An atmosphere on TRAPPIST-1 d? New observations say maybe

August 24, 2025

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An atmosphere on TRAPPIST-1 d? New observations say maybe

View larger. | Artist’s concept of TRAPPIST-1 d. New observations of the exoplanet by the James Webb Space Telescope show that while there might be an atmosphere on TRAPPIST-1 d, it isn’t an atmosphere like Earth’s. It could, however, have a very thin atmosphere like Mars, or an atmosphere with thick, high-altitude clouds, more like Venus. Or it might not have any atmosphere at all. Image via NASA/ ESA/ CSA/ Joseph Olmsted (STScI)/ Webb Space Telescope.

TRAPPIST-1 d is the 3rd planet in the TRAPPIST-1 planetary system, 40 light-years away. It’s rocky and close in size to Earth. Could it be habitable?
New observations by the Webb space telescope show that it doesn’t have an Earth-like atmosphere. Webb didn’t detect any water, carbon dioxide or methane.
The three primary possibilities for an atmosphere on TRAPPIST-1 d are a very thin atmosphere like Mars, a thick cloudy atmosphere more like Venus or no atmosphere at all.

Meet TRAPPIST-1 d

The exoplanet TRAPPIST-1 d is one of seven rocky planets close in size to Earth orbiting a red dwarf star 40 light-years away. Could it be habitable? NASA’s James Webb Space Telescope has now taken a closer look at this interesting world. A team of researchers, led by the University of Montreal, said on August 13, 2025, that Webb did not find an Earth-like atmosphere with molecules like water, carbon dioxide or methane. There are, however, other atmospheric possibilities for TRAPPIST-1 d. It could have a very thin atmosphere like Mars, or an atmosphere with thick, high-altitude clouds, more like Venus. Or it might not have any atmosphere at all.

The planet, the third out from its star TRAPPIST-1, orbits within the habitable zone of the star. Basically, that is the region where temperatures could allow liquid water on a rocky planet’s surface.

The researchers published their peer-reviewed findings in The Astrophysical Journal on August 13, 2025.

The exoplanet TRAPPIST-1 d intrigues astronomers looking for possibly habitable worlds beyond our solar system because it is similar in size to Earth, rocky, and resides in an area around its star where liquid water on its surface is theoretically possible. (1/5) ? ? ?

— Space Telescope Science Institute (@stsci.edu) 2025-08-14T14:51:46.450Z

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 ?

— Dr Ryan MacDonald (@distantworlds.space) 2025-08-13T17:24:41.100Z

Is there an atmosphere on TRAPPIST-1 d?

TRAPPIST-1 d is the 3rd planet out from its star, TRAPPIST-1. And, like the other six known planets in the system, it is a rocky world, close in size to Earth. It even orbits within the habitable zone. But whether it could actually be habitable depends on whether it has an atmosphere, and if so, what kind of atmosphere.

According to the new Webb observations, if TRAPPIST-1 d does have an atmosphere, it is not Earth-like. Webb didn’t detect any molecules like water, carbon dioxide or methane. Lead author Caroline Piaulet-Ghorayeb, at the University of Chicago and Trottier Institute for Research on Exoplanets at the University of Montreal in Canada, said:

Ultimately, we want to know if something like the environment we enjoy on Earth can exist elsewhere, and under what conditions. While NASA’s James Webb Space Telescope is giving us the ability to explore this question in Earth-sized planets for the first time, at this point we can rule out TRAPPIST-1 d from a list of potential Earth twins or cousins.

Other kinds of atmospheres?

Also, while TRAPPIST-1 d doesn’t seem to have an Earth-like atmosphere, it’s still possible it has some other form of atmosphere that’s harder to detect. As Piaulet-Ghorayeb explained:

There are a few potential reasons why we don’t detect an atmosphere around TRAPPIST-1 d. It could have an extremely thin atmosphere that is difficult to detect, somewhat like Mars. Alternatively, it could have very thick, high-altitude clouds that are blocking our detection of specific atmospheric signatures, something more like Venus. Or, it could be a barren rock, with no atmosphere at all.

The researchers don’t yet know which of those scenarios is the correct one.

A row of 7 small, differently colored planets, with partial view of large reddish sun on left side. — View larger. | A size comparison of the planets of the TRAPPIST-1 system lined up in order of increasing distance from their host star (not to scale). The planetary surfaces are an artist’s concept of what they might look like. Overall, the outer planets are considered the most likely to possibly have atmospheres and even water. Image via NASA/ R. Hurt/ T. Pyle/ ESO.

TRAPPIST-1 b and c

When Webb previously observed the two innermost planets, TRAPPIST-1 b and TRAPPIST-1 c, it found no evidence for atmospheres. Or at best, extremely thin ones. (And TRAPPIST-1 b could possibly have a thin, hazy atmosphere). This perhaps isn’t too surprising, since the planets’ star is a red dwarf. Red dwarfs are highly active, emitting powerful blasts of radiation. In fact, that radiation can strip atmospheres from planets that are too close. So what about TRAPPIST-1 d?

The planet is a bit further out from the star, so according to models of the TRAPPIST-1 system, it could have a better chance of retaining its atmosphere.

What about the outer planets?

There is still hope, however, that one or more of the outer planets in the TRAPPIST-1 system could have an atmosphere more like Earth’s. Indeed, some previous studies have suggested that these – TRAPPIST-1 e, f and g – would be the most likely to hold on to some kind of atmospheres because they are farther from the star.

Some models have even suggested the outer planets of TRAPPIST-1 could be rich in water. Piaulet-Ghorayeb said:

All hope is not lost for atmospheres around the TRAPPIST-1 planets. While we didn’t find a big, bold atmospheric signature for planet d, there is still potential for the outer planets to be holding onto a lot of water and other atmospheric components.

However, since these planets are farther away from the star, they are also colder. This makes detecting any atmospheres more challenging, even for Webb.

Webb is still studying the system, and it will take time for the telescope to be able to complete enough observations of these planets to figure out what they are actually like.

Smiling young woman with long brown hair hanging below her right shoulder. — Caroline Piaulet-Ghorayeb, at the University of Chicago and Trottier Institute for Research on Exoplanets at the University of Montreal in Canada, is the lead author of the new study about TRAPPIST-1 d. Image via University of Chicago.

TRAPPIST-1 and the search for alien life

TRAPPIST-1 is, of course, of great interest due to the possibility that some of its seven planets might be habitable. As such, it is a great place to search for possible evidence of biosignatures: chemical signatures of life. It is an ideal case study for smaller, rocky planets like Earth around red dwarf stars. It could, therefore, help answer the question of how many of these kinds of worlds could actually support life. As Shawn Domagal-Goldman, acting director of the Astrophysics Division at NASA Headquarters in Washington, noted:

As NASA leads the way in searching for life outside our solar system, one of the most important avenues we can pursue is understanding which planets retain their atmospheres, and why. NASA’s James Webb Space Telescope has pushed our capabilities for studying exoplanet atmospheres further than ever before, beyond extreme worlds to some rocky planets, allowing us to begin confirming theories about the kind of planets that may be potentially habitable. This important groundwork will position our next missions, like NASA’s Habitable Worlds Observatory, to answer a universal question: Are we alone?

Bottom line: Is there an atmosphere on TRAPPIST-1 d? New observations from Webb suggest that if there is, it might be more like Mars or Venus. Or it might not exist at all.

Source: Strict Limits on Potential Secondary Atmospheres on the Temperate Rocky Exo-Earth TRAPPIST-1 d

Via Webb Space Telescope

Via University of Montreal

Paul Scott Anderson

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About the Author:

Paul Scott Anderson has had a passion for space exploration that began when he was a child when he watched Carl Sagan’s Cosmos. He studied English, writing, art and computer/publication design in high school and college. He later started his blog The Meridiani Journal in 2005, which was later renamed Planetaria. He also later started the blog Fermi Paradoxica, about the search for life elsewhere in the universe.

While interested in all aspects of space exploration, his primary passion is planetary science and SETI. In 2011, he started writing about space on a freelance basis with Universe Today. He has also written for SpaceFlight Insider and AmericaSpace and has also been published in The Mars Quarterly. He also did some supplementary writing for the iOS app Exoplanet.

He has been writing for EarthSky since 2018, and also assists with proofing and social media.

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