Photochemically produced SO2 in the atmosphere of WASP-39b
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 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.
Citation
Tsai , S-M , Lee , E K H , Powell , D , Gao , P , Zhang , X , Moses , J , Hébrard , E , Venot , O , Parmentier , V , Jordan , S , Hu , R , Alam , M K , Alderson , L , Batalha , N M , Bean , J L , Benneke , B , Bierson , C J , Brady , R P , Carone , L , Carter , A L , Chubb , K L , Inglis , J , Leconte , J , Line , M , López-Morales , M , Miguel , Y , Molaverdikhani , K , Rustamkulov , Z , Sing , D K , Stevenson , K B , Wakeford , H R , Yang , J , Aggarwal , K , Baeyens , R , Barat , S , de Val-Borro , M , Daylan , T , Fortney , J J , France , K , Goyal , J M , Grant , D , Kirk , J , Kreidberg , L , Louca , A , Moran , S E , Mukherjee , S , Nasedkin , E , Ohno , K , Rackham , B V , Redfield , S , Taylor , J , Tremblin , P , Visscher , C , Wallack , N L , Welbanks , L , Youngblood , A , Ahrer , E-M , Batalha , N E , Behr , P , Berta-Thompson , Z K , Blecic , J , Casewell , S L , Crossfield , I J M , Crouzet , N , Cubillos , P E , Decin , L , Désert , J-M , Feinstein , A D , Gibson , N P , Harrington , J , Heng , K , Henning , T , Kempton , EM-R , Krick , J , Lagage , P-O , Lendl , M , Lothringer , J D , Mansfield , M , Mayne , N J , Mikal-Evans , T , Palle , E , Schlawin , E , Shorttle , O , Wheatley , P J & Yurchenko , S N 2023 , ' Photochemically produced SO 2 in the atmosphere of WASP-39b ' , Nature , vol. 617 , pp. 483-487 . https://doi.org/10.1038/s41586-023-05902-2
Publication
Nature
Status
Peer reviewed
ISSN
0028-0836Type
Journal article
Rights
Copyright © 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/.
Description
Funding: 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.Collections
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