Photochemically produced SO2 in the atmosphere of WASP-39b

Shang-Min Tsai; Elspeth K H Lee; Diana Powell; Peter Gao; Xi Zhang; Julianne Moses; Eric Hébrard; Olivia Venot; Vivien Parmentier; Sean Jordan; Renyu Hu; Munazza K Alam; Lili Alderson; Natalie M Batalha; Jacob L Bean; Björn Benneke; Carver J Bierson; Ryan P Brady; Ludmila Carone; Aarynn L Carter; Katy L Chubb; Julie Inglis; Jérémy Leconte; Michael Line; Mercedes López-Morales; Yamila Miguel; Karan Molaverdikhani; Zafar Rustamkulov; David K Sing; Kevin B Stevenson; Hannah R Wakeford; Jeehyun Yang; Keshav Aggarwal; Robin Baeyens; Saugata Barat; Miguel de Val-Borro; Tansu Daylan; Jonathan J Fortney; Kevin France; Jayesh M Goyal; David Grant; James Kirk; Laura Kreidberg; Amy Louca; Sarah E Moran; Sagnick Mukherjee; Evert Nasedkin; Kazumasa Ohno; Benjamin V Rackham; Seth Redfield; Jake Taylor; Pascal Tremblin; Channon Visscher; Nicole L Wallack; Luis Welbanks; Allison Youngblood; Eva-Maria Ahrer; Natasha E Batalha; Patrick Behr; Zachory K Berta-Thompson; Jasmina Blecic; S L Casewell; Ian J M Crossfield; Nicolas Crouzet; Patricio E Cubillos; Leen Decin; Jean-Michel Désert; Adina D Feinstein; Neale P Gibson; Joseph Harrington; Kevin Heng; Thomas Henning; Eliza M-R Kempton; Jessica Krick; Pierre-Olivier Lagage; Monika Lendl; Joshua D Lothringer; Megan Mansfield; N J Mayne; Thomas Mikal-Evans; Enric Palle; Everett Schlawin; Oliver Shorttle; Peter J Wheatley; Sergei N Yurchenko

doi:10.1038/s41586-023-05902-2

Photochemically produced SO₂ in the atmosphere of WASP-39b

Nature. 2023 May;617(7961):483-487. doi: 10.1038/s41586-023-05902-2. Epub 2023 Apr 26.

Authors

Shang-Min Tsai^{1

2}, Elspeth K H Lee³, Diana Powell⁴, Peter Gao⁵, Xi Zhang⁶, Julianne Moses⁷, Eric Hébrard⁸, Olivia Venot⁹, Vivien Parmentier¹⁰, Sean Jordan¹¹, Renyu Hu^{12

13}, Munazza K Alam⁵, Lili Alderson¹⁴, Natalie M Batalha¹⁵, Jacob L Bean¹⁶, Björn Benneke¹⁷, Carver J Bierson¹⁸, Ryan P Brady¹⁹, Ludmila Carone²⁰, Aarynn L Carter¹⁵, Katy L Chubb²¹, Julie Inglis^{13

22}, Jérémy Leconte²³, Michael Line¹⁸, Mercedes López-Morales⁴, Yamila Miguel^{24

25}, Karan Molaverdikhani^{26

27}, Zafar Rustamkulov²⁸, David K Sing^{22

28}, Kevin B Stevenson²⁹, Hannah R Wakeford¹⁴, Jeehyun Yang¹², Keshav Aggarwal³⁰, Robin Baeyens³¹, Saugata Barat³¹, Miguel de Val-Borro³², Tansu Daylan³³, Jonathan J Fortney¹⁵, Kevin France³⁴, Jayesh M Goyal³⁵, David Grant¹⁴, James Kirk^{4

36}, Laura Kreidberg³⁷, Amy Louca²⁴, Sarah E Moran³⁸, Sagnick Mukherjee¹⁵, Evert Nasedkin³⁷, Kazumasa Ohno¹⁵, Benjamin V Rackham^{39

40}, Seth Redfield⁴¹, Jake Taylor^{42

17}, Pascal Tremblin⁴³, Channon Visscher^{7

44}, Nicole L Wallack^{5

13}, Luis Welbanks¹⁸, Allison Youngblood⁴⁵, Eva-Maria Ahrer^{46

47}, Natasha E Batalha⁴⁸, Patrick Behr³⁴, Zachory K Berta-Thompson⁴⁹, Jasmina Blecic^{50

51}, S L Casewell⁵², Ian J M Crossfield⁵³, Nicolas Crouzet²⁴, Patricio E Cubillos^{20

54}, Leen Decin⁵⁵, Jean-Michel Désert³¹, Adina D Feinstein¹⁶, Neale P Gibson⁵⁶, Joseph Harrington⁵⁷, Kevin Heng^{26

47}, Thomas Henning³⁷, Eliza M-R Kempton⁵⁸, Jessica Krick⁵⁹, Pierre-Olivier Lagage⁴³, Monika Lendl⁶⁰, Joshua D Lothringer⁶¹, Megan Mansfield⁶², N J Mayne⁶³, Thomas Mikal-Evans³⁷, Enric Palle⁶⁴, Everett Schlawin⁶², Oliver Shorttle¹¹, Peter J Wheatley^{46

47}, Sergei N Yurchenko¹⁹

Affiliations

¹ Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK. shangmit@ucr.edu.
² Department of Earth Sciences, University of California, Riverside, Riverside, CA, USA. shangmit@ucr.edu.
³ Center for Space and Habitability, University of Bern, Bern, Switzerland.
⁴ Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA, USA.
⁵ Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, USA.
⁶ Department of Earth and Planetary Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA.
⁷ Space Science Institute, Boulder, CO, USA.
⁸ University of Exeter, Exeter, UK.
⁹ Université de Paris Cité and Univ. Paris Est Creteil, CNRS, LISA, Paris, France.
¹⁰ Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire Lagrange, Nice, France.
¹¹ Institute of Astronomy, University of Cambridge, Cambridge, UK.
¹² Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
¹³ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
¹⁴ School of Physics, University of Bristol, Bristol, UK.
¹⁵ Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA, USA.
¹⁶ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
¹⁷ Department of Physics and Institute for Research on Exoplanets, Université de Montréal, Montreal, Quebec, Canada.
¹⁸ School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
¹⁹ Department of Physics and Astronomy, University College London, London, UK.
²⁰ Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
²¹ Centre for Exoplanet Science, University of St Andrews, St Andrews, UK.
²² Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD, USA.
²³ Laboratoire d'Astrophysique de Bordeaux, Université de Bordeaux, Pessac, France.
²⁴ Leiden Observatory, University of Leiden, Leiden, the Netherlands.
²⁵ SRON Netherlands Institute for Space Research, Leiden, the Netherlands.
²⁶ Universitäts-Sternwarte München, Ludwig-Maximilians-Universität München, Munich, Germany.
²⁷ Exzellenzcluster Origins, Munich, Germany.
²⁸ Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA.
²⁹ Johns Hopkins Applied Physics Laboratory, Laurel, MD, USA.
³⁰ Indian Institute of Technology Indore, Indore, India.
³¹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, the Netherlands.
³² Planetary Science Institute, Tucson, AZ, USA.
³³ Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA.
³⁴ Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA.
³⁵ School of Earth and Planetary Sciences (SEPS), National Institute of Science Education and Research (NISER), Homi Bhabha National Institute (HBNI), Odisha, India.
³⁶ Department of Physics, Imperial College London, London, UK.
³⁷ Max Planck Institute for Astronomy, Heidelberg, Germany.
³⁸ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA.
³⁹ Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁴⁰ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁴¹ Astronomy Department and Van Vleck Observatory, Wesleyan University, Middletown, CT, USA.
⁴² Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK.
⁴³ Maison de la Simulation, CEA, CNRS, Univ. Paris-Sud, UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France.
⁴⁴ Chemistry and Planetary Sciences, Dordt University, Sioux Center, IA, USA.
⁴⁵ NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁴⁶ Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK.
⁴⁷ Department of Physics, University of Warwick, Coventry, UK.
⁴⁸ NASA Ames Research Center, Moffett Field, CA, USA.
⁴⁹ Department of Astrophysical and Planetary Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁵⁰ Department of Physics, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
⁵¹ Center for Astro, Particle, and Planetary Physics (CAP3), New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
⁵² School of Physics and Astronomy, University of Leicester, Leicester, UK.
⁵³ Department of Physics & Astronomy, University of Kansas, Lawrence, KS, USA.
⁵⁴ INAF - Turin Astrophysical Observatory, Pino Torinese, Italy.
⁵⁵ Institute of Astronomy, Department of Physics and Astronomy, KU Leuven, Leuven, Belgium.
⁵⁶ School of Physics, Trinity College Dublin, Dublin, Ireland.
⁵⁷ Planetary Sciences Group, Department of Physics and Florida Space Institute, University of Central Florida, Orlando, FL, USA.
⁵⁸ Department of Astronomy, University of Maryland, College Park, MD, USA.
⁵⁹ Infrared Processing and Analysis Center (IPAC), California Institute of Technology, Pasadena, CA, USA.
⁶⁰ Département d'Astronomie, Université de Genève, Sauverny, Switzerland.
⁶¹ Department of Physics, Utah Valley University, Orem, UT, USA.
⁶² Steward Observatory, University of Arizona, Tucson, AZ, USA.
⁶³ Department of Physics and Astronomy, Faculty of Environment, Science and Economy, University of Exeter, Exeter, UK.
⁶⁴ Instituto de Astrofísica de Canarias (IAC), Tenerife, Spain.

Abstract

Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability¹. However, no unambiguous photochemical products have been detected in exoplanet atmospheres so far. Recent observations from the JWST Transiting Exoplanet Community Early Release Science Program^2,3 found a spectral absorption feature at 4.05 μm arising from sulfur dioxide (SO₂) in the atmosphere of WASP-39b. WASP-39b is a 1.27-Jupiter-radii, Saturn-mass (0.28 M_J) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of around 1,100 K (ref. ⁴). The most plausible way of generating SO₂ in such an atmosphere is through photochemical processes^5,6. Here we show that the SO₂ distribution computed by a suite of photochemical models robustly explains the 4.05-μm spectral feature identified by JWST transmission observations⁷ with NIRSpec PRISM (2.7σ)⁸ and G395H (4.5σ)⁹. SO₂ is produced by successive oxidation of sulfur radicals freed when hydrogen sulfide (H₂S) is destroyed. The sensitivity of the SO₂ feature to the enrichment of the atmosphere by heavy elements (metallicity) suggests that it can be used as a tracer of atmospheric properties, with WASP-39b exhibiting an inferred metallicity of about 10× solar. We further point out that SO₂ also shows observable features at ultraviolet and thermal infrared wavelengths not available from the existing observations.

Grants and funding

MR/T040866/1/MRC_/Medical Research Council/United Kingdom