journal contribution posted on 23.07.2018, 14:53 by Patrick G. J. Irwin, Daniel Toledo, Ryan Garland, Nicholas A. Teanby, Leigh N. Fletcher, Glenn A. Orton, Bruno Bézard
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 ) ×1 0 - 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.
We are grateful to the United Kingdom Science and Technology Facilities Council
for funding this research and also to our support astronomers: Richard McDermid and Chad Trujillo (2009,
2010). The Gemini Observatory is operated by the Association of Universities for Research in Astronomy,
Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science
Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National
Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da ´
322 Ciencia e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnolog ˆ ´ıa e Innovacion Productiva (Argentina). ´
We thank Larry Sromovsky for providing the code used to generate our Rayleigh-scattering opacities. Glenn
Orton was supported by NASA funding to the Jet Propulsion Laboratory, California Institute of Technology.
Leigh Fletcher was supported by a Royal Society Research Fellowship at the University of Leicester
CitationNature Astronomy, 2018, 2, pp. 420–427
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
VersionAM (Accepted Manuscript)
Published inNature Astronomy
PublisherNature Publishing Group
NotesThe file associated with this record is under embargo until 6 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.