Scientists using NASA’s James Webb Space Telescope have achieved an unprecedented view of a planet’s surface beyond our solar system, revealing a hostile world that bears striking similarities to Mercury.
The telescope collected information about a rocky planet roughly 30% bigger than Earth, showing it to be a barren, atmosphere-free world with extreme temperature variations. One hemisphere experiences blazing heat while the opposite side remains frozen in perpetual darkness.
The distant world goes by the name LHS 3844 b, though scientists have nicknamed it Kua’kua—meaning butterfly in a Costa Rican indigenous language. It circles a dim star approximately 49 light-years away from Earth, where one light-year equals 5.9 trillion miles.
“This planet is not a nice place,” stated Laura Kreidberg, who leads the Max Planck Institute for Astronomy in Germany and co-authored the research published in Nature Astronomy this week.
“It’s a hellish, barren rock—much more similar to Mercury than it is to the Earth. There is no trace of an atmosphere. Instead we’re seeing a dark surface, likely old. Picture a bare rock hurtling through space for billions of years. You wouldn’t want to go there,” Kreidberg explained.
Scientists believe the planet’s surface consists of ancient, darkened debris—loose rocky fragments covering solid bedrock that formed over billions of years from constant bombardment by space radiation and tiny meteorite strikes.
The Webb telescope, which launched in 2021 and began operations the following year, has transformed scientists’ ability to study distant worlds. Its powerful infrared sensors can analyze the chemical makeup and atmospheric behavior of exoplanets, including identifying cloud types.
Now Webb allows researchers to examine the geological features and surface materials of these far-off worlds directly, according to Sebastian Zieba, the study’s primary researcher from Harvard & Smithsonian’s Center for Astrophysics in Massachusetts.
“That was very challenging before the James Webb Space Telescope. This, therefore, also puts the Earth and the solar system as a whole into greater context, allowing us to check if processes or surface compositions familiar within the solar system are common around other stars, too,” Zieba explained.
“It’s like we suddenly cleaned our glasses and can see the planets clearly for the first time,” Kreidberg noted.
Kua’kua orbits what astronomers call a red dwarf star—a widespread stellar type with only 15% of our sun’s mass and roughly one-third of its brightness. The planet maintains an incredibly tight orbit, completing one revolution every 11 hours while remaining “tidally locked,” meaning the same side always faces its star, similar to how our moon relates to Earth.
The planet’s sun-facing “dayside” reaches approximately 1,340 degrees Fahrenheit (725 degrees Celsius), while researchers detected no measurable warmth on the permanently dark “nightside.”
Webb’s instruments allowed the team to identify infrared light emanating directly from the planetary surface.
“Different rocks have different spectral fingerprints, just like atmospheres do. Dark volcanic rocks like basalt matched our observations much better than brighter, silica-rich rocks like granite,” Zieba noted.
Both Mercury’s and the moon’s surfaces contain primarily basalt rock.
“On Earth, widespread granite formation is linked to water and plate tectonics,” Zieba said, referencing the geological forces that slowly shift our planet’s massive surface plates. “So if you ever robustly identified granite-like surfaces on an exoplanet, that would not (automatically) mean life, but it would suggest a much more Earth-like geological history compared to other surfaces.”
Researchers also considered whether recent volcanic activity might explain their observations, but their search for volcanic gases like sulfur dioxide came up empty.
The absence of any atmosphere means virtually no shield against harmful stellar radiation or charged particles, plus no possibility for liquid water—widely considered essential for life.
“So overall, this is almost certainly not a habitable world,” Zieba concluded.
