Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Diana Powell; Adina D Feinstein; Elspeth K H Lee; Michael Zhang; Shang-Min Tsai; Jake Taylor; James Kirk; Taylor Bell; Joanna K Barstow; Peter Gao; Jacob L Bean; Jasmina Blecic; Katy L Chubb; Ian J M Crossfield; Sean Jordan; Daniel Kitzmann; Sarah E Moran; Giuseppe Morello; Julianne I Moses; Luis Welbanks; Jeehyun Yang; Xi Zhang; Eva-Maria Ahrer; Aaron Bello-Arufe; Jonathan Brande; S L Casewell; Nicolas Crouzet; Patricio E Cubillos; Brice-Olivier Demory; Achrène Dyrek; Laura Flagg; Renyu Hu; Julie Inglis; Kathryn D Jones; Laura Kreidberg; Mercedes López-Morales; Pierre-Olivier Lagage; Erik A Meier Valdés; Yamila Miguel; Vivien Parmentier; Anjali A A Piette; Benjamin V Rackham; Michael Radica; Seth Redfield; Kevin B Stevenson; Hannah R Wakeford; Keshav Aggarwal; Munazza K Alam; Natalie M Batalha; Natasha E Batalha; Björn Benneke; Zach K Berta-Thompson; Ryan P Brady; Claudio Caceres; Aarynn L Carter; Jean-Michel Désert; Joseph Harrington; Nicolas Iro; Michael R Line; Joshua D Lothringer; Ryan J MacDonald; Luigi Mancini; Karan Molaverdikhani; Sagnick Mukherjee; Matthew C Nixon; Apurva V Oza; Enric Palle; Zafar Rustamkulov; David K Sing; Maria E Steinrueck; Olivia Venot; Peter J Wheatley; Sergei N Yurchenko

doi:10.1038/s41586-024-07040-9

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b

Nature. 2024 Feb;626(8001):979-983. doi: 10.1038/s41586-024-07040-9. Epub 2024 Jan 17.

Authors

Diana Powell^{1

2}, Adina D Feinstein^{3

4}, Elspeth K H Lee⁵, Michael Zhang³, Shang-Min Tsai⁶, Jake Taylor^{7

8

9}, James Kirk¹⁰, Taylor Bell^{11

12}, Joanna K Barstow¹³, Peter Gao¹⁴, Jacob L Bean³, Jasmina Blecic^{15

16}, Katy L Chubb¹⁷, Ian J M Crossfield¹⁸, Sean Jordan¹⁹, Daniel Kitzmann⁴, Sarah E Moran²⁰, Giuseppe Morello^{21

22

23}, Julianne I Moses²⁴, Luis Welbanks²⁵, Jeehyun Yang²⁶, Xi Zhang²⁷, Eva-Maria Ahrer^{28

29}, Aaron Bello-Arufe³⁰, Jonathan Brande¹⁸, S L Casewell³¹, Nicolas Crouzet³², Patricio E Cubillos^{33

34}, Brice-Olivier Demory^{5

35}, Achrène Dyrek³⁶, Laura Flagg^{37

38}, Renyu Hu^{30

39}, Julie Inglis³⁹, Kathryn D Jones⁵, Laura Kreidberg⁴⁰, Mercedes López-Morales⁴¹, Pierre-Olivier Lagage³⁶, Erik A Meier Valdés⁵, Yamila Miguel^{32

42}, Vivien Parmentier⁴³, Anjali A A Piette¹⁴, Benjamin V Rackham^{44

45}, Michael Radica^{8

9}, Seth Redfield^{46

47}, Kevin B Stevenson⁴⁸, Hannah R Wakeford⁴⁹, Keshav Aggarwal⁵⁰, Munazza K Alam¹⁴, Natalie M Batalha⁵¹, Natasha E Batalha⁵², Björn Benneke^{8

9}, Zach K Berta-Thompson⁵³, Ryan P Brady⁵⁴, Claudio Caceres^{55

56

57}, Aarynn L Carter⁵¹, Jean-Michel Désert⁵⁸, Joseph Harrington⁵⁹, Nicolas Iro⁶⁰, Michael R Line²⁵, Joshua D Lothringer⁶¹, Ryan J MacDonald⁶², Luigi Mancini^{33

40

63}, Karan Molaverdikhani^{64

65}, Sagnick Mukherjee⁵¹, Matthew C Nixon⁶⁶, Apurva V Oza³⁰, Enric Palle²², Zafar Rustamkulov⁶⁷, David K Sing^{67

68}, Maria E Steinrueck⁴⁰, Olivia Venot⁶⁹, Peter J Wheatley^{28

29}, Sergei N Yurchenko⁵⁴

Affiliations

¹ Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA. [email protected].
² Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA. [email protected].
³ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
⁴ Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA.
⁵ Center for Space and Habitability, University of Bern, Bern, Switzerland.
⁶ Department of Earth Sciences, University of California, Riverside, Riverside, CA, USA.
⁷ Department of Physics, University of Oxford, Oxford, UK.
⁸ Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal, Montréal, Quebec, Canada.
⁹ Département de Physique, Université de Montréal, Montréal, Quebec, Canada.
¹⁰ Department of Physics, Imperial College London, London, UK.
¹¹ Bay Area Environmental Research Institute, NASA Ames Research Center, Moffett Field, CA, USA.
¹² Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA.
¹³ School of Physical Sciences, The Open University, Milton Keynes, UK.
¹⁴ Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA.
¹⁵ Department of Physics, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
¹⁶ Center for Astro, Particle, and Planetary Physics (CAP3), New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
¹⁷ Centre for Exoplanet Science, University of St Andrews, St Andrews, UK.
¹⁸ Department of Physics & Astronomy, University of Kansas, Lawrence, KS, USA.
¹⁹ Institute of Astronomy, University of Cambridge, Cambridge, UK.
²⁰ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
²¹ Department of Space, Earth and Environment, Chalmers University of Technology, Gothenburg, Sweden.
²² Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain.
²³ INAF - Palermo Astronomical Observatory, Palermo, Italy.
²⁴ Space Science Institute, Boulder, CO, USA.
²⁵ School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
²⁶ Planetary Sciences Section, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
²⁷ Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA.
²⁸ Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK.
²⁹ Department of Physics, University of Warwick, Coventry, UK.
³⁰ Astrophysics Section, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
³¹ School of Physics and Astronomy, University of Leicester, Leicester, UK.
³² Leiden Observatory, University of Leiden, Leiden, The Netherlands.
³³ INAF - Turin Astrophysical Observatory, Pino Torinese, Italy.
³⁴ Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
³⁵ Space and Planetary Sciences, Institute of Physics, University of Bern, Bern, Switzerland.
³⁶ Université Paris-Saclay, CEA, CNRS, AIM, Gif-sur-Yvette, France.
³⁷ Department of Astronomy, Cornell University, Ithaca, NY, USA.
³⁸ Carl Sagan Institute, Cornell University, Ithaca, NY, USA.
³⁹ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
⁴⁰ Max Planck Institute for Astronomy, Heidelberg, Germany.
⁴¹ Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA.
⁴² SRON Netherlands Institute for Space Research, Leiden, The Netherlands.
⁴³ Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, French Riviera, France.
⁴⁴ Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁴⁵ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁴⁶ Astronomy Department, Wesleyan University, Middletown, CT, USA.
⁴⁷ Van Vleck Observatory, Wesleyan University, Middletown, CT, USA.
⁴⁸ Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA.
⁴⁹ School of Physics, University of Bristol, Bristol, UK.
⁵⁰ Indian Institute of Technology Indore, Indore, India.
⁵¹ Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA, USA.
⁵² NASA Ames Research Center, Moffett Field, CA, USA.
⁵³ Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁵⁴ Department of Physics and Astronomy, University College London, London, UK.
⁵⁵ Instituto de Astrofisica, Facultad Ciencias Exactas, Universidad Andres Bello, Santiago, Chile.
⁵⁶ Centro de Astrofisica y Tecnologias Afines (CATA), Santiago, Chile.
⁵⁷ Núcleo Milenio de Formación Planetaria (NPF), Valparaíso, Chile.
⁵⁸ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands.
⁵⁹ Planetary Sciences Group, Department of Physics and Florida Space Institute, University of Central Florida, Orlando, FL, USA.
⁶⁰ Institute of Planetary Research, German Aerospace Center (DLR), Berlin, Germany.
⁶¹ Department of Physics, Utah Valley University, Orem, UT, USA.
⁶² Department of Astronomy, University of Michigan, Ann Arbor, MI, USA.
⁶³ Department of Physics, University of Rome "Tor Vergata", Rome, Italy.
⁶⁴ Universitäts-Sternwarte, Ludwig-Maximilians-Universität München, München, Germany.
⁶⁵ Exzellenzcluster Origins, Garching, Germany.
⁶⁶ Department of Astronomy, University of Maryland, College Park, MD, USA.
⁶⁷ Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA.
⁶⁸ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA.
⁶⁹ Université de Paris Cité and Université Paris-Est Creteil, CNRS, LISA, Paris, France.

Abstract

The recent inference of sulfur dioxide (SO₂) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations^1-3 suggests that photochemistry is a key process in high-temperature exoplanet atmospheres⁴. This is because of the low (<1 ppb) abundance of SO₂ under thermochemical equilibrium compared with that produced from the photochemistry of H₂O and H₂S (1-10 ppm)^4-9. However, the SO₂ inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 μm and, therefore, the detection of other SO₂ absorption bands at different wavelengths is needed to better constrain the SO₂ abundance. Here we report the detection of SO₂ spectral features at 7.7 and 8.5 μm in the 5-12-μm transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)¹⁰. Our observations suggest an abundance of SO₂ of 0.5-25 ppm (1σ range), consistent with previous findings⁴. As well as SO₂, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 μm. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1-8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.