3I/ATLAS Mystery Deepens: Rare Metal Core Is Fueling Violent Ice Volcanoes

A ghost from a distant stellar nursery, a cosmic interloper untouched by the four-and-a-half-billion-year history of our own planetary neighbourhood, has arrived. Interstellar comet 3I/ATLAS represents an extraordinary opportunity for planetary scientists and astronomers worldwide.

This object is only the second confirmed cometary body known to have traversed the vast gulf between stars and entered the Solar System, following the ground-breaking discovery of 'Oumuamua. 3I/ATLAS was first detected on July 1, 2025 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope in Río Hurtado, Chile.

Its mere presence challenges our understanding of cosmic migration and the chemical evolution of star systems, making every observation critical. The cosmogonic considerations surrounding its formation suggest a truly robust and ancient object, potentially possessing an unusually high tensile strength and a substantial metal fraction within its core.

This unique blend of characteristics is precisely why its close approach to the sun has captivated the scientific community, prompting intensive photometric and spectroscopic studies. The comet followed an extremely hyperbolic trajectory, confirming its interstellar origin. It reached perihelion (closest approach to the sun) on October 29, 2025, at a distance of 1.36 AU (about 203 million km), positioning it between the orbits of Earth and Mars, before beginning its high-speed exit from the Solar System.

Unlocking the Pristine Secrets of Interstellar Comet 3I/ATLAS

To decipher the origin and composition of this rare visitor, researchers undertook a meticulous comparison of observations from 3I/ATLAS with terrestrial samples. Specifically, they present photometric observations tracing the comet's journey along its inbound trajectory towards perihelion. Crucially, they performed a spectroscopic comparison of the object's reflected light to pristine carbonaceous chondrites retrieved from the NASA Antarctic collection.

These meteorites are considered some of the most untouched and chemically primitive materials available to science, often dating back to the Solar System's earliest days. The remarkable spectral similarities uncovered by this research lead to a compelling conclusion: the evidence indicates that 3I/ATLAS may be a primitive carbonaceous object.

However, its primitiveness is mixed with signs of complex, solar-driven activity. The data suggests that the comet is likely enriched in native metal and is undergoing significant aqueous alteration — chemical changes driven by the presence of water — as it rapidly approaches the warmth of the sun. Furthermore, the observations indicate it is experiencing cryovolcanism, a process of icy, rather than molten, eruptions.

This cryovolcanism is theorised to be the mechanism behind the observed jet structures and the comet's rapid brightening as it nears the sun, acting as the 'violent ice volcanoes' suggested by the headline. This behaviour is precisely what one might expect for a pristine, chemically volatile body originating from the frigid expanses beyond Neptune, such as a Trans-Neptunian Object or an Oort Cloud body, yet it is an exotic traveller from another star system.

The Role of Metal and Water in the Unusual Activity of 3I/ATLAS

The proposed composition — a potent combination of elevated metal abundance and a substantial reservoir of abundant water ice — is the key to accounting for the unusual coma morphology and chemical products reported to date. Comets generally form a diffuse envelope of gas and dust called a 'coma' as they near the sun, but 3I/ATLAS is behaving distinctively.

Observations have reported a high concentration of nickel and iron in the gas plume, which provides direct evidence of the metal-bearing composition of the nucleus. The science posits a unique chemical pathway driving this activity: the corrosion of fine-grained metal grains.

This metal corrosion, when interacting with the comet's abundant water ice, is theorised to originate energetic Fischer-Tropsch reactions. These are catalytic processes that convert a mixture of carbon monoxide and hydrogen into various complex hydrocarbons, essentially generating specific chemical products within the coma that are distinctly uncommon in other comets. The products of these reactions in the coma are predicted to include complex organic molecules, specifically long-chain hydrocarbons, which would be highly unusual for a standard solar system comet and would serve as the 'fuel' driving the activity mentioned in the headline.

The reason for this rarity lies in the fact that most Solar System comets formed in the outer solar system and, crucially, did not inherit so much metal from their parent stellar cloud. This lack of initial metal abundance means the necessary catalyst for these energetic reactions is absent in most of our home-grown comets. 3I/ATLAS provides a compelling case study on the dramatic difference a metal-rich starting material can make in the chemical output of a cometary body.

A Window to Distant Worlds

Interstellar objects like 3I/ATLAS offer scientists rare, invaluable opportunities to investigate physical and chemical processes in distant minor bodies. By studying this alien visitor, we can gain new perspectives on analogous bodies within our own Solar System, including the mysterious trans-Neptunian objects and the myriad of icy bodies within the Oort Cloud comets.

Its composition and dynamic activity serve as a comparative baseline, helping us realise that the building blocks for planetary systems elsewhere might be fundamentally different from, or surprisingly similar to, our own. The ongoing study of this rare celestial wanderer will undoubtedly revolutionise our understanding of planet formation across the galaxy.

The interstellar comet 3I/ATLAS may have already swung around the sun and begun its long journey back into the depths of space, but the data it left behind is just starting to reveal its secrets. As astronomers continue to analyse the unique metal-driven chemistry and the cryovolcanism powering its spectacular activity, we stand at the threshold of a new understanding of planet formation far beyond our own star.

Originally published on IBTimes UK