“2.) The largest storm ever known in the Solar System. Like all the planets with atmospheres, Saturn contains its own weather, complete with storms both large and small. While the Cassini mission was able to discover a number of interesting ones on the ringed-world, such as the long-lived polar hexagon and the Southern hemisphere’s Dragon Storm, the most spectacular occurred in 2011, emerging in the northern hemisphere, encircling the entire planet, lapping itself and lasting over 200 days. Images taken as close together as one rotation apart showed that the storm migrated across the Saturnian surface at 60 miles per hour (100 km/hr).

While a handful of storms of this magnitude have been observed every 20–30 years or so dating back to 1876, this was the largest, longest-lived one. In April, we found these storms are suppressed by water vapor in the lower layers of Saturn’s atmosphere. Being heavier than not only hydrogen and helium but also methane, the wet water vapor forms a layer underneath Saturn’s outer exosphere, insulating the inner part of the world. Eventually, the outer layers cool so much that they sink, allowing the inner, wet layers — and storms — to re-emerge. Having developed this picture from Cassini’s true and false-color images, the next major Saturnian storm, predicted for the 2030s, could finally teach us how much water our ringed neighbor contains.”

Launched back in October of 1997, Cassini will take its final plunge into the ringed world it’s been orbiting for over a decade on Friday, September 15th. Before it does, however, it’s worth a look back at the tremendous science that’s come about from the first dedicated mission to venture out to Saturn, including a series of surprises that we had no idea we’d find when we were planning and preparing this mission. Sure, our radioisotope-powered spacecraft was equipped with a lander to investigate the giant moon Titan, and many instruments to analyze the various molecules it would find on Saturn, in its rings, and in its many moons. But the polar hexagon and the central vortex, the largest storm ever seen in the Solar System’s history, a myriad of features in the rings (and their gaps), the cause of the two-toned nature of Iapetus and much, much more all came about not because we were seeking to solve these mysteries, but because we had built a spacecraft capable of looking for more than what we were anticipating.

Take a look back at the top six discoveries of Cassini, with more than 20 images to take your breath away!
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