Marked by cloud cover wider than the entire Earth, the Saturn tempest in early 2011 also boasted the "largest and hottest stratospheric vortex ever detected in our solar system" and a mysterious explosion in ethylene production.
But wait, there's more: At one point NASA's Cassini orbiter detected on Saturn an "almost unbelievable" regional temperature spike of 150 degrees Fahrenheit (84 degrees Celsius)—the biggest jump ever recorded in our solar system—NASA announced Thursday.
Video: Evolution of Infrared Hot Spots in Saturn Storm
To get an idea of just how extreme the temperature spike was, imagine teleporting from northern Alaska in winter to the Mojave Desert in summertime—a change of some 150 degrees Fahrenheit (84 degrees Celsius).
"We were quite shocked when we detected the temperature change—nothing like that was ever observed before," said University of Maryland research scientist Brigette Hesman, part of the Cassini team. "It was not at all what we expected."
At its height, the storm—which produced high winds and intense lightning—created a cloud cover that circled the gas giant planet in a band 9,000 miles (14,500 kilometers) wide. (Related: "Saturn Lightning Storm Breaks Solar System Record.")
Accompanying the huge temperature change was the formation of a vast deposit of the hydrocarbon gas ethylene, a byproduct of methane previously seen only in trace amounts in the Saturn atmosphere. How ethylene became so prevalent is a mystery.
"We know this was all caused by a big storm in the lower atmosphere," where temperatures are warm enough for water to condense and form clouds, Hesman said.
But as for how the storm managed to spawn so many oddities? "We'll be studying this one for years to try to figure it out."
(See Saturn pictures.)
Milestone for NASA Saturn Probe
Saturn completes an orbit of the sun every 30 Earth years and has a major storm at roughly the same interval. The 2011 monster storm came ten years early and lasted for more than half a year. It was also the first to be monitored by a sophisticated orbiting satellite.
"I would have to say this is one of the biggest discoveries made so far by Cassini," said Scott Edgington, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. The spacecraft, jointly operated by NASA, the European Space Agency and the Italian Space Agency, arrived at Saturn in 2004 after a seven-year journey.
While the temperature boost was unprecedented, it still left temperatures in the Saturn stratosphere at about -65 degrees F (-54 degrees C). While the inner atmosphere of Saturn can get relatively warm, the stratosphere—roughly the height where long-haul airplanes fly over Earth—is normally extremely cold.
Still, Edgington said, the enormous swing in temperatures may have changed the kind of chemistry taking place—allowing the methane present to evolve into ethylene in a way highly atypical for Saturn.
(Also see: National Geographic magazine on Cassini's mission to Saturn.)
Saturn Vortex Bigger Than Jupiter's Great Red Spot
The size and power of the storm at its strongest was revealed largely through infrared imaging. What that instrument found—and what optical telescopes could not have—is that, as the visible storm spread in cloud deck of Saturn's troposphere, waves of energy shot up hundreds of miles, creating enormous "beacons" of hot air, which pushed into the stratosphere.
Researchers expected the beacons to break up and cool down, but by early 2011 they had instead merged into one enormous vortex that for a brief period was larger than of Jupiter's enormous Great Red Spot.
Edgington said Cassini, with the help of telescopes in Hawaii and Chile, was able to monitor the six-month storm more intensely than any other—and the work is only beginning. On Cassini alone, he said, "we have 12 instruments to use for our research, and we're putting all the data together to get the history of this very unusual event."
The new saturn-storm findings will appear in the November 20 edition of the Astrophysical Journal (available online October 30.)
Author of the National Geographic e-book Mars Landing 2012, Marc Kaufman has been a journalist for more than 35 years, including the past 12 as a science and space writer, foreign correspondent, and editor for the Washington Post. He is also author of First Contact: Scientific Breakthroughs in the Hunt for Life Beyond Earth, published in 2011, and has spoken extensively to crowds across the United States and abroad about astrobiology. He lives outside Washington, D.C., with his wife, Lynn Litterine.