Scientists using the James Webb Space Telescope have directly analyzed the surface of a distant super-Earth – and found a dark, airless, Mercury-like world
A rocky planet 49 light-years from Earth has just had its surface read for the first time, and the portrait is bleak. LHS 3844 b, a super-Earth roughly 1.3 times the size of our planet, whips around its small red dwarf star once every 11 hours, locked so that one hemisphere permanently faces the stellar furnace. Using the James Webb Space Telescope, an international team has now captured the mid-infrared glow of that scorched dayside and matched it to a dark, basalt-and-olivine crust with no meaningful atmosphere and no detectable volcanic activity. The result, published in Nature Astronomy in May 2026, marks the first time astronomers have directly identified the mineral makeup of a rocky exoplanet’s surface.
How the team pulled a spectrum from bare rock
Led by Sebastian Zieba and Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg, the researchers pointed JWST’s Mid-Infrared Instrument (MIRI) at LHS 3844 b during secondary eclipses, the brief windows when the planet slips behind its star. By subtracting the star-only signal from the combined star-plus-planet signal, they isolated thermal emission from the planet itself across wavelengths of 5 to 12 micrometers. That spectral range is where silicate minerals leave distinctive fingerprints, and the team compared the extracted spectrum against a library of laboratory-measured rock samples.
The best match pointed to a low-silica surface dominated by basalt and olivine, minerals familiar from Mercury, the Moon, and volcanic ocean floors on Earth, but sharply different from the silica-rich granite that makes up Earth’s continents. According to the study, an Earth-like continental crust composition is explicitly ruled out by the data.
Co-author Renyu Hu of NASA’s Jet Propulsion Laboratory and the California Institute of Technology noted that two surface scenarios remain in play: the dayside could be covered in fresh, solid basalt flows, or it could be blanketed in regolith, a loose layer of pulverized rock created by billions of years of micrometeorite bombardment, much like the powdery gray surface of the Moon. “Both textures produce similar spectral shapes in the mid-infrared, and separating them will require follow-up observations or improved laboratory comparisons,” Hu said in a statement accompanying the study.
No air, no volcanoes, no reprieve
The conclusion that LHS 3844 b has essentially no atmosphere did not start with JWST. In 2019, Kreidberg and colleagues used NASA’s now-retired Spitzer Space Telescope to map the planet’s thermal phase curve, measuring how its brightness changes as different longitudes rotate into view. They found an extreme temperature contrast between the permanent dayside and the frigid nightside, with virtually no heat being carried from one hemisphere to the other. That pattern is the signature of a world with little or no air. The 2019 result, published in Nature, laid the groundwork: because there is no significant atmosphere to muddy the infrared signal, the JWST team could be confident that the light they captured came directly from rock, not gas.
The new study went further by searching for sulfur dioxide, a gas that on Earth and likely on Venus signals active volcanic outgassing. JWST found none above its detection threshold. The team also set upper limits on several other volcanic indicator gases, all consistent with a geologically quiet world. Without eruptions to replenish atmospheric material, and with the star’s radiation steadily stripping away any gas that might accumulate, LHS 3844 b appears doubly sealed in its airless state.
What the data cannot yet tell us
The basalt-versus-regolith question is the most immediate loose end. It matters because the answer encodes history. A regolith surface would suggest billions of years of steady impact gardening with no resurfacing, while relatively fresh basalt could hint at volcanic episodes in the planet’s more recent past. Resolving this will likely require observations at additional wavelengths or with higher spectral resolution.
The volcanic non-detection, while informative, is not proof of a completely dead interior. Low-level activity, or eruptions that paused thousands or millions of years ago, could fall below JWST’s current sensitivity. Subsurface magma may still exist without producing a detectable atmospheric trace. The authors frame their result as a constraint, not a final verdict.
There is also the question of how typical this outcome is. LHS 3844 b orbits a cool M-dwarf star and is tidally locked, a common arrangement for close-in rocky planets around red dwarfs. But different stellar environments, magnetic field strengths, or initial volatile inventories could lead to different fates. Whether dark, stripped, basaltic surfaces are the default for such worlds or whether LHS 3844 b sits at one extreme of a wider range is something only a larger survey of rocky exoplanets can answer.
Why a dead world matters for the search for living ones
At first glance, a scorched, airless rock does not seem like a milestone. But for the field of exoplanet science, LHS 3844 b now serves a role similar to the one hot Jupiters played two decades ago: it is a benchmark. By establishing what a stripped, uninhabitable rocky surface looks like in JWST’s instruments, the team has created a reference point against which future observations of potentially habitable worlds can be compared.
The technique proven here, extracting a mineral spectrum from a planet’s thermal emission during secondary eclipse, is directly applicable to higher-profile targets. The TRAPPIST-1 system, with its seven roughly Earth-sized planets orbiting another nearby red dwarf, is already in JWST’s queue. If any of those worlds retain a substantial atmosphere or show surface compositions richer in silica or volatiles, the contrast with LHS 3844 b will sharpen the picture of what separates a habitable rocky planet from a dead one.
For now, the portrait is stark. LHS 3844 b is a world where proximity to its star has burned away any atmosphere, silenced any volcanism detectable from 49 light-years away, and left behind a dark crust of basalt and olivine baking under permanent starlight. It is the clearest look yet at a rocky exoplanet’s bare surface, and it sets the stage for every comparison that follows.
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*This article was researched with the help of AI, with human editors creating the final content.
