Authors: Diana Powell | Adina D. Feinstein | Elspeth K. H. Lee | Michael Zhang | Shang‐Min Tsai | Jake Taylor | James Kirk | Taylor J. Bell | J. K. Barstow | Peter Gao | Jacob L. Bean | Jasmina Blecic | K. L. Chubb | Ian J. M. Crossfield | Sean Jordan | Daniel Kitzmann | Sarah E. Moran | Giuseppe Morello | Julianne I. Moses | Luis Welbanks | Jeehyun Yang | Xi Zhang | Eva-Maria Ahrer | Aaron Bello-Arufe | Jonathan Brande | S. L. Casewell | Nicolas Crouzet | Patricio E. Cubillos | Brice-Olivier Demory | Achrène Dyrek | Laura Flagg | Renyu Hu | Julie Inglis | K. Jones | Laura Kreidberg | Mercedes López‐Morales | Pierre-Olivier Lagage | E. A. Meier Valdés | Yamila Miguel | Vivien Parmentier | Anjali A. A. Piette | Benjamin V. Rackham | Michael Radica | Seth Redfield | Kevin B. Stevenson | Hannah R. Wakeford | Keshav Aggarwal | Munazza K. Alam | Natalie M. Batalha | Natasha E. Batalha | Björn Benneke | Zach K. Berta-Thompson | Ryan P. Brady | C. Cáceres | Aarynn L. Carter | Jean-Michel Désert | Joseph Harrington | Nicolas Iro | Michael Line | Joshua D. Lothringer | Ryan J. MacDonald | L. Mancini | Karan Molaverdikhani | Sagnick Mukherjee | Matthew C. Nixon | A. Oza | Ε. Πάλλη | Zafar Rustamkulov | David K. Sing | Maria E. Steinrueck | Olivia Vénot | P. J. Wheatley | S. N. Yurchenko
Source: Nature (article, 2024-01-17)
Field: Chemistry — Spectroscopy

Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b The recent inference of sulfur dioxide (SO<sub>2</sub>) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations<sup>1-3</sup> suggests that photochemistry is a key process in high-temperature exoplanet atmospheres<sup>4</sup>. This is because of the low (<1 ppb) abundance of SO<sub>2</sub> under thermochemical equilibrium compared with that produced from the photochemistry of H<sub>2</sub>O and H<sub>2</sub>S (1-10 ppm)<sup>4-9</sup>. However, the SO<sub>2</sub> inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 μm and, therefore, the detection of other SO<sub>2</sub> absorption bands at different wavelengths is needed to better constrain the SO<sub>2</sub> abundance. Here we report the detection of SO<sub>2</sub> spectral features at 7.7 and 8.5 μm in the 5-12-μm transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)<sup>10</sup>. Our observations suggest an abundance of SO<sub>2</sub> of 0.5-25 ppm (1σ range), consistent with previous findings<sup>4</sup>. As well as SO<sub>2</sub>, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 μm. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1-8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range. Sulfur dioxide ; Infrared ; Chemistry ; Optics ; Physics ; Inorganic chemistry Spectroscopy and Laser Applications ; Atmospheric Ozone and Climate ; Calibration and Measurement Techniques