Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet

Guangwei Fu; Luis Welbanks; Drake Deming; Julie Inglis; Michael Zhang; Joshua Lothringer; Jegug Ih; Julianne I Moses; Everett Schlawin; Heather A Knutson; Gregory Henry; Thomas Greene; David K Sing; Arjun B Savel; Eliza M-R Kempton; Dana R Louie; Michael Line; Matt Nixon

doi:10.1038/s41586-024-07760-y

Hydrogen sulfide and metal-enriched atmosphere for a Jupiter-mass exoplanet

Nature. 2024 Aug;632(8026):752-756. doi: 10.1038/s41586-024-07760-y. Epub 2024 Jul 8.

Authors

Guangwei Fu¹, Luis Welbanks², Drake Deming³, Julie Inglis⁴, Michael Zhang⁵, Joshua Lothringer⁶, Jegug Ih³, Julianne I Moses⁷, Everett Schlawin⁸, Heather A Knutson⁴, Gregory Henry⁹, Thomas Greene¹⁰, David K Sing¹¹, Arjun B Savel³, Eliza M-R Kempton³, Dana R Louie¹², Michael Line², Matt Nixon³

Affiliations

¹ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA. [email protected].
² School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.
³ Department of Astronomy, University of Maryland, College Park, MD, USA.
⁴ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
⁵ Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA.
⁶ Department of Physics, Utah Valley University, Orem, UT, USA.
⁷ Space Science Institute, Boulder, CO, USA.
⁸ Steward Observatory, University of Arizona, Tucson, AZ, USA.
⁹ Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA.
¹⁰ NASA Ames Research Center, Moffett Field, CA, USA.
¹¹ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA.
¹² NASA Goddard Space Flight Center, Greenbelt, MD, USA.

PMID: 38977019
DOI: 10.1038/s41586-024-07760-y

Abstract

As the closest transiting hot Jupiter to Earth, HD 189733b has been the benchmark planet for atmospheric characterization^1-3. It has also been the anchor point for much of our theoretical understanding of exoplanet atmospheres from composition⁴, chemistry^5,6, aerosols⁷ to atmospheric dynamics⁸, escape⁹ and modelling techniques^10,11. Previous studies of HD 189733b have detected carbon and oxygen-bearing molecules H₂O and CO (refs. ^12,13) in the atmosphere. The presence of CO₂ and CH₄ has been claimed^14,15 but later disputed^12,16,17. The inferred metallicity based on these measurements, a key parameter in tracing planet formation locations¹⁸, varies from depletion^19,20 to enhancement^21,22, hindered by limited wavelength coverage and precision of the observations. Here we report detections of H₂O (13.4σ), CO₂ (11.2σ), CO (5σ) and H₂S (4.5σ) in the transmission spectrum (2.4-5.0 μm) of HD 189733b. With an equilibrium temperature of about 1,200 K, H₂O, CO and H₂S are the main reservoirs for oxygen, carbon and sulfur. Based on the measured abundances of these three main volatile elements, we infer an atmospheric metallicity of three to five times stellar. The upper limit on the methane abundance at 5σ is 0.1 ppm, which indicates a low carbon-to-oxygen ratio (<0.2), suggesting formation through the accretion of water-rich icy planetesimals. The low oxygen-to-sulfur and carbon-to-sulfur ratios also support the planetesimal accretion formation pathway²³.