December 19th 2025That day, if the predictions hold true, 3I/ATLAS will reach its closest point to Earth, located at about 270 million km of our planet. It won't be a spectacle visible to the naked eye for the general public, but it will a key moment to maximize the capabilities of scientific instruments.
Since the comet passed its perihelion at the end of October, Doubts about how its cryovolcanic activity will evolve have continued to growTheories range from possible fragmentation of the core to changes in the rate of gas emission. Each new image and each photometric measurement helps to refine the picture. whether the ice volcanoes will maintain their intensity or gradually fade away as the comet moves away from the Sun.
For astronomers, the margin for maneuver is short: 3I/ATLAS will follow a hyperbolic trajectory that will take it definitively out of the Solar System next yearThat means the clear nights of the coming months have become especially valuable for to obtain as much data as possible before the comet disappears from the range of our telescopes.
The teams working with the Joan Oró Telescope and other European observatories have already adjusted their programs to prioritize tracking the comet while it remains accessibleEvery gas eruption, every change in its coma, and every variation in brightness contributes to reconstruct the thermal and chemical history of this object with a level of detail that until a few years ago would have been unthinkable for an interstellar visitor.
This intensive observation campaign is complemented by numerical models that simulate the evolution of the nucleus under different scenarios of composition and internal structure. By comparing the simulations with real data, the researchers expect to better define the physical properties of the cometfrom its size to the distribution of its ice volcanoes.
As the comet continues to slowly move away from the direct influence of the Sun, The eruptions of its cryovolcanoes have become a kind of distinctive signature.These icy jets, which just a few months ago were unimaginable for an interstellar object, are now considered a direct clue that icy worlds can harbor complex internal dynamics over enormous timescales.
What has been learned in such a short time positions us 3I/ATLAS as one of the most influential comets of recent decades from a scientific point of viewIts ice volcanoes have forced a revision of previous ideas about interstellar objects, demonstrated the potential of European astronomical infrastructure—with the Joan Oró Telescope at the forefront—and raised the possibility that The chemistry of frozen worlds is repeated over and over again in very different systems to our own planetary neighborhood.
