A massive storm, which could be one of the rare Great White Spot (GWS) outbreaks, has hit Saturn’s northern hemisphere where the central squall measures half the size of earth. While the main spot is about 3,600 miles across the whole system including the tail streaming off to the right is more than 36,000 miles long, according to an image captured by Nasa’s Cassini spacecraft.
The raw, unprocessed image was taken by Cassini on December 24 and received on earth on December 27. It was taken from around one million miles away using a green filter and also shows the dark shadows of the planet’s rings on the disk. Scientists believe the spot appears white because it is made of ammonia ice crystals, the Daily Mail reported.
Storms shoot warm gas up from Saturn’s lower atmosphere and through a thick upper mantle of old, smog-stained ammonia ice. As the gas expands in the upper atmosphere, fresh crystals of ammonia condense on the cooling vapour, forming the white region visible from earth. Bridget Hesman, an assistant research scientist at the University of Maryland, said: “A balloonist floating about 100 km down from the bottom of Saturn’s calm stratosphere would experience an ammonia-ice blizzard.”
The phenomenon — which is a lesser known equivalent of Jupiter’s giant red spot — was first picked up by amateur astronomers in mid December. When the bright white storm emerged on Saturn’s northern hemisphere space enthusiast Anthony Wesley from Australia captured some early images of it.