Detection of hydrogen sulfide above the clouds in Uranus’s atmosphere

Patrick G.J. Irwin*, Daniel Toledo, Ryan Garland, Nicholas A. Teanby, Leigh N. Fletcher, Glenn A. Orton, Bruno Bézard

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

73 Citations (Scopus)
520 Downloads (Pure)


Visible-to-near-infrared observations indicate that the cloud top of the main cloud deck on Uranus lies at a pressure level of between 1.2 bar and 3 bar. However, its composition has never been unambiguously identified, although it is widely assumed to be composed primarily of either ammonia or hydrogen sulfide (H2S) ice. Here, we present evidence of a clear detection of gaseous H2S above this cloud deck in the wavelength region 1.57-1.59 μm with a mole fraction of 0.4-0.8 ppm at the cloud top. Its detection constrains the deep bulk sulfur/nitrogen abundance to exceed unity (>4.4-5.0 times the solar value) in Uranus's bulk atmosphere, and places a lower limit on the mole fraction of H2S below the observed cloud of (1.0-2.5) × 10-5. The detection of gaseous H2S at these pressure levels adds to the weight of evidence that the principal constituent of 1.2-3-bar cloud is likely to be H2S ice.

Original languageEnglish
Pages (from-to)420-427
Number of pages8
JournalNature Astronomy
Issue number5
Early online date23 Apr 2018
Publication statusPublished - May 2018


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