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Tech & Science
Using the James Webb Space Telescope, astronomers have directly analyzed the surface of an exoplanet for the first time. The planet, known as LHS 3844 b, is a dark, barren, hot rocky world without an atmosphere, resembling Mercury.
Astronomers, using the James Webb Space Telescope, have directly analyzed the surface of an exoplanet for the first time. The planet, known as LHS 3844 b, is classified as a "super-Earth," being about 30% larger than Earth and located approximately 50 light-years away.
Unlike most studies that focus on analyzing the atmospheres of exoplanets, scientists studied the heat emitted directly from the surface of this planet. The results reveal a dark and barren world, devoid of an atmosphere, which may resemble Mercury in nature. Researchers describe this type of direct analysis of a distant planet's geology as "the next step in revealing its nature."
Laura Kreidberg, from the Max Planck Institute for Astronomy in Germany and lead researcher, said in a statement: "Thanks to the incredible sensitivity of the James Webb Space Telescope, we can observe light coming directly from the surface of this distant rocky planet." She added: "We see a dark, hot, barren rock, devoid of any atmosphere."
The planet LHS 3844 b, discovered in 2019, orbits a cool red dwarf star in just 11 hours. It is tidally locked, meaning one side constantly faces the star while the other remains in perpetual darkness. The temperature on the star-facing side reaches about 725 degrees Celsius (1340 degrees Fahrenheit).
In 2023 and 2024, Kreidberg and her team observed three secondary eclipses, moments when the planet moves behind its star. Using the James Webb Telescope's Mid-Infrared Instrument (MIRI), they measured the infrared light emitted from the extremely hot star-facing side and used it to study its surface properties.
By comparing the light signal with known rocks and minerals from Earth, the Moon, and Mars, the team ruled out the presence of an Earth-like crust rich in silica and granite. The study suggests that such crusts typically form through geological processes driven by the presence of water and plate tectonic movement, which recycle rocks and allow lighter minerals to rise to the surface.
Instead, the data points to a surface dominated by basalt, a dark volcanic rock rich in iron and magnesium, commonly found on the surface of the Moon and Mercury. Sebastian Zieba, the study's lead researcher from the Center for Astrophysics at Harvard University and the Smithsonian Institution in Massachusetts, said in a statement: "This planet likely contains only a small amount of water."
Researchers propose two possible explanations for the surface nature. The first is that the surface of LHS 3844 b is relatively young, formed by recent volcanic activity, where the lava has not yet been broken down by micrometeorite impacts. However, volcanic activity is known to release gases such as carbon dioxide or sulfur dioxide, which the MIRI instrument did not detect. The statement read: "If these gases were present in reasonable amounts on the surface of LHS 3844 b, the MIRI instrument would have detected them; however, it found nothing."
The alternative explanation is that the planet is covered by a thick layer of fine-grained dark material, formed over long periods by radiation and meteorite impacts, similar to the Moon or Mercury. Without an atmosphere, its surface is particularly susceptible to this process, known as space weathering, which gradually breaks down rocks and darkens their color.
The study indicates that subsequent observations by the James Webb Space Telescope are planned to improve understanding of the planet's surface properties and determine whether it is solid rock or fragmented material affected by weathering.
