Cassini has captured something NASA scientists have never seen before: A massive thunder-and-lightning storm that wrapped itself around Saturn creating a seamless ring around the planet. But when the lead portion of the storm finally caught up with itself, it began to lose its steam.
Located at 33 degrees in the northern latitude, NASA first first detected the unprecedented storm in December 2010 using Cassini's radio and plasma wave subsystem and imaging cameras. As the astronomers chronicled its evolution, they started to notice that the turbulent head started to make its way west. This kindled a clockwise-spinning vortex that slowed down. But after a few months, the storm made its way completely around the circumference of the planet, a distance of 190,000 miles (300,000 km).
To put that into perspective, that's roughly the length of 24 Earths placed side-by-side.
Interestingly, the storm, despite its extreme width, is not unlike hurricanes on Earth. Like our storms, it requires the energy provided by warmth; Earth's hurricanes are fed by warm water, whereas Saturn's storms are fed by warm air.
But that's where the differences end. On Earth, a hurricane typically loses its steam when it hits a terrestrial landmass. But on Saturn, where there is no land, it can just keep on going provided its energy needs are met.
That said, the scientists are not entirely sure why the storm sputtered-out when it caught up to itself.
"This thunder-and-lightning storm on Saturn was a beast," said astronomer Kunio Sayanagi through NASA's official statement. "The storm maintained its intensity for an unusually long time. The storm head itself thrashed for 201 days, and its updraft erupted with an intensity that would have sucked out the entire volume of Earth's atmosphere in 150 days. And it also created the largest vortex ever observed in the troposphere of Saturn, expanding up to 7,500 miles [12,000 kilometers] across."
Sayanagi is the study's lead lead researcher and a Cassini imaging team associate at Hampton University in Virginia.
As an aside, the vortex grew to a size comparable to Oval BA on Jupiter; but this storm, along with the Great Red Spot, does not exhibit the same kind of meteorological violence.