The power of the Webb telescope, once only a dream, finally brings a clearer picture of an Earth-like exoplanet – but not an especially promising one. The exoplanet TRAPPIST-1 d, despite its similarity to Earth in size, rocky composition, and orbit within the so-called “habitable zone,” proves to be a world without an atmosphere comparable to ours. All traces of water, methane, or carbon dioxide are absent – as confirmed by the latest Webb measurements.

An ambitious plan and an obvious disappointment

In the search for an “Earth twin,” astronomers aimed the Webb telescope at TRAPPIST-1 d — a planet hundreds of thousands of times farther than anything we experience daily, specifically 40.7 light-years away in the Aquarius constellation. The findings are grim: an Earth-like atmosphere is almost completely ruled out.

Three possible scenarios of exoplanet reality

Explanations for this “atmospheric drought” range from moderately optimistic models to almost merciless conclusions:

• Very weak atmosphere — a thin gas envelope, almost undetectable, like that of Mars.


• Dense cloudy environment — high-altitude clouds could obscure the spectroscopic signal, similar to Venus.


• Complete lack of atmosphere — bare rocks without a protective layer, exposed to stellar radiation.

These three scenarios are not mere speculation — the scientific team, led by Caroline Piaulet-Ghorayeb, considers them realistic possibilities.

Orbit, temperature, and star exposure

TRAPPIST-1 d orbits extremely close to its star, at a distance of only 0.0223 AU — just over 2% of Earth's distance from the Sun — and takes just over four days to complete a revolution. This proximity exposes it to strong flares and radiation, which can metastatically drive away the atmosphere. Moreover, the red dwarf TRAPPIST-1 emits XUV radiation comparable to the Sun’s, but it has a stronger effect because its planets orbit much closer. The stellar wind is a thousand times stronger than what Earth experiences. All this means that the planet must be extremely resilient or already abandoned.

What depends on mass, density, and atmosphere?

TRAPPIST-1 d has a mass of 0.388 Earths, a density of about 4.35 g/cm³, and surface gravity just over half of Earth’s — parameters that categorize it as a true rocky world. These attributes suggest it could retain an atmosphere — but the star’s conditions severely limit this.

What do climate and atmospheric development models show?

Simulations indicate two possible outcomes in the foreground: it can retain an atmosphere only under very limited conditions; otherwise — it has none. According to the study “Exo-Venus, Exo-Earth or Exo-Dead?”, TRAPPIST-1 d lies right on the boundary between a Venus-like world, an Earth-like world, and a dead rock.

Webb's legacy: inner planets without atoms?

Experience with planets b and c in the TRAPPIST-1 system points to a similar outcome — Webb has not detected dense, hydrogen-driven atmospheres, suggesting they too are bare or cloud-covered.

The gap between darkness and hope: planets e, f, g, and h

Although the inner planets have disappointed, the outer ones — especially e, f, g, and h — are still contenders for atmospheric detection. They are farther away, somewhat spared from stellar aggression, but colder and harder to observe. Scientists believe these may be able to receive and retain CO₂-based or CO₂-O₂ atmospheres.

Main challenges in observations

The biggest obstacle to detecting atmospheric traces is the brightness and activity of the red dwarf — flares, spots, and changes in brightness can obscure or distort the exoplanet signal. Despite advances in observations, distortions and “stellar contamination” remain a significant problem.

What does all this say about Earth?

The fact that one of the most promising exoplanets — ideally positioned for life — does not have an Earth-like atmosphere shows how exceptional Earth is. Webb’s mission does not flourish in discovering a twin planet — but rather confirms the rarity of conditions suitable for life as we know it.

Looking ahead: research and new technologies

The exploration of the TRAPPIST-1 system is just beginning. New spectrographs and models — along with Webb’s data, simulations, and planned missions with the ELT and other observatories — open the perspective that in the next decade we may learn more, perhaps even recognize biosignatures on distant worlds.