Using an infrared instrument, the spacecraft discovered the storm's powerful discharge sent the temperature in Saturn's stratosphere soaring 150 degrees Fahrenheit above normal, the space agency reported Thursday.
"This temperature spike is so extreme it's almost unbelievable, especially in this part of Saturn's atmosphere, which typically is very stable," said Brigette Hesman at NASA's Goddard Spaceflight Center in Greenbelt, Md. "To get a temperature change of the same scale on Earth, you'd be going from the depths of winter in Fairbanks, Alaska, to the height of summer in the Mojave Desert."
First detected by Cassini in Saturn's northern hemisphere Dec. 5, 2010, the storm grew so large that an equivalent storm on Earth would blanket most of North America from north to south and wrap around the planet many times, researchers said.
It was the first storm to be observed at thermal infrared wavelengths, NASA said, allowing scientists to take the temperature of Saturn's atmosphere and to track phenomena that are invisible to the naked eye.