Interstellar comet 3I/ATLAS reveals high methanol abundance
ALMA observations of comet 3I/ATLAS show exceptionally high levels of methanol, exceeding those in most solar system comets. The comet's icy grains release methanol like miniature comets, providing insights into its formation in another star system.
Using the Atacama Compact Array in Chile during late 2025, researchers tracked the comet's approach to the Sun. They measured methanol-to-hydrogen cyanide ratios of roughly 70 and 120, placing it among the most methanol-rich comets ever observed, while earlier James Webb data had already shown a carbon dioxide-dominated coma.
High-resolution imaging distinguished the molecules' origins. Hydrogen cyanide primarily emanated from the central nucleus, typical of local comets, whereas methanol was released both from the core and from icy particles drifting in the surrounding coma, causing those grains to act like tiny, independent comets as they warmed.
This finding could reshape astrochemical models of how icy bodies form in distant planetary systems, offering a rare comparative baseline for our own solar system's comets. It may also influence future mission planning for interstellar object flybys, as researchers seek to prioritize methanol detection. For the public, such detailed chemical fingerprints could deepen engagement with space science, highlighting the diverse, potentially life-bearing chemistry present across the galaxy.