Spanish scientists have recorded evidence of cryovolcanic eruptions on the interstellar comet 3I/ATLAS, the third such object detected in our Sistema Solar. The observations took place at Observatório Montsec, at Catalunha, using Telescópio Joan Oró, as the comet approached Sol in October 2025. The Esse phenomenon suggests a composition rich in ice and primitive materials, similar to objects beyond
The comet, discovered in July 2025 by the ATLAS system in Chile, travels at 221 thousand km/h in a hyperbolic orbit, confirming its origin in another star system. Pesquisadores interpret the jets of gas and dust as a result of the sublimation of carbon dioxide, which releases oxidizing liquids inside the celestial body. Essas eruptions intensified about 378 million kilometers from Sol, revealing spiral structures on the surface.
- The composition includes iron, nickel and reactive sulfides, comparable to primitive carbonaceous chondrites.
- The estimated diameter varies between 440 meters and 5.6 kilometers, with a mass of more than 600 million metric tons.
- Possible age of 7 to 14 billion years, before the formation of our Sistema Solar.
This discovery offers clues about chemical conditions in distant star systems, without posing a risk of collision with Terra.
Initial observations at perihelion
Astronomers have been monitoring the comet since July, but activity increased dramatically in October. Perihelion occurred on October 29, 2025, at 1.36 astronomical units from Sol.
Images from Telescópio Joan Oró captured high-resolution jets, previously unheard of. Esses data was complemented by regional observatories on Espanha.
Sublimation of dry ice generated vapor and dust, visible at specific wavelengths.
Composition and similarities with Sistema Solar
Comet 3I/ATLAS shares traits with trans-Neptunian objects, such as ice-rich dwarf planets. Análises spectroscopy compared it to carbonaceous chondritic meteorites collected at Antártida.
These primitive materials contain natural, volatile metals, similar to those that helped form Earth’s atmosphere.
Researchers noticed internal chemical reactions, driven by solar heating, that release gases such as carbon monoxide and cyanide.
The presence of atomic nickel vapor reinforces the hypothesis of a preserved metallic nucleus.
PRE-PERIHELION STUDY OF #COMET #3IATLAS with our findings about its spectroscopic similarity with CR carbonaceous chondrites. Manuscript submitted for publication in which we propose it is a #TNO-like body experiencing #cryovolcanism Now in Cornell Univ. @arxiv repository: ➡️ arxiv.org/abs/2511.19112
—Prof. Josep M. Trigo-Rodríguez (@joseptrigo.bsky.social) November 25, 2025 at 11:28
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Mechanism of cryovolcanic eruptions
Cryovolcanoes emerge on icy bodies when internal heat melts ice, expelling steam and dust. In the case of 3I/ATLAS, the process differs because it depends on the corrosion of pristine materials.
Solar heating exceeded the sublimation threshold for solid CO2, allowing the flow of oxidizing liquids. Esses react with metallic grains, generating the observed spiral jets.
Unlike volcanoes at Plutão or Encélado, here the mechanism is externally driven, with no evidence of significant radioactive heat.
Studies indicate that this activity explains the sudden brightness of the comet 378 million kilometers from Sol.
Interstellar trajectory and origins
The comet entered our Sistema Solar from the direction of Sagitário, close to the galactic center. Sua excessive speed confirms that it is not linked to solar gravity.
Orbital dynamics suggest origin in the thick disk of Via Láctea, estimated to be billions of years old.
Telescópio Espacial Hubble measured its size at between 440 meters and 5.6 kilometers. The mass, for a body 1 km in diameter, exceeds 600 million tons.
Observations from multiple missions
Nasa coordinated campaigns with probes such as Perseverance in Marte and MAVEN, capturing images of the gas coma.
Mars Reconnaissance Orbiter refined the trajectory in October, reducing uncertainty by a factor of ten.
James Webb Space Telescope detected abundant carbon dioxide, with traces of water ice and carbonyl sulfide.
This data reveals a halo of gas and dust, with cyanide emissions similar to solar comets.
Scientific importance of the visitor
Interstellar objects like 3I/ATLAS act as time capsules, preserving chemistry from other stellar systems.
Their analysis helps understand distant planetary formation, including roles in origins of life via volatile delivery.
With departure scheduled for 2026, observations continue until total removal.
Radio detection at 1420 MHz, although natural, ruled out extraterrestrial speculation.
The comet will make its closest approach to Terra on December 19, 2025, at 270 million kilometers, visible with amateur telescopes.
Imaging and spectroscopic data
Photometry tracked the increasing pre-perihelion brightness, with peaks at infrared wavelengths.
Comparisons with Antarctic samples confirmed similarities with carbon-rich CR chondrites.
These meteorites represent remnants of the early solar nebula.
Future of interstellar research
Discoveries in 3I/ATLAS boost proposals for future interceptor missions.
Its rare metallic composition suggests accretion processes in alien protoplanetary disks.
Astronomers emphasize the value in monitoring these visitors to mitigate potential, albeit rare, risks.
