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3h ago

ALMA Maps Show Interstellar Comet 3I/ATLAS Is Exceptionally Methanol-Rich

Peer‑reviewed results provide a rare chemical fingerprint from another planetary system.

An artist's impression of 3I/ATLAS is shown as it passes near the Sun, illuminating one side of the comet. On the side of the comet closer to the sun, the methanol gas is shown in blue, with icy dust grains still present in the gas. On the dark side of the comet, the hydrogen cyanide is shown in orange. Credit: NSF/AUI/NSF NRAO/M.Weiss
Researchers found that interstellar object 3I/ATLAS was teeming with an unusually large amount of methanol, a type of alcohol.
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Overview

  • ALMA observations published in The Astrophysical Journal Letters measured methanol-to-HCN production ratios of about 70 and 120, placing 3I/ATLAS among the most methanol-rich comets ever studied.
  • High-resolution mapping indicates distinct release sources, with HCN emitted mainly from the nucleus and methanol released from both the nucleus and sublimating icy grains in the coma.
  • Earlier JWST data showed a carbon dioxide–dominated coma, reinforcing that 3I/ATLAS carries an unusual chemical mix unlike typical Solar System comets.
  • Separate arXiv preprints report extreme deuterium enrichment and atypical carbon and nitrogen isotopic ratios that, if confirmed, would suggest formation in very cold, possibly ancient, low-metallicity conditions.
  • The object is the third confirmed interstellar visitor and is now outbound and fading, limiting further measurements even as teams continue synthesizing multi-instrument datasets.