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We looked for an atmosphere on TRAPPIST-1d using JWST, but we didn't see any atmospheric absorption. So TRAPPIST-1d is quite different from Earth, despite lying just inside the habitable zone. The planet is either: ➡️ A bare rock. ➡️ Very cloudy. ➡️ Has a thin, Mars-like atmosphere. #Exoplanets 🔭

ESA Space Science@science.esa.int

The TRAPPIST-1 d exoplanet may be Earth-sized 🌍 but it has no Earth-like atmosphere. Webb’s #NIRSpec has found no traces of molecules that are common in Earth’s atmosphere. Read more 👉 www.esa.int/Science_Expl... 🔭 🧪

Dr Ryan MacDonald

@distantworlds.space

13 Aug 2025

The results - led by Caroline Piaulet-Ghorayeb (Université de Montréal / University of Chicago) - are described in: 'Strict Limits on Potential Secondary Atmospheres on the Temperate Rocky Exo-Earth TRAPPIST-1 d' (Piaulet-Ghorayeb et al. 2025): iopscience.iop.org/article/10.3...

Dr Ryan MacDonald

@distantworlds.space

13 Aug 2025

The JWST observations should have seen gases like CO2, H2O, or CH4 for relatively clear thick atmospheres. So the non-detections rule out many classes of rocky planet atmospheres, including: 🌍 Modern and Archean (early) Earth. ♀️ Venus (unless very cloudy). 🔱 Titan.

Dr Ryan MacDonald

@distantworlds.space

The outer planets, TRAPPIST-1e,f,g,h, may still retain atmospheres (even if TRAPPIST-1d is a bare rock). JWST has already observed these planets, so stay tuned for the results!

13/8/25, 5:24 pm0 reposts10 likes

Dwight Williams 🇨🇦

@dewline.bsky.social

13 Aug 2025

It's worth doing the research to find out anyway.

Med Amine Hamidi

@medamine04.bsky.social

13 Aug 2025

TRAPPIST-1 is a very active star, which can make it hard for its planets in the habitable zone to keep an atmosphere. I’m really looking forward to the results.