An artist’s impression of an exoplanet orbiting its star. Credit: NASA/JPL-Caltech
Scientists have discovered a rocky planet that is likely to have an atmosphere — and could be a host for life.
In a paper published this week in Science1, researchers report their observations of helium escaping from the atmosphere of a rocky exoplanet called LHS 1140b. The finding indicates that LHS 1140b has a helium-rich upper atmosphere, supporting previous evidence that small, rocky planets can have atmospheres. And because LHS 1140b is located in the ‘habitable zone’ — the region surrounding a star in which an orbiting planet can maintain liquid water on its surface — the exoplanet could be a feasible site for life.
“It’s been a major goal in the field of exoplanets to find atmospheres on rocky exoplanets,” says Collin Cherubim, an planetary scientist at Harvard University in Cambridge, Massachusetts. He adds that for Earth-like life to exist, an atmosphere, liquid water and a rocky surface are required — and that LHS 1140b could have all three.
However, the study can’t say for sure whether or not water is present on the exoplanet, and doesn’t verify the exact composition of the planet’s inner atmosphere. Researchers also say the results will need replicating in future observations of exoplanets. Nevertheless, the findings constitute an “amazing missing piece of the puzzle” as to whether rocky exoplanets can have atmospheres, says Sara Seager, an astrophysicist at the Massachusetts Institute of Technology in Cambridge.
Helium world
Astronomers have predicted that rocky exoplanets can have atmospheres that regulate climate, act as shields against radiation and enable the presence of liquid water. However, observing exoplanet atmospheres is technically challenging, and researchers have mostly detected airless worlds or those with atmospheres too faint to discern.
Cherubim and his colleagues turned their attention to LHS 1140b, an exoplanet discovered in 2017 that orbits a red-dwarf star roughly 15 parsecs from Earth. They chose this planet because their computational models predicted that it would have escaping helium, and hence an atmosphere.
JWST reveals first evidence of an exoplanet’s surprising chemistry
The team used the Magellan Clay telescope at Las Campanas Observatory in Chile, observing the planet for 6.5 hours — once in 2024 and once in 2025. On both occasions, the team obtained near-infrared absorption spectra of the exoplanet.
Their observations revealed an abundance of helium escaping from the outer atmosphere. The composition of the inner atmosphere, however, remains unclear. Cherubim suspects that this inner atmosphere contains water and other small, oxidized molecules such as carbon dioxide, but this has yet to be verified with experimental data.
