Photochemically produced SO₂ in the atmosphere of WASP-39b

May 2023 • 2023Natur.617..483T

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

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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023Natur.617..487T
• PREPRINT http://arxiv.org/abs/2211.10490
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2023Natur.617..483T
• DATA https://doi.org/10.5281/zenodo.7542781
• DATA https://hst.esac.esa.int/ehst/#/pages/search;bibcode=2023Natur.617..483T
• DATA https://mast.stsci.edu
• ELECTR https://doi.org/10.1038%2Fs41586-023-05902-2