Up until now, it was known that two types of storms form on Saturn—small ones that average approximately 2,000 kilometers across and Great White Spots, which can grow to 10 times the size of small ones and have tails that completely circle the planet. The smaller storms tend to last just a few days, Great White Spots, on the other hand, can last for several months. Now, it appears that a third type of storm can form on the planet—mid-size storms.
The researchers report that four such storms were spotted last year—all of them were several thousand kilometers across and all formed in the northern polar region of the planet. They differed dramatically in duration, however—from just a week and a half to seven months. Prior research has shown that storms on Saturn get their start in lower clouds far below the planet's upper cloud cover.
