Harvard-led study confirms first atmosphere on Earth-like planet in habitable zone

Researchers have identified the first atmosphere surrounding an Earth-like, rocky planet orbiting within the habitable zone of a distant star. The discovery concerns planet LHS 1140b, located 48 light-years from Earth, which orbits a red star smaller and cooler than the Sun. The detected gas is helium, which does not support life, though other gases may be present in the lower atmosphere. Led by Dr Collin Cherubim of Harvard University, the study published in the journal Science provides the strongest evidence yet that worlds with conditions similar to Earth could exist beyond the solar system.

The planet, designated LHS 1140b, is situated 48 light-years from Earth and orbits a red dwarf star that is smaller and cooler than the Sun. While more than 6,000 exoplanets have been discovered to date, only a few dozen are small and rocky like Earth. The habitable zone, often referred to as the Goldilocks zone, represents the orbital distance where temperatures allow for liquid water, a prerequisite for life as we know it. Hundreds of planets have been found in such zones, but none have previously been confirmed to possess an atmosphere while also being rocky and within this critical orbital range.

The specific gas detected in the atmosphere is helium, likely located in the upper atmosphere. While helium does not support life, researchers suggest that other, potentially life-sustaining gases may be present in the lower atmosphere. Dr Collin Cherubim described the discovery as a significant milestone, noting that it is the first time an atmosphere has been found on a rocky planet in the habitable zone of another star. The study, published in the journal Science, underscores the potential for finding worlds with conditions similar to Earth beyond our solar system.

Dr David Charbonneau, also from Harvard University, emphasised the importance of this finding in the broader context of the search for extraterrestrial life. He stated that the study reveals the first atmosphere discovered on a rocky planet in the habitable zone of a star outside our solar system, addressing fundamental questions about whether we are alone. The researchers clarified that while they have not yet discovered life, the presence of an atmosphere is a crucial step towards identifying planets capable of supporting it.

Previous searches for life have included K2-18b, where signs of dimethyl sulphide were initially reported but later reanalysed by NASA in 2025 as too weak to confirm biological origin. The TRAPPIST-1 system remains under scrutiny; the James Webb Space Telescope has ruled out an Earth-like atmosphere for TRAPPIST-1d, while data for TRAPPIST-1e remains inconclusive. The discovery of LHS 1140b’s atmosphere brings scientists a step closer to one of the biggest prizes in science: the discovery of life on another world.

It remains uncertain whether other gases beyond helium are present in the lower atmosphere of LHS 1140b. The presence of an atmosphere does not confirm the presence of life or even liquid water on the planet's surface, and the exact composition of the lower atmosphere remains unknown. However, this finding marks a significant advancement in planetary science, providing a new target for future observations and analysis.