No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
- 1MPIA, APEx, Germany (zieba@mpia.de)
- 2Leiden Observatory, Leiden University, Leiden, The Netherlands
- 3Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, Gif-sur-Yvette, France
- 4Astrobiology Research Unit, University of Liège, Liège, Belgium
- 5Department of Astronomy, University of Texas at Austin, Austin, TX, USA
- 6Department of Earth and Planetary Sciences, Stanford University, Stanford, CA, USA
- 7Department of Astronomy, Boston University, Boston, MA, USA
- 8The Institute for Astrophysical Research, Boston University, Boston, MA, USA
- 9Department of Atmospheric and Oceanic Sciences, Peking University, Beijing, People’s Republic of China
- 10Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, France
- 11Astrobiology Program, Department of Astronomy, University of Washington, Seattle, WA, USA
- 12NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team, University of Washington, Seattle, WA, USA
- 13School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
- 14Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- 15Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- 16Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Pessac, France
- 17Observatoire Astronomique de l’Université de Genève, Versoix, Switzerland
- 18Centre Vie dans l’Univers, Université de Genève, Geneva, Switzerland
- 19NASA Goddard Space Flight Center, Greenbelt, MD, USA
- 20Sellers Exoplanet Environments Collaboration, NASA Goddard Space Flight Center, Greenbelt, MD, USA
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. Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO2) are now detectable. Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO2 in its atmosphere. 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 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 2.6 sigma confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio.
How to cite: Zieba, S., Kreidberg, L., Ducrot, E., Gillon, M., Morley, C., Schaefer, L., Tamburo, P., Koll, D. D. B., Lyu, X., Acuña, L., Agol, E., Iyer, A. R., Hu, R., Lincowski, A. P., Meadows, V. S., Selsis, F., Bolmont, E., Mandell, A. M., and Suissa, G.: No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18489, https://doi.org/10.5194/egusphere-egu24-18489, 2024.
