New Analysis Casts Doubt On TRAPPIST‑1e's Methane Signal — Atmosphere Still Unconfirmed

New computer simulations and follow-up analysis of James Webb Space Telescope (JWST) transit data suggest that the earlier tentative detection of methane around TRAPPIST‑1e was likely contaminated by the host star rather than originating from the planet. The work raises fresh uncertainty about whether this promising Earth-size world retains any atmosphere capable of supporting liquid water.

Why TRAPPIST‑1e Attracted Attention

TRAPPIST‑1e is one of seven roughly Earth-sized planets orbiting a cool red dwarf about 40 light-years away. It lies in the system's habitable zone, where surface temperatures could permit liquid water — but that only matters if the planet has an atmosphere to moderate temperatures.

What JWST Initially Saw

In 2023, JWST's Near-Infrared Spectrograph (NIRSpec) recorded four separate transits of TRAPPIST‑1e. Those spectra contained subtle features that some teams interpreted as a nitrogen‑rich atmosphere with methane and little carbon dioxide — a composition reminiscent of Titan in our solar system. Because methane can be associated with biological and complex chemical processes, the hint generated excitement.

New Modeling Shows Methane Would Be Short‑Lived

In the new paper, researchers led by Sukrit Ranjan modeled photochemical lifetimes of methane under TRAPPIST‑1e's conditions. They found methane would be broken down by ultraviolet radiation from the active red dwarf roughly thousands of times faster than it is around Titan. Whereas Titan's methane persists on the order of 10–100 million years, methane on TRAPPIST‑1e would survive only about 200,000 years in these models.

"Based on our most recent work, we suggest that the previously reported tentative hint of an atmosphere is more likely to be 'noise' from the host star," said Sukrit Ranjan, assistant professor at the University of Arizona Lunar and Planetary Laboratory. "However, this does not mean that TRAPPIST‑1e does not have an atmosphere — we just need more data."

Why Stellar Contamination Is Likely

The JWST signals varied noticeably from transit to transit, which is a red flag because a stable planetary atmosphere should produce consistent spectral features. TRAPPIST‑1 is cool enough that some molecular features — including methane — can form in the star's own atmosphere or be produced by stellar activity, mimicking a planetary signature.

Could Geological Processes Replenish Methane?

The study shows that maintaining Titan-like methane concentrations on TRAPPIST‑1e would require implausibly large, continuous sources: nonstop global volcanism, catastrophic methane outgassing from a subsurface reservoir, or constant resurfacing. Even under generous assumptions, these mechanisms fall short of offsetting rapid photochemical destruction.

What Happens Next?

The authors argue that more rigorous analysis and additional observations are needed to determine whether TRAPPIST‑1e has any atmosphere at all. Planned follow-ups include a rare dual-transit observation — when TRAPPIST‑1e and the inner planet TRAPPIST‑1b cross the star together — which could help separate stellar from planetary signals because TRAPPIST‑1b is believed to lack an atmosphere. NASA's Pandora mission, scheduled for launch in 2026, will also observe stars and planets simultaneously to better disentangle stellar and atmospheric features.

The paper describing these results was published on Nov. 3 in The Astrophysical Journal Letters.

Bottom Line

TRAPPIST‑1e remains one of the most interesting potentially habitable exoplanets, but the existence and composition of any atmosphere are still unresolved. Current evidence suggests the JWST methane hint is likely stellar contamination, and the short modeled methane lifetime makes a long‑lived, Titan‑like atmosphere improbable without extraordinary replenishment.