For the first time, astronomers have peered beneath the veil of a distant rocky exoplanet and found a world that bears little resemblance to Earth. Using the James Webb Space Telescope (JWST), scientists have mapped the surface of LHS 3844 b, a super-Earth located just 48.5 light-years away and discovered a dark, airless landscape more akin to Mercury than to our home planet. The findings, published May 4 in Nature Astronomy, mark a milestone in planetary science by revealing the geology of a world beyond our solar system.
LHS 3844 b is a rocky planet about 30% larger than Earth, but its surface is not what scientists expected. Instead of an atmosphere or active geology, the planet appears to be a barren, weathered rock, its surface likely blanketed in basalt or mantle-derived material darkened by eons of space weathering. The discovery is a significant leap forward in understanding the diversity of rocky planets and what makes Earth unique.
The research team, led by Sebastian Zieba—a former PhD student at the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, and now at the Center for Astrophysics | Harvard & Smithsonian—and Laura Kreidberg, MPIA Director and principal investigator, used JWST’s Mid-Infrared Instrument (MIRI) to analyze the planet’s surface. By measuring the infrared light emitted from the planet’s hot dayside, they were able to create a spectrum that revealed the composition of its surface. The results ruled out an Earth-like crust rich in silicate minerals like granite, instead pointing to a surface dominated by volcanic basalt, similar to the Moon or Mercury.
The Dark, Airless World of LHS 3844 b
LHS 3844 b orbits a cool red dwarf star so closely that it completes a full revolution in just 11 hours, making it tidally locked. One side of the planet is perpetually bathed in the star’s intense heat, reaching temperatures of about 1,000 Kelvin (725 degrees Celsius or 1,340 degrees Fahrenheit), while the other remains in eternal darkness. The lack of an atmosphere means the planet is fully exposed to stellar radiation and meteorite impacts, processes that gradually break down surface rocks into fine regolith, or powder.
“Thanks to the amazing sensitivity of JWST, People can detect light coming directly from the surface of this distant rocky planet,” Kreidberg said. “We see a dark, hot, barren rock, devoid of any atmosphere.” The spectrum obtained by MIRI showed that the planet’s surface is consistent with a basalt-rich composition, likely shaped over billions of years by space weathering. Fine dust alone did not match the observations, suggesting the presence of coarser materials like rocks or gravel.
How Scientists Measured a Planet’s Surface from Light-Years Away
Since LHS 3844 b cannot be directly imaged, researchers tracked subtle changes in the combined brightness of the star and planet as it orbits. MIRI measured infrared light between 5 and 12 micrometers, splitting it into smaller wavelength ranges to produce a spectrum. This spectrum was then compared to models based on known rocks and minerals from Earth, the Moon, and Mars, allowing the team to test different surface compositions under the extreme conditions on LHS 3844 b.
The data ruled out an Earth-like crust, which typically forms over long periods through tectonic activity and requires water. Instead, the planet’s surface appears to be dominated by mantle-derived rock, suggesting that Earth-like plate tectonics may not apply to LHS 3844 b. The team also found no evidence of recent volcanic activity, as they detected no trace of sulfur dioxide (SO2), a gas commonly associated with volcanism.
Two Possible Scenarios for the Planet’s Surface
The researchers proposed two scenarios to explain the planet’s surface. The first is that LHS 3844 b is covered in solid basaltic rock that is relatively fresh, indicating recent geological activity such as widespread volcanism. The second scenario suggests that the planet’s surface is shaped over long periods by space weathering, with large regions covered by darkened regolith, similar to the dusty surfaces seen on the Moon or Mercury. This scenario points to a planet that has been geologically inactive for a long time.
“The surface of LHS 3844 b is likely a mix of solid rock and fine dust, darkened by irradiation and meteorite impacts,” Zieba explained. “This makes it more like Mercury or the Moon than Earth.”
What’s Next for LHS 3844 b and JWST
The research team is already planning additional JWST observations to refine their understanding of the planet’s surface. Future measurements will examine how light is emitted and reflected at different angles, allowing scientists to distinguish between solid slabs and loose material. This technique has been successfully used to study asteroids in our solar system and could provide further insights into the nature of LHS 3844 b’s crust.
“We are confident the same technique will allow us to clarify the nature of LHS 3844 b’s crust and, in the future, other rocky exoplanets,” Kreidberg said. The findings not only deepen our understanding of LHS 3844 b but also pave the way for studying the surfaces of other rocky exoplanets, offering a glimpse into the geological diversity of worlds beyond our solar system.
The study, titled “The dark and featureless surface of rocky exoplanet LHS 3844 b from JWST mid-infrared spectroscopy,” was published in Nature Astronomy on May 4, 2026. For more information, visit the Nature Astronomy page or the Center for Astrophysics | Harvard & Smithsonian announcement.
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