An astronomical enigma, the interstellar comet 3I/ATLAS, has begun to reveal some of its deepest secrets. New research suggests this rare visitor from another star system may be covered in erupting “ice volcanoes,” a dramatic finding that offers a glimpse into the dynamic forces shaping objects far beyond our sun. These cryovolcanoes, as scientists call them, were observed to activate as 3I/ATLAS approached the sun, ejecting icy jets from its surface.
The comet, only the third interstellar object ever recorded, has been a source of intense speculation since its discovery last July. Most astronomers believe it originated from an unknown star system, making it an invaluable, if fleeting, opportunity for researchers to study the conditions that prevailed around other stars, possibly billions of years before our own solar system formed. Scientists are working against the clock to gather as much information as possible before 3I/ATLAS leaves our cosmic neighborhood for good.
What makes the recent findings particularly striking is the comet’s surprising resemblance to objects much closer to home. The study, though still awaiting peer review, proposes that 3I/ATLAS shares characteristics with icy trans-Neptunian objects, such as dwarf planets and other bodies that orbit our sun beyond Neptune. This unexpected similarity between an interstellar traveler and residents of our own outer solar system has left the scientific community astonished.
Josep M. Trigo-Rodríguez, a Spanish physicist, planetary scientist, and professor involved in the study, articulated the sentiment: “We are all surprised.” He noted the remarkable fact that the blend of materials forming the comet’s surface appears to be akin to trans-Neptunian objects, which are also formed at great distances from our sun but are definitively part of our solar system. This suggests a potential commonality in the building blocks of planetary systems, even those far apart.
For this research, Trigo-Rodríguez and his colleagues, Maria Gritsevich and Jürgen Blum, employed the Joan Oró telescope at the Montseny Observatory in Catalonia, combining their observations with data from other observatories. They meticulously watched 3I/ATLAS as it neared its perihelion—its closest point to the sun—on October 29. As comets warm during their approach to stars, the ice on their surfaces sublimates into gas, a process that allows researchers to detect and analyze their composition.
The data gathered points to 3I/ATLAS being a “primitive carbonaceous object,” likely rich in native metal. The study suggests it underwent significant aqueous alteration and cryovolcanism as it neared the sun, a behavior consistent with a trans-Neptunian object. This combination of high metal and ice abundance is proposed to explain the comet’s unusual coma morphology and the specific chemicals detected so far. The corrosion of fine-grain metal, for instance, could trigger energetic Fischer-Tropsch reactions, producing unique chemicals in the coma that are less common in comets formed in our outer solar system, which typically contain less metal. The preliminary findings of this study have been made available in arXiv, a preprint repository managed by Cornell University.