The James Webb Space Telescope (JWST) has dealt a blow to hopes that TRAPPIST-1 d, a rocky planet 40 light-years away, could be an Earth twin. A new study published in The Astrophysical Journal reports that the telescope found no evidence of an atmosphere similar to our own.

Using Webb’s powerful Near-Infrared Spectrograph (NIRSpec), researchers searched for signs of key atmospheric gases—water vapour, methane, and carbon dioxide—but detected none.

“At this point, we can rule out TRAPPIST-1 d from a list of potential Earth twins or cousins,” said lead author Caroline Piaulet-Ghorayeb.

TRAPPIST-1 d is one of seven planets orbiting a cool red dwarf star. It sits near the inner edge of the system’s “Goldilocks zone,” where temperatures could, in theory, allow liquid water to exist. However, it orbits its star at just 2% of Earth’s distance from the Sun, completing a full orbit in only four Earth days.

Scientists say the planet could still have an extremely thin atmosphere like Mars, be shrouded in thick clouds like Venus (hiding gases from detection), or have no atmosphere at all. One major challenge for planets so close to red dwarfs is survival against intense stellar flares, which can strip atmospheres away over time.

Even so, the TRAPPIST-1 system remains a prime target for study. Red dwarfs are the most common type of star in our galaxy, so understanding which of their planets can hold onto an atmosphere is key to the hunt for life beyond Earth.

Webb is already observing other planets in the system—TRAPPIST-1 e, f, g, and h—which orbit farther out and may have better chances of retaining atmospheres. However, their colder temperatures will make detection more difficult.

“All hope is not lost for atmospheres around the TRAPPIST-1 planets,” Piaulet-Ghorayeb said.

NASA officials stress that findings like this help lay the groundwork for future missions, such as the planned Habitable Worlds Observatory, which will take the next big leap in searching for life outside our solar system.