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No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c

Sebastian ZiebaLeiden Observatory, Leiden University, Leiden, The Netherlands. [email protected]Laura KreidbergMax-Planck-Institut für Astronomie, Heidelberg, GermanyElsa DucrotUniversité Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, Gif-sur-Yvette, FranceM. GillonAstrobiology Research Unit, University of Liège, Liège, BelgiumCaroline MorleyDepartment of Astronomy, University of Texas at Austin, Austin, TX, USALaura SchaeferDepartment of Earth and Planetary Sciences, Stanford University, Stanford, CA, USAPatrick TamburoDepartment of Astronomy, Boston University, Boston, MA, USADaniel D. B. KollDepartment of Atmospheric and Oceanic Sciences, Peking University, Beijing, People's Republic of ChinaXintong LyuDepartment of Atmospheric and Oceanic Sciences, Peking University, Beijing, People's Republic of ChinaL. AcuñaAix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, FranceEric AgolAstrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USAAishwarya IyerSchool of Earth and Space Exploration, Arizona State University, Tempe, AZ, USARenyu HuDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USAAndrew LincowskiAstrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USAVictoria MeadowsAstrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USAFranck SelsisLaboratoire d'Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Pessac, FranceÉmeline BolmontCentre Vie dans l'Univers, Université de Genève, Geneva, SwitzerlandAvi MandellNASA Goddard Space Flight Center, Greenbelt, MD, USAGabrielle SuissaAstrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA

2023en

ABI

Annotatsiya

Abstract Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a unique opportunity to search for atmospheres on small planets outside the Solar System 1 . Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO 2 ) are now detectable 2,3 . Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO 2 in its atmosphere 4 . 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 f p / 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, CO 2 -rich atmosphere on the planet. The data rule out cloud-free O 2 /CO 2 mixtures with surface pressures ranging from 10 bar (with 10 ppm CO 2 ) to 0.1 bar (pure CO 2 ). A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6 σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO 2 -rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than $${9.5}_{-2.3}^{+7.5}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mn>9.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>7.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> 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.

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DOI: 10.1038/s41586-023-06232-z

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