Interstellar Comet 3I/ATLAS Reveals Clues to Planetary Formation, May Be a “Primitive Carbonaceous Object”
Breaking News: New research suggests the interstellar comet 3I/ATLAS, currently making its closest approach to the Sun, is a remarkably primitive object offering a unique window into the building blocks of planetary systems beyond our own.A study posted to the preprint server arXiv reveals the comet exhibits characteristics similar to rare meteorites found in Antarctica, hinting at a composition rich in carbon and metals.
Discovered in 2023, 3I/ATLAS is only the third confirmed interstellar object to visit our solar system. Unlike previous visitors, this comet has displayed cryovolcanic activity – the eruption of volatile substances – even tho it’s relatively small, estimated to be between 0.3 kilometers (0.186 miles) and 5.6 kilometers (3.48 miles) in diameter. Researchers believe this activity is driven by the sublimation of near-surface volatile components as the comet approaches the Sun, even if full water-ice sublimation hasn’t occurred.
The team’s spectrographic analysis reveals a striking similarity between 3I/ATLAS and CR and CH chondrites, a type of carbonaceous meteorite recovered from Antarctica. Both exhibit “featureless red spectra” likely due to the presence of metal grains, sulphides, and other opaque phases.
“It means that early stages of planetary formation could produce similar types of materials, even in really remote locations of our galaxy,” the research team explains.
This suggests that the processes forming planetary systems may be universal, producing comparable materials nonetheless of location. The comet’s composition also points to the possibility of energetic Fischer-Tropsch reactions, driven by the corrosion of fine-grained metal, creating unique chemical products in the comet’s coma – a feature less common in comets originating within our solar system.
The study notes that cryovolcanism is considered a probable form of geological activity on larger Trans-Neptunian Objects (TNOs) with diameters exceeding 800 km, and the observed activity on 3I/ATLAS is consistent with expectations for a pristine TNO during a close solar approach.
Researchers emphasize the importance of future missions dedicated to directly sampling interstellar visitors. They specifically highlight ESA’s Comet Interceptor project as a crucial endeavor.
“Future intercept missions will be essential for visiting, and directly sampling these rare messengers and unlocking the record they carry from distant planetary systems,” the team concludes.”Interstellar visitors like 3I/ATLAS continue to challenge and refine our understanding of planetary-system formation and the chemical evolution of small bodies. Each newly discovered object reveals unexpected properties that test and expand current models.”
The full study is available on arXiv: https://arxiv.org/abs/2511.19112
