Posted on AASNova, an aggregator for publications of AAS (the American Astronomical Society):
https://aasnova.org/2026/01/28/monthly-roundup-interstellar-visitor-3i-atlas/
Kerry Hensley, Monthly Roundup: Interstellar Visitor 3I/ATLAS
Spoiler: it’s a comet. The release of chunks that, themselves, release gas (“hyperactivity”) is a bit odd, but nothing we haven’t seen before from a minority of Solar System comets. And yes, that’s gas: ordinary comet volatiles, just like Solar System comets, except in different amounts. We see subcategories and outliers of Solar System comets give off different gas mixtures, depending on, oh… things we haven’t fully tested out yet, like freshness versus depletion, and their starting formation location during the birth of the Solar System. It’s perfectly understandable that a comet that formed in a different system would have a different gas mixture.