CaltechAUTHORS
Published April 26, 2023 | Version Published + Supplemental Material
Journal Article Open

Photochemically produced SO₂ in the atmosphere of WASP-39b

Creators

  • 1. ROR icon University of Oxford
  • 2. ROR icon University of California, Riverside
  • 3. ROR icon University of Bern
  • 4. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 5. ROR icon Carnegie Institution for Science
  • 6. ROR icon University of California, Santa Cruz
  • 7. ROR icon Space Science Institute
  • 8. ROR icon University of Exeter
  • 9. ROR icon French National Centre for Scientific Research
  • 10. ROR icon Observatoire de la Côte d'Azur
  • 11. ROR icon University of Cambridge
  • 12. ROR icon Jet Propulsion Lab
  • 13. ROR icon California Institute of Technology
  • 14. ROR icon University of Bristol
  • 15. ROR icon University of Chicago
  • 16. ROR icon University of Montreal
  • 17. ROR icon Arizona State University
  • 18. ROR icon University College London
  • 19. ROR icon Space Research Institute
  • 20. ROR icon University of St Andrews
  • 21. ROR icon Johns Hopkins University
  • 22. ROR icon Laboratory of Astrophysics of Bordeaux
  • 23. ROR icon Leiden University
  • 24. ROR icon Netherlands Institute for Space Research
  • 25. ROR icon Ludwig-Maximilians-Universität München
  • 26. ROR icon Excellence Cluster Origins
  • 27. ROR icon Johns Hopkins University Applied Physics Laboratory
  • 28. ROR icon Indian Institute of Technology Indore
  • 29. ROR icon University of Amsterdam
  • 30. ROR icon Planetary Science Institute
  • 31. ROR icon Princeton University
  • 32. ROR icon Laboratory for Atmospheric and Space Physics
  • 33. ROR icon National Institute of Science Education and Research
  • 34. ROR icon Imperial College London
  • 35. ROR icon Max Planck Institute for Astronomy
  • 36. ROR icon University of Arizona
  • 37. ROR icon Massachusetts Institute of Technology
  • 38. ROR icon Wesleyan University
  • 39. ROR icon Maison de la Simulation
  • 40. ROR icon Dordt College
  • 41. ROR icon Goddard Space Flight Center
  • 42. ROR icon University of Warwick
  • 43. ROR icon Ames Research Center
  • 44. ROR icon University of Colorado Boulder
  • 45. ROR icon New York University Abu Dhabi
  • 46. ROR icon University of Leicester
  • 47. ROR icon University of Kansas
  • 48. ROR icon KU Leuven
  • 49. ROR icon Trinity College Dublin
  • 50. ROR icon University of Central Florida
  • 51. ROR icon University of Maryland, College Park
  • 52. ROR icon Infrared Processing and Analysis Center
  • 53. ROR icon University of Geneva
  • 54. ROR icon Utah Valley University
  • 55. ROR icon Instituto de Astrofísica de Canarias

Abstract

Photochemistry is a fundamental process of planetary atmospheres that regulates the atmospheric composition and stability. 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 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 Mⱼ) gas giant exoplanet orbiting a Sun-like star with an equilibrium temperature of around 1,100 K. The most plausible way of generating SO₂ in such an atmosphere is through photochemical processes. 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 observations with NIRSpec PRISM (2.7σ) and G395H (4.5σ). 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.

Additional Information

© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. S.-M.T. is supported by the European Research Council advanced grant EXOCONDENSE (no. 740963; principal investigator: R. T. Pierrehumbert). E.K.H.L. is supported by the SNSF Ambizione Fellowship grant (no. 193448). X.Z. is supported by NASA Exoplanet Research grant 80NSSC22K0236. O.V. acknowledges funding from the ANR project 'EXACT' (ANR-21-CE49-0008-01), from the Centre National d'Études Spatiales (CNES) and from the CNRS/INSU Programme National de Planétologie (PNP). L.D. acknowledges support from the European Union H2020-MSCA-ITN-2109 under grant no. 860470 (CHAMELEON) and the KU Leuven IDN/19/028 grant Escher. This work benefited from the 2022 Exoplanet Summer Program at the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a programme financed by the Heising-Simons Foundation. T.D. is an LSSTC Catalyst Fellow. J.K. is an Imperial College Research Fellow. B.V.R. is a 51 Pegasi b Fellow. L.W. is an NHFP Sagan Fellow. A.D.F. is an NSF Graduate Research Fellow. Contributions All authors played a notable role in the JWST Transiting Exoplanet Community Early Release Science Program, including the original proposal, preparatory work, tool development, coordinating meetings and so on. Some specific contributions are listed as follows. S.-M.T., P.G., D.P., X.Z., E.K.H.L. and V.P. designed the project and drafted the article. E.K.H.L. and L.C. performed 3D GCMs. S.-M.T., J.M., E.H., O.V., S.J., R.H., J.Y., K.M., R.B., C.J.B. and A.L. developed and/or performed photochemical models. S.-M.T., J.M., E.H., O.V., S.J., R.H., K.O. and P.T. contributed substantially to model comparisons and chemical analysis. K.L.C. and S.-M.T. compiled the sulfur opacities and E.K.H.L. computed the synthetic spectra. Z.R., D.K.S., J.K., E.S., and A.L.C. reduced and analysed the NIRSpec PRISM data. L.A., H.R.W., M.K.A., S.B., D.G., J.I., T.M.-E. and N.L.W. reduced and analysed the NIRSpec G395H data, with further contributions from J.B. and T.D. B.V.R., J.J.F., S.E.M., S.R., Y.M., K.L.C. and L.D. provided substantial feedback, with E.H. coordinating comments from all other authors, to improve the manuscript. Data availability. The data used in this paper are associated with JWST ERS Program 1366 and are available from the Mikulski Archive for Space Telescopes (https://mast.stsci.edu), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. The chemical networks and abundance output of the photochemical models (ARGO, ATMO, KINETICS and VULCAN) presented in this study are available at https://doi.org/10.5281/zenodo.7542781. Code availability. The codes VULCAN and gCMCRT used in this work to simulate composition and produce synthetic spectra are publicly available: VULCAN6,78 (https://github.com/exoclime/VULCAN); gCMCRT40 (https://github.com/ELeeAstro/gCMCRT). The authors declare no competing interests.

Attached Files

Published - 41586_2023_Article_5902.pdf

Supplemental Material - 41586_2023_5902_Fig10_ESM.jpg

Supplemental Material - 41586_2023_5902_Fig11_ESM.jpg

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Supplemental Material - 41586_2023_5902_Tab1_ESM.jpg

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Additional details

Identifiers

PMCID
PMC10191860
Eprint ID
122466
Resolver ID
CaltechAUTHORS:20230725-857082000.38

Related works

Describes
10.5281/zenodo.7542781 (DOI)

Funding

NASA
JWST-ERS-01366
European Research Council (ERC)
740963
Swiss National Science Foundation (SNSF)
193448
NASA
80NSSC22K0236
Agence Nationale de la Recherche (ANR)
ANR-21-CE49-0008-01
Centre National d'Études Spatiales (CNES)
Centre National de la Recherche Scientifique (CNRS)
Institut national des sciences de l'Univers (INSU)
Programme National de Planetologie (PNP)
Marie Curie Fellowship
860470
Katholieke Universiteit Leuven
IDN/19/028
Heising-Simons Foundation
51 Pegasi b Fellowship
Large Synoptic Survey Telescope Corporation
Imperial College London
NASA Sagan Fellowship
NSF Graduate Research Fellowship

Dates

Created
2023-08-16
Created from EPrint's datestamp field
Updated
2023-08-16
Created from EPrint's last_modified field

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