Arriving at Uranus in 1986, Voyager 2 observed a bluish orb with
extremely subtle features. A haze layer hid most of the planet's cloud
features from view. Credit: NASA/JPL-Caltech. › Full image and caption
Even
after decades of observations and a visit by NASA's Voyager 2 spacecraft,
Uranus held on to one critical secret -- the composition of its clouds. Now,
one of the key components of the planet's clouds has finally been verified.
A
global research team that includes Glenn Orton of NASA's Jet Propulsion
Laboratory in Pasadena, California, has spectroscopically dissected the
infrared light from Uranus captured by the 26.25-foot (8-meter) Gemini North
telescope on Hawaii's Mauna Kea. They found hydrogen sulfide, the odiferous gas
that most people avoid, in Uranus' cloud tops. The long-sought evidence was
published in the April 23rd issue of the journal Nature Astronomy.
The
detection of hydrogen sulfide high in Uranus' cloud deck (and presumably
Neptune's) is a striking difference from the gas giant planets located closer
to the Sun -- Jupiter and Saturn -- where ammonia is observed above the clouds,
but no hydrogen sulfide. These differences in atmospheric composition shed
light on questions about the planets' formation and history.
"We've
strongly suspected that hydrogen sulfide gas was influencing the millimeter and
radio spectrum of Uranus for some time, but we were unable to attribute the
absorption needed to identify it positively. Now, that part of the puzzle is
falling into place as well," Orton said.
The
Gemini data, obtained with the Near-Infrared
Integral Field Spectrometer (NIFS), sampled reflected sunlight from a
region immediately above the main visible cloud layer in Uranus' atmosphere.
"While
the lines we were trying to detect were just barely there, we were able to
detect them unambiguously thanks to the sensitivity of NIFS on Gemini, combined
with the exquisite conditions on Mauna Kea," said lead author Patrick Irwin of
the University of Oxford, U.K.
No worries, though, that the odor of hydrogen sulfide would
overtake human senses. According to Irwin, "Suffocation and exposure in the negative 200
degrees Celsius [392 degrees Fahrenheit] atmosphere made of mostly hydrogen,
helium and methane would take its toll long before the smell."
Read
more on the news of Uranus' atmosphere from Gemini Observatory here.
Caltech
in Pasadena, California, manages JPL for NASA.
News Media Contact
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-6215
Gretchen.p.mccartney@jpl.nasa.gov
JoAnna Wendel
NASA Headquarters, Washington
202-358-1003
joanna.r.wendel@nasa.gov
Peter Michaud
Gemini Observatory, Hilo, Hawaii
808-974-2510
pmichaud@gemini.edu
Source: JPL-Caltech/News
