Overview
- High-resolution ALMA data measured methanol-to-hydrogen cyanide ratios of about 70 and 120, placing 3I/ATLAS among the most methanol-rich comets studied.
- ALMA imaging indicates hydrogen cyanide originates mainly from the nucleus, while methanol is released both from the nucleus and from sublimating icy grains in the coma.
- The results suggest the comet’s ices formed under different conditions than most solar system comets, consistent with earlier JWST detections of a CO2-dominated coma.
- The analysis, based on observations from late 2025, is available as a preprint on arXiv and remains pending peer review.
- 3I/ATLAS is only the third confirmed interstellar object; it was imaged by ESA’s JUICE in February and is now outbound and fading, with a close pass by Jupiter expected on March 15.