Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
Observations of highly irradiated gas giant exoplanets have shown helium escaping from their atmospheres. There is limited evidence for atmospheres on rocky exoplanets, perhaps because they have already escaped. We report near-infrared spectroscopic observations of LHS 1140b, a rocky exoplanet that orbits in the habitable zone of a nearby low-mass star. The transit spectra show absorption by helium escaping from the planet's atmosphere. Helium absorption is detected in 2024 but not in 2025, indicating time-variable atmospheric escape. We interpret these results as indicating an upper atmosphere dominated by helium and depleted in hydrogen, with other volatile species trapped at lower altitudes, consistent with atmospheric fractionation models. No helium absorption is detected for LHS 1140c, a smaller and more strongly irradiated exoplanet in the same system.
Authors
- Mercedes López‐Morales (ORCID: https://orcid.org/0000-0003-3204-8183)
- Robin Wordsworth (ORCID: https://orcid.org/0000-0003-1127-8334)
- Tim Cunningham (ORCID: https://orcid.org/0000-0001-7296-3533)
- Shreyas Vissapragada (ORCID: https://orcid.org/0000-0003-2527-1475)
- Annabella Meech (ORCID: https://orcid.org/0000-0002-7500-7173)
- Michael Zhang (ORCID: https://orcid.org/0000-0002-0659-1783)
- William Misener (ORCID: https://orcid.org/0000-0001-6315-7118)
- Aaron Householder (ORCID: https://orcid.org/0000-0002-5812-3236)
- Nicole L. Wallack (ORCID: https://orcid.org/0000-0003-0354-0187)
- Jason Dittmann (ORCID: https://orcid.org/0000-0001-7730-2240)
- Johanna Teske (ORCID: https://orcid.org/0009-0008-2801-5040)
- David Charbonneau (ORCID: https://orcid.org/0000-0002-9003-484X)
- Leonardo A. Dos Santos (ORCID: https://orcid.org/0000-0002-2248-3838)
- Zifan Lin (ORCID: https://orcid.org/0000-0003-0525-9647)
- Collin Cherubim (ORCID: https://orcid.org/0000-0002-8466-5469)
- Andrew McWilliam
Institutions
- Space Telescope Science Institute (US)
- Planetary Science Institute (US)
- Harvard University (US)
- Johns Hopkins University (US)
- Carnegie Institution for Science (US)
- Washington University in St. Louis (US)
- Johns Hopkins Medicine (US)
- University of Florida (US)
- University of Chicago (US)
- Center for Astrophysics Harvard & Smithsonian (US)
- Carnegie Observatories (US)
- University of Baltimore (US)
- Massachusetts Institute of Technology (US)
Publication Details
- Journal
- Science
- Published
- 2026-07-16
- DOI
- https://doi.org/10.1126/science.aea9708
- Citations
- 1
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 5.89