Interstellar comet 3I/ATLAS erupts icy volcanoes: discoveries about its composition.

According to ТСН: The interstellar comet 3I/ATLAS began erupting cryovolcanoes, releasing jets of ice and dust as it approached the Sun. New research has shown that this object from another star system has a composition that unexpectedly resembles the trans-Neptunian objects of our Solar System.

"Icy volcanoes" on comet 3I/ATLAS

Scientists noticed that closer to the Sun, cryovolcanoes started to appear on the comet's surface. The activation of these icy jets is associated with the comet's composition, according to a study released on the arXiv preprint server.

The results, which have yet to undergo peer review, suggest that comet 3I/ATLAS has much in common with icy trans-Neptunian objects. If confirmed, the comet, despite its origins from another star system, bears a significant resemblance to objects in our stellar neighborhood.

"We were all surprised. To be a comet formed in a distant planetary system and yet have a mixture of materials similar to trans-Neptunian objects—bodies that formed at great distances from the Sun but within our system—is incredibly astonishing," said lead author of the study, José Trigo-Rodríguez, a senior researcher at the Institute of Space Sciences (CSIC/IEEC) in Spain.

As part of the new study, Trigo-Rodríguez and his team observed the comet using the Joan Oro telescope at the Montsec Observatory in Catalonia, as well as data from other regional observatories. Astronomers closely studied the comet during its approach to perihelion—the closest point to the Sun. As the comet approaches stars, it heats up, and the ice on its surface begins to sublimate, turning into gas.

Researchers found that the comet began to sublimate more actively when it came within about 378 million km of the Sun, and started brightening sharply. The Joan Oro telescope captured detailed images of gas and dust jets, which scientists consider clear signs of cryovolcanism.

Cryovolcanoes typically occur on bodies rich in icy resources, such as trans-Neptunian objects. Trigo-Rodríguez explained that such bodies have internal heat that melts the ice and initiates cryovolcanic processes, during which steam and dust are expelled into space.

In the case of comet 3I/ATLAS, scientists believe that cryovolcanism is triggered by the destruction of the primordial material inside the comet's core. When the temperature rises above a critical level, solid carbon dioxide begins to sublimate, allowing liquid to penetrate the comet's interior and react with active metallic inclusions.

To verify the composition of the comet, scientists conducted a spectroscopic comparison with primitive chondrites—rocky meteorites collected by NASA in Antarctica. The analysis showed that comet 3I/ATLAS has much in common with these ancient remnants of the early Solar System and is likely rich in natural metals.

Carbonaceous chondrites are believed to have played an important role in the emergence of life on Earth as they brought volatile substances that contributed to the formation of the atmosphere.

The origin of comet 3I/ATLAS

The exact size of 3I/ATLAS is still unknown, but observations from the Hubble telescope suggest that its diameter could range from 440 m to 5.6 km. Calculations show that, with a width of about 1 km, its mass exceeds 600 million tons.

However, even if the comet has a composition similar to carbonaceous chondrites and exhibits traits of trans-Neptunian objects, it is not part of our system. This is confirmed by its hyperbolic trajectory. The comet was first spotted as it traveled at a speed of about 221,000 km/h, which is too fast for the Sun to capture it with its gravity.

Scientists still do not know from which star system 3I/ATLAS originates, but the path it has taken is vast. The comet has likely existed for billions of years—it may be older than the Solar System by over 3 billion years. Such a long time in interstellar space may have led to severe radiation exposure, complicating the determination of its origin.

Trigo-Rodríguez noted that studying interstellar comets is important because they may represent a potential collision threat to Earth. At the same time, he called them "extraordinary objects" deserving attention in their own right—"these are cosmic capsules that contain valuable information about the chemical processes occurring in other parts of our galaxy."

Recall that NASA previously confirmed the natural cometary origin of the object 3I/ATLAS thanks to new images obtained, among others, from the James Webb telescope. Despite unique characteristics such as a high content of carbon dioxide and atypical nickel emissions, it exhibits all the signs of a comet.