Webb telescope directly images the rocky surface of the super-Earth LHS 3844 b

A team of astronomers from the Max Planck Institute for Astronomy in Heidelberg and the Harvard-Smithsonian Center for Astrophysics, led by Laura Kreidberg, reported on 5 May 2026 in Nature Astronomy a direct observation of the surface geology of the rocky exoplanet LHS 3844 b. This is the first time that, instead of merely inferring an atmosphere, an analysis has been carried out for a planet outside our solar system that points to the specific composition of the rocks on its surface. According to the paper as published (DOI 10.1038/s41550-026-02860-3), the planet has no detectable atmosphere, while its dayside reaches around 1,000 kelvin, or about 725 degrees Celsius.

LHS 3844 b is a rocky planet roughly 30 percent larger than Earth, orbiting a red dwarf 48.5 light-years from the Sun. A single orbit around its host star takes the planet just under 11 hours, owing to its extreme proximity to the star, only about three stellar radii above its surface. The planet was discovered in 2018 by the TESS mission and has since been observed several times in attempts to detect an atmosphere, but all earlier measurements with the Spitzer telescope gave inconclusive results. The new Webb data, gathered with the MIRI instrument in the mid-infrared between 5 and 12 micrometres, are the first with a spectral signature precise enough to allow an atmosphere to be ruled out and the composition of the rocks to be estimated.

Methodologically, the team observed the thermal emission radiated by the planet just before and after it passed behind its host star, which makes it possible to isolate the signal coming purely from the planet, without contamination by starlight. The resulting spectrum is almost entirely flat, with no absorption features from carbon dioxide, sulphur dioxide or any other gas that would suggest even a thin atmosphere. Because of this uniform emission, the data best match a model of a surface made up of dark, basalt-like rock, possibly weathered by long-term exposure to stellar radiation and micrometeorite impacts.

What this result does NOT confirm

While the find matters because it shows for the first time that direct observation of surface geology is possible for exoplanets, the authors stress that the result does not prove the universal absence of atmospheres on planets orbiting red dwarfs. LHS 3844 b is a specific case, a planet very close to a cool star with an orbital period of just 11 hours, which probably means it long ago lost its atmosphere through powerful plasma bursts and magnetic flares from its host star. Other Webb results, including studies of the TRAPPIST-1 system, suggest that some other rocky worlds in orbit around red dwarfs may have very thin atmospheres, but those findings are still preliminary.

A second important limit is that the conclusion about a basaltic composition is indirect, drawn by comparing the measured spectrum with laboratory measurements of different rock types. The thermal behaviour of basalt and other dark rocks matches the data well enough, but it is possible that another combination of materials, for example a mantle similar to Mercury’s or an altered carbon-rich dark crust, would give a similar spectrum. A firmer conclusion will require further observations with Webb at higher spectral resolution and, longer term, observation of other similar systems to build an empirical catalogue.

The next step for Kreidberg’s team is to attempt a similar measurement of the exoplanet 55 Cancri e, also a rocky super-Earth with a very short orbital period, but around a star more like the Sun. If the absence of an atmosphere were demonstrated there too, that would suggest that very short orbital periods are incompatible with retaining a gaseous envelope, even around stars less aggressive than red dwarfs. Observations of 55 Cancri e are scheduled for July and August 2026, with results expected by the end of that year.

From the standpoint of the search for life outside our solar system, the Kreidberg team’s finding is not encouraging, but nor is it surprising. Red dwarfs make up around 75 percent of all stars in the Milky Way and their habitable zones, the regions in which liquid water on a planet’s surface would be possible, lie very close to the star. If it turns out that close orbits around red dwarfs systematically mean the loss of an atmosphere, that substantially reduces the number of candidates for potentially habitable worlds in our cosmic neighbourhood. On the other hand, systems such as TRAPPIST-1, where rocky planets sit somewhat further from their host star, remain open for closer scrutiny, which is why observation of that system is one of the long-term priorities of the Webb programme.