3I/ATLAS Data Reignites Ice-Volcano Feud And Experts Can't Agree What It Means

A mysterious celestial visitor is forcing scientists to rethink everything they thought they knew about comets.

The interstellar object 3I/ATLAS has delivered a wave of contradictory data since its discovery. Some suggest it is a primitive, volatile-rich comet, while others argue it behaves in ways that defy standard cometary physics. The result is a bitter divide among astronomers whose interpretations could reshape our understanding of how bodies from other star systems behave when they enter our Solar System.

As 3I/ATLAS speeds through our cosmic neighbourhood, studies showing carbon–dioxide–rich outgassing, metal-laden composition, and possible cryovolcanic jets challenge conventional cometary models and raise serious questions about the origins and chemistry of interstellar objects.

An Interstellar Visitor With Cometary Traits

3I/ATLAS was first detected on 1 July 2025 by the ATLAS survey telescope in Chile. Its hyperbolic trajectory, unmatched speed, and unbound orbit confirmed it as the third known interstellar object ever observed.

Follow-up observations revealed that 3I/ATLAS carried a fuzzy envelope of gas and dust, a 'coma' typical of comets, and showed rapid brightening as it approached the Sun. Measurements from the space-based observatory James Webb Space Telescope (JWST) in August 2025 detected a coma dominated by carbon dioxide (CO₂), alongside smaller amounts of water (H₂O), carbon monoxide (CO), and other volatile molecules.

These findings, especially the strong CO₂/H₂O mixing ratio, stand out among comets observed within our Solar System, marking 3I/ATLAS as chemically distinct.

Meanwhile, ultraviolet observations from the space-based Swift Observatory revealed hydroxyl emissions, a clear signature of water loss, at a distance from the Sun where water sublimation is typically ineffective. These emissions suggest ongoing water-driven activity even far from perihelion, a trait seldom seen in 'standard' comets.

Taken at face value, 3I/ATLAS appears to be a pristine, volatile-rich interstellar comet, perhaps even analogous to cosmic bodies that formed in the outer reaches of other star systems.

Cryovolcanism And Metal-Rich Composition: A New Comet Paradigm?

A study released on 24 November 2025 on the pre-print server arXiv titled 'Spectrophotometric evidence for a metal-bearing, carbonaceous, and pristine interstellar comet 3I/ATLAS' argues that 3I/ATLAS may not follow the standard comet template.

The authors compared spectroscopic data from 3I/ATLAS with pristine carbonaceous chondrites collected from Antarctica, meteorites believed to preserve some of the oldest, unaltered material in our Solar System. The spectral similarity led researchers to conclude that 3I/ATLAS is metal-rich, carbonaceous, and likely undergoing cryovolcanic activity, akin to what occurs in icy bodies from the outer Solar System, such as trans-Neptunian Objects (TNOs).

In this model, the interplay between abundant water ice and native metals (e.g., nickel and iron) triggers catalytic chemical reactions, so-called Fischer–Tropsch processes, as the comet warms. These reactions would release energy and volatile compounds, driving jets of gas and dust upward like 'ice volcanoes.'

Unlike traditional comets, which generally shed volatiles through solar heating of surface ices, cryovolcanism originates deep within and depends on internal chemistry and structure. If confirmed, this mechanism broadens the diversity of known cometary behaviours and suggests interstellar comets may harbour far more complex chemistries than previously imagined.

Controversy And Doubt: The Dividing Lines Among Experts

Not all researchers are convinced. Some emphasise that despite the unusual chemistry, 3I/ATLAS still fits within an expanded cometary model. Others, most notably astrophysicist Avi Loeb, argue the anomalies are sufficiently extreme to question whether 3I/ATLAS is even a comet.

Loeb has drawn attention to the object's periodic light fluctuations every 16.16 hours, a regular rhythm of brightness changes too structured for a mere spinning icy rock. He suggests these pulses might stem from periodic bursts of gas and dust, a 'heartbeat'-like signature, rather than rotational modulation.

Critics of the cosmic-rock model also point to the unusually strong metal signatures and the composition of the coma, especially the high relative abundance of CO₂ compared with water, as inconsistent with most comets. The discrepancy between the required volatile mass to sustain observed jets and the measured size of the nucleus challenges standard comet physics.

On the other hand, proponents of a cometary origin maintain that while 3I/ATLAS expands the range of what comets can be, it does not necessarily break comet theory. The latest spectrophotometric study argues for a 'pristine, volatile-rich interstellar comet' undergoing cryovolcanism, not an alien spacecraft or exotic phenomenon.

Thus, the debate remains unresolved: 3I/ATLAS challenges conventional definitions but does not yet force a consensus shift.

Broader Implications For Interstellar Science

If 3I/ATLAS is indeed cryovolcanic and metal-rich, it suggests that small bodies formed in other star systems can retain volatile and metallic inventories over billions of years. That would have major implications for our understanding of planetesimal formation and chemistry across the galaxy.

Moreover, it raises the possibility that interstellar objects arriving in the Solar System might bring previously unobserved combinations of ices, metals, and organics, and that cryovolcanism may be a common exo-cometary process, not a unique oddity.

Finally, the controversy itself underscores a broader truth: interstellar visitors like 3I/ATLAS may strain our existing taxonomies. The only way forward, many scientists argue, is more data, including continued spectral monitoring, high-resolution imaging, and ideally a sample-return mission in a future encounter.

3I/ATLAS remains a cosmic enigma, at once a comet, perhaps, but one whose behaviour forces astronomers to question what comets really are.