Ancient Interstellar Visitor 3I/ATLAS Carries CO2-Rich Coma Through Our Solar System
3I/ATLAS is the third confirmed interstellar visitor to our solar system, on a hyperbolic trajectory that brought it to about 1.4 AU from the Sun in Oct 2025 and a close Earth approach in Dec 2025; Webb’s near-infrared spectra reveal a carbon dioxide–rich coma—with CO2 outweighing water by about eight to one—along with other volatiles, suggesting a nucleus intrinsically rich in CO2 and an origin well before the Sun. Isotopic and motion analyses hint at a formation roughly 10–12 billion years ago, making it possibly older than the Sun; SETI searches found no technosignatures, and the object is now outbound and fading. The event foreshadows more interstellar visitors detectable by future surveys like the Vera C. Rubin Observatory.
- 3I/ATLAS is only the third confirmed interstellar object ever detected passing through our solar system. It may be older than the Sun itself, and Webb observations show it is carrying an unusually carbon dioxide-rich coma as it swings past once before leaving fo Space Daily
- SETI Institute Looks for Signs of Technology in Interstellar Visitor 3I/ATLAS SETI
- NASA’s Webb Detects Methane on Interstellar Comet 3I/ATLAS NASA Science (.gov)
- Radio scans find no alien tech from the latest interstellar comet AP News
- Scientists probe cosmic visitor from deep space, come up empty in search for alien life Los Angeles Times
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