Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
Abstract
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.
Article Details
Journal Info
Science
American Association for the Advancement of Science
Authors (16)
Collin Cherubim
Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA.
Shreyas Vissapragada
Carnegie Science Observatories, Pasadena, CA, USA.
Tim Cunningham
Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA, USA.
Annabella G. Meech
Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA, USA.
David Charbonneau
Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA, USA.
Robin Wordsworth
Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA.
Aaron Householder
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
Johanna Teske
Leonardo A. dos Santos
Nicole L. Wallack
Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA.
William Misener
Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA.
Zifan Lin
Department of Physics, Washington University in St. Louis, St. Louis, MO, USA.
Andrew McWilliam
Carnegie Science Observatories, Pasadena, CA, USA.
Michael Zhang
Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
Jason A. Dittmann
Department of Astronomy, University of Florida, Gainesville, FL, USA.
Mercedes López-Morales
Space Telescope Science Institute, Baltimore, MD, USA.