Overview
- Ground-based ALMA observations measured methanol-to-hydrogen cyanide ratios of about 70 and 120 on two dates, placing 3I/ATLAS among the most methanol‑rich comets observed.
- High‑resolution imaging indicates hydrogen cyanide is emitted mainly from the nucleus, while methanol also comes from detached icy grains in the coma, behavior consistent with hyperactive comets.
- JWST measurements from December 2025 reported in a preprint suggest water highly enriched in deuterium and atypical carbon isotopes, pointing to formation in a very cold environment and possibly 10–12 billion years ago.
- The comet is the third confirmed interstellar object and is now outbound, with a close pass by Jupiter expected around March 15 before it continues toward the outer solar system.
- Researchers emphasize that 3I/ATLAS is a natural, chemically complex comet, and media reports note the ALMA analysis is circulating as an arXiv preprint pending peer review.