[en] Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a unique opportunity to search for atmospheres on small planets outside the Solar System1. Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO2) are now detectable2,3. Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO2 in its atmosphere4. Here we report the detection of thermal emission from the dayside of TRAPPIST-1 c with the Mid-Infrared Instrument (MIRI) on JWST at 15 µm. We measure a planet-to-star flux ratio of fp/f⁎ = 421 ± 94 parts per million (ppm), which corresponds to an inferred dayside brightness temperature of 380 ± 31 K. This high dayside temperature disfavours a thick, CO2-rich atmosphere on the planet. The data rule out cloud-free O2/CO2 mixtures with surface pressures ranging from 10 bar (with 10 ppm CO2) to 0.1 bar (pure CO2). A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO2-rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than [Formula: see text] Earth oceans of water. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Zieba, Sebastian ; Max-Planck-Institut für Astronomie, Heidelberg, Germany. zieba@mpia.de ; Leiden Observatory, Leiden University, Leiden, The Netherlands. zieba@mpia.de
Kreidberg, Laura ; Max-Planck-Institut für Astronomie, Heidelberg, Germany
Ducrot, Elsa ; Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, Gif-sur-Yvette, France
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophysique, géophysique et océanographie (AGO)
Morley, Caroline; Department of Astronomy, University of Texas at Austin, Austin, TX, USA
Schaefer, Laura ; Department of Earth and Planetary Sciences, Stanford University, Stanford, CA, USA
Tamburo, Patrick; Department of Astronomy, Boston University, Boston, MA, USA ; The Institute for Astrophysical Research, Boston University, Boston, MA, USA
Koll, Daniel D B; Department of Atmospheric and Oceanic Sciences, Peking University, Beijing, People's Republic of China
Lyu, Xintong; Department of Atmospheric and Oceanic Sciences, Peking University, Beijing, People's Republic of China
Acuña, Lorena; Max-Planck-Institut für Astronomie, Heidelberg, Germany ; Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, France
Agol, Eric ; Astrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA ; NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team, University of Washington, Seattle, WA, USA
Iyer, Aishwarya R; School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
Hu, Renyu ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA ; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
Lincowski, Andrew P; Astrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA ; NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team, University of Washington, Seattle, WA, USA
Meadows, Victoria S; Astrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA ; NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team, University of Washington, Seattle, WA, USA
Selsis, Franck ; Laboratoire d'Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Pessac, France
Bolmont, Emeline ; Observatoire Astronomique de l'Université de Genève, Versoix, Switzerland ; Centre Vie dans l'Univers, Université de Genève, Geneva, Switzerland
Mandell, Avi M; NASA Goddard Space Flight Center, Greenbelt, MD, USA ; Sellers Exoplanet Environments Collaboration, NASA Goddard Space Flight Center, Greenbelt, MD, USA
Suissa, Gabrielle ; Astrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA ; NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team, University of Washington, Seattle, WA, USA
This work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programme 2304. M.G. is F.R.S.-FNRS Research Director and acknowledges support from the Belgian Federal Science Policy Office (BELSPO) BRAIN 2.0 (Belgian Research Action through Interdisciplinary Networks) for the project PORTAL no. B2/212/P1/PORTAL (PhOtotrophy on Rocky habiTAble pLanets). V.S.M. and A.P.L. are part of the Virtual Planetary Laboratory Team, which is a member of the NASA Nexus for Exoplanet System Science, and financed through NASA Astrobiology Program grant 80NSSC18K0829. A.R.I. acknowledges support from the NASA FINESST grant 80NSSC21K1846.This work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programme 2304. M.G. is F.R.S.-FNRS Research Director and acknowledges support from the Belgian Federal Science Policy Office (BELSPO) BRAIN 2.0 (Belgian Research Action through Interdisciplinary Networks) for the project PORTAL no. B2/212/P1/PORTAL (PhOtotrophy on Rocky habiTAble pLanets). V.S.M. and A.P.L. are part of the Virtual Planetary Laboratory Team, which is a member of the NASA Nexus for Exoplanet System Science, and financed through NASA Astrobiology Program grant 80NSSC18K0829. A.R.I. acknowledges support from the NASA FINESST grant 80NSSC21K1846.
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