A nearby Earth-sized world has just become even more mysterious
Among the seven Earth-sized planets orbiting the red dwarf TRAPPIST-1, one planet has drawn intense attention from astronomers. That world is TRAPPIST-1e, which sits in the star’s “Goldilocks zone”—the region where temperatures could permit liquid water on the surface, provided the planet has an atmosphere to regulate the climate. Where liquid water can persist, the potential for life follows naturally.
Two new scientific papers present the first detailed observations of the TRAPPIST-1 system via NASA’s James Webb Space Telescope (JWST). These studies, published in the Astrophysical Journal Letters, come from a team led by Sukrit Ranjan of the University of Arizona’s Lunar and Planetary Laboratory. The researchers carefully analyze the existing data and propose several plausible scenarios for what TRAPPIST-1e’s atmosphere and surface might look like.
A third paper offers a note of caution. While early results are promising and mark a significant advance in understanding one of the closest Earth-like exoplanets, Ranjan argues that stronger evidence is needed. He calls for more rigorous testing to confirm whether TRAPPIST-1e truly has an atmosphere and whether the tentative methane signals detected by JWST originate from the planet rather than from its host star.
A Compact Planetary System Close to Home
The TRAPPIST system gets its name from the survey that identified it—the Transiting Planets and Planetesimals Small Telescope project. Located roughly 39 light-years away, this planetary family resembles a scaled-down version of our own solar system, with all seven planets fitting comfortably inside the orbit of Mercury around the star. Each TRAPPIST planet completes an orbit in just a few Earth days, making time ticks in this system move quickly.
"The core idea for TRAPPIST-1e is simple: if it has an atmosphere, it could be habitable," explains Ranjan, an assistant professor at LPL. "But the first crucial question is, does an atmosphere exist at all?"
How Webb Searches for an Atmosphere
To tackle that question, the team used JWST’s powerful Near-Infrared Spectrograph (NIRSpec). They targeted the TRAPPIST system while TRAPPIST-1e was transiting—the planet passing in front of its star. During a transit, some starlight passes through the planet’s atmosphere (if present), and certain wavelengths are absorbed. By measuring this filtered light, astronomers can infer which gases are present. Repeating this process over multiple transits sharpens the picture of the planet’s atmospheric chemistry.
Across four TRAPPIST-1e transits, the team detected faint hints of methane. However, TRAPPIST-1 is an M-dwarf star—much smaller, cooler, and dimmer than the Sun. Because these stars have different physics, Ranjan cautions that interpreting any planetary signal requires care.
"TRAPPIST-1 is an ultracool red dwarf—smaller, cooler, and dimmer than our Sun," he notes. "We saw hints of methane, but the key question remains: is the methane coming from the planet’s atmosphere or from the star itself?"
Investigating the Methane Mystery
To probe this issue, Ranjan and colleagues modeled a range of possible atmospheres for TRAPPIST-1e, emphasizing methane-rich scenarios. They then assessed how likely each scenario would be given the JWST data. In the most plausible cases, TRAPPIST-1e would resemble Titan, Saturn’s methane-rich moon, though this outcome remained quite unlikely overall.
"Based on our latest results, the tentative methane signal is more likely to be star-induced noise," Ranjan explains. "That doesn’t rule out an atmosphere on TRAPPIST-1e, but we need more data to confirm it."
Ranjan also highlights a limitation: JWST, remarkable as it is, was not originally designed to study Earth-sized exoplanets in detail.
"JWST was built before such worlds were even anticipated, and we’re fortunate it can study them at all," he says. "There are only a handful of Earth-sized planets for which we might ever measure atmospheric composition in detail."
New Missions and Techniques on the Horizon
Future observations hold promise for resolving these uncertainties. One exciting project is NASA’s Pandora mission, a small satellite in development for a 2026 launch. Led by Daniel Apai of the University of Arizona’s Steward Observatory, Pandora is dedicated to studying exoplanet atmospheres and their host stars. By monitoring stars before, during, and after planetary transits, Pandora will help scientists separate stellar effects from genuine atmospheric signals.
Meanwhile, the TRAPPIST-1e team is pursuing a broader observing program and applying new analysis methods to finally determine whether the planet has an atmosphere. A key approach is known as the dual-transit method: scientists observe the star during times when both TRAPPIST-1e and TRAPPIST-1b—the system’s innermost, airless planet—transit simultaneously.
"These dual-transit observations will allow us to separate stellar activity from planetary atmospheric signals—if a planet has one," Ranjan says.
But the central question remains: does TRAPPIST-1e have an atmosphere that could render it habitable? The coming years and new missions may finally tip the balance.
Would you bet that TRAPPIST-1e hosts an atmosphere—and possibly life—or do you think the evidence will fade away as more data arrives? Share your thoughts in the comments.
