GeminiFocus July 2018 - Page 12

John Blakeslee Science Highlights NIFS sniffs odiferous gas enshrouding our Solar System’s seventh planet; DSSI speckle imaging provides evidence that planets populate binaries with the same frequency as single stars; and a decade of Gemini and Keck adaptive optics imaging sheds light on the triaxial shape and orientation of shiny Psyche while leaving other aspects hidden. Hydrogen Sulfide in the Cloud Tops of Uranus Despite decades of observations, including the landmark visit by Voyager 2 in 1986, the question of whether ammonia (NH 3 ) or hydrogen sulfide (H 2 S) dominates the visible cloud deck on Uranus has remained unresolved. However, recent observations obtained with the Near-infrared Integral Field Spectrometer (NIFS) on Gemini North confirm that hydrogen sulfide, a colorless gas with the distinctive odor of rotten eggs, is a key component of those clouds. The study reporting the long-sought evidence is led by Patrick Irwin of Oxford Uni- versity and appears in the April 23rd issue of Nature Astronomy. The visible cloud deck, which forms by condensation of the gases within the atmosphere of a planet, provides information on the composition of the overall atmospheric reservoir. The NIFS observations, illustrated in Figure 1, sample reflected sunlight from the region immediately above the main visible cloud layer in Uranus’s atmosphere. “The lines we were trying to detect were just barely there, but thanks to the sensitivity of NIFS on Gemini, we have the fingerprint which caught the culprit,” said Irwin. The detection of hydrogen sulfide in the clouds of Uranus contrasts with the inner gas gi- ants, Jupiter and Saturn, where the bulk of the upper clouds are comprised of ammonia ice, 10 GeminiFocus July 2018