TRAPPIST-1 e lies in its star's habitable zone, where surface water is theoretically possible. Webb's Near-Infrared Spectrograph (NIRSpec) captured light as the planet transited its star, searching for spectral signatures of atmospheric gases. After four such observations, researchers have ruled out some scenarios but stress that further data are essential.
"We're seeing the first signs of what Webb can do with Earth-sized exoplanets," said Nestor Espinoza of the Space Telescope Science Institute, principal investigator for the study. "These initial four observations show us the landscape of possibilities, and we'll refine that picture with additional transits." Two scientific papers describing these findings appear in The Astrophysical Journal Letters.
Scientists conclude the planet no longer has its primary atmosphere, stripped away by stellar flares from its active red dwarf star. Whether a secondary atmosphere has formed remains uncertain. Scenarios under consideration include a Titan-like methane envelope, a global ocean, or localized seas on the planet's permanently sunlit side.
"TRAPPIST-1 is unlike our Sun, so the planets around it may not mirror anything in our solar system," said Cornell University astronomer Nikole Lewis. She emphasized that while a Venus-like or Mars-like carbon dioxide atmosphere is improbable, a modest greenhouse effect could still maintain liquid water.
Because TRAPPIST-1 planets are tidally locked, water - if present - might pool as an ocean or persist in smaller regions where the star remains overhead. Additional Webb observations are now underway, including a new method that compares transits of planets b and e. Since planet b appears to be a bare rock without an atmosphere, signals unique to planet e can be isolated more effectively.
"We're just beginning to see the extraordinary science Webb can achieve," said Ana Glidden of MIT's Kavli Institute, who led the team's atmospheric analysis. "It's amazing to probe starlight around planets 40 light-years away and ask whether conditions could allow life."
The results come from the DREAMS (Deep Reconnaissance of Exoplanet Atmospheres using Multi-instrument Spectroscopy) collaboration of the JWST Telescope Scientist Team. Webb continues to redefine exoplanet science, combining U.S., European, and Canadian expertise in one of the most ambitious space observatories ever launched.
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