Overview
- JWST observations revealed methane gas streaming from 3I/ATLAS as it warmed, marking the first methane detection from an interstellar object.
- Mid‑infrared spectra showed the methane emission rising after the comet rounded the Sun, a sign that heating stripped the outer crust and exposed fresh ice below.
- The Subaru Telescope team measured the coma’s carbon dioxide to water ratio on January 7, 2026 using [O I] emission lines and found it lower than earlier space‑telescope estimates.
- Pre‑perihelion readings by JWST and NASA’s SPHEREx saw a CO2‑rich coma, the gas cloud around the nucleus, underscoring that the volatile mix changed over time.
- Researchers say the evolving chemistry fits a layered nucleus with CO2‑rich surface ice and more water at depth, and they plan another JWST look even as the comet grows harder to observe on its way out of the Solar System.