This false-color infrared image shows clouds of large ammonia ice particles dredged up by the powerful storm.
Credit: Cassini
Thermal infrared images of Saturn from the VISIR instrument on the VLT appear at centre and on the right. An amateur visible-light image from Trevor Barry, of Broken Hill, Australia, appears on the left. The images were obtained on Jan. 19, 2011.
Credit: ESO/Univ. of Oxford/T. Barry
MARYLAND: A giant early-spring storm in Saturn's northern hemisphere - so powerful that it stretches around the entire planet - has been detected.
The rare storm has been wreaking havoc for months and shooting plumes of gas high into the planet's atmosphere, according to data from NASA's Cassini spacecraft and a European Southern Observatory ground-based telescope, that have been tracking its progress
"This disturbance in the northern hemisphere of Saturn has created a gigantic, violent and complex eruption of bright cloud material, which has spread to encircle the entire planet," said lead author Leigh Fletcher, a Cassini team scientist at the University of Oxford in the UK.
"Nothing on Earth comes close to this powerful storm. This is only the sixth one to be recorded since 1876, and the last was way back in 1990 - a storm like this is rare,” he said about the study published in the current edition of Science.
Large disturbance in December
Cassini's radio and plasma wave science instrument first detected the large disturbance in December 2010, and amateur astronomers have been watching it ever since through backyard telescopes.
As it rapidly expanded, the storm's core developed into a giant, powerful thunderstorm, producing a 5,000-km-wide dark vortex possibly similar to Jupiter's Great Red Spot. This is the first major storm on Saturn observed by an orbiting spacecraft and studied at thermal infrared wavelengths.
Infrared observations are key because heat tells researchers a great deal about conditions inside the storm, including temperatures, winds, and atmospheric composition. Temperature data were provided by the Very Large Telescope (VLT) on Cerro Paranal in Chile and Cassini's composite infrared spectrometer (CIRS), operated by NASA's Goddard Space Flight Centre in the U.S.
Originating deep in water clouds
"Our new observations show that the storm had a major effect on the atmosphere, transporting energy and material over great distances - creating meandering jet streams and forming giant vortices - and disrupting Saturn's seasonal [weather patterns]," said co-author Glenn Orton, based at NASA's Jet Propulsion Laboratory (JPL) in California.
The storm may have originated deep down in the water clouds where a phenomenon similar to a thunderstorm drove the creation of a giant convective plume: just as hot air rises in a heated room, this mass of gas headed upwards and punched through Saturn's usually serene upper atmosphere.
These huge disturbances interact with the circulating winds moving east and west and cause dramatic temperature changes high up in the atmosphere.
