NASA announced on Sept 3, 2013 the results of the study by the Cassini space probe of a superstorm that erupted on Saturn in late 2010. These sorts of storms appear every 30 years or so, but this is the first time the phenomenon was observed at close hand.
“The first hint of the most recent storm first appeared in data from Cassini's radio and plasma wave subsystem on Dec. 5, 2010. Soon after that, it could be seen in images from amateur astronomers and from Cassini's imaging science subsystem. The storm quickly grew to superstorm proportions, encircling the planet at about 30 degrees north latitude for an expanse of nearly 190,000 miles (300,000 kilometers).”
Cassini was able to observe the superstorm with its visual and infrared mapping spectrometer. It noted that ice particles consisting of water, ammonia, and a substance thought to be ammonium hydrosulfide were observed at the top of the storm formation. These findings suggest that water vapor was wafted up from deep inside Saturn’s interior by the storm and combined with the other substances to form ice particles as the temperature dropped.
“In understanding the dynamics of this Saturn storm, researchers realized that it worked like the much smaller convective storms on Earth, where air and water vapor are pushed high into the atmosphere, resulting in the towering, billowing clouds of a thunderstorm. The towering clouds in Saturn storms of this type, however, were 10 to 20 times taller and covered a much bigger area. They are also far more violent than an Earth storm, with models predicting vertical winds of more than about 300 mph (500 kilometers per hour) for these rare giant storms.”
Cassini has been orbiting Saturn since July, 2004 and has been conducting remote surveys of the planet and its various moons.