Overview

• Two companion papers in The Astrophysical Journal Letters report that four JWST/NIRSpec PRISM transits from 2023 yield features consistent with a secondary, heavy‑gas atmosphere on the Earth‑sized, habitable‑zone planet.
• The team cautions the signal is not yet definitive, noting an atmosphere model fits the spectra but a bare, airless surface remains a viable explanation under current uncertainties.
• Analysis rules out cloudy, primary hydrogen‑dominated atmospheres at better than the 3σ level and disfavors a Venus‑like, carbon‑dioxide‑dominated case, though it is not fully excluded.
• Researchers spent over a year mitigating stellar contamination from TRAPPIST‑1’s starspots and magnetic activity, using methods including Gaussian Process marginalization to isolate potential planetary signals.
• An expanded observing campaign is underway to grow the transit set from four toward nearly 20 and to apply comparative strategies, including pairing measurements with the airless planet TRAPPIST‑1b, to confirm or refute the atmospheric interpretation.