First Atmosphere Detected on Rocky Exoplanet LHS 1140b

Researchers have discovered the first atmosphere surrounding a rocky, Earth-like planet orbiting within the habitable zone of a distant star. This discovery, published in the journal Science, provides the strongest evidence to date that worlds with conditions similar to Earth could exist beyond our solar system.

The Discovery of LHS 1140b

LHS 1140b is a rocky planet located 48 light-years from Earth. It orbits a red star that is smaller and cooler than our Sun. While thousands of exoplanets have been discovered, LHS 1140b is significant because it meets three critical criteria for potential habitability: it is rocky, it is located in the "Goldilocks zone" (the region where temperatures are just right for liquid water to exist), and it has an atmosphere.

Atmospheric Composition

The primary gas detected in the atmosphere of LHS 1140b is helium. While helium alone cannot support terrestrial life, researchers note that other, more life-sustaining gases may be present in the lower layers of the atmosphere. Lead author Dr. Collin Cherubim of Harvard University described the discovery as "a big deal," as it is the first time an atmosphere has been found on a rocky planet in the habitable zone of another star.

Context in the Search for Life

This finding is a critical step toward the discovery of life on other worlds. For a planet to be habitable, it must possess water and be at the correct distance from its star to maintain that water in liquid form. While hundreds of planets have been found in habitable zones, only a few dozen are small and rocky; LHS 1140b is now the first of these to have a confirmed atmosphere.

Comparison to Other Candidates

Search efforts have focused on other candidates, such as K2-18b and the TRAPPIST-1 system. However, these have yielded inconclusive or negative results:

• K2-18b: A sub-Neptune planet where signs of dimethyl sulphide (a gas linked to marine life on Earth) were initially spotted. A 2025 NASA-led reanalysis found the signal too weak to confirm and indicated the gas could form without biology.
• TRAPPIST-1: NASA's James Webb Space Telescope (JWST) has ruled out an Earth-like atmosphere on TRAPPIST-1d, and data for TRAPPIST-1e remains inconclusive.

Technical Discussion and Community Insights

Community discussion surrounding the discovery has highlighted several technical challenges and the technical nature of the planet's environment:

Gravity and Habitability

Some analysts suggest that the planet's mass and radius suggest it is a "Super-Earth," which may result in significantly higher gravity than Earth. One community member calculated that a person weighing 150 lbs on Earth would weigh approximately 280.5 lbs on LHS 1140b, based on the mass and radius provided in NASA's exoplanet catalog.

Stellar Stripping and Tidal Locking

There is ongoing debate regarding the planet's ability to retain an atmosphere despite orbiting a red dwarf star. Red dwarfs are known for intense stellar stripping, which often removes atmospheres from planets in their habitable zones. Additionally, some suggest the planet may be tidally locked, meaning one side always faces the star, which could mean the surface is frozen on the far side and only helium—which has an ultra-low boiling point—remains gaseous.

Future Exploration

The search for life continues with the search for more sophisticated telescopes, such as the proposed solar lens telescope, to better analyze these candidates. Some commenters also discussed the possibility of developing probes to reach LHS 1140b, given its relative proximity of 48 light-years.