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,