Overview
- The multi-day ALMA and Atacama Compact Array campaign in late 2025, now published in The Astrophysical Journal Letters, detected methanol and hydrogen cyanide before the comet slipped behind the Sun.
- The team measured methanol-to-HCN production ratios of about 70 and 120 across two sessions, ranking 3I/ATLAS among the most methanol-rich comets observed.
- Spatial mapping shows hydrogen cyanide emanates chiefly from the nucleus, whereas methanol also escapes from sublimating icy grains in the coma.
- Researchers report this nucleus-versus-coma emission split in molecular sources has been observed in an interstellar object for the first time.
- The composition and outgassing patterns indicate formation conditions different from those that shaped most comets in our Solar System.