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. CarterKaty 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

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


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 Program2,3 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 MJ) 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 processes5,6. 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.

Original languageEnglish (US)
Pages (from-to)483-487
Number of pages5
Issue number7961
StatePublished - May 18 2023

ASJC Scopus subject areas

  • General


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