"There’s always something strange going on with Saturn, the solar system’s most photogenic planet – from the famous rings that baffled Galileo 400 years ago to the methane dunes and lakes of its smoggy moon Titan.
In 10 years of cruising Saturn and its vicinity, NASA’s Cassini spacecraft has seen kinks, braids and waves in the rings so high that they cast shadows across the other rings, and the spacecraft’s cameras recently counted 101 geysers of water shooting from a subsurface ocean through cracks in the icy moon Enceladus.
In its latest spins around the ringed planet, Cassini has focused on a lesser known but hardly less mysterious feature of Saturn, an atmospheric phenomenon whose description – the six-sided vortex – is more evocative of Harry Potter or “Star Wars” than your standard weather report.
When the Voyager spacecraft flew past Saturn in 1980 and 1981, they discovered that the planet’s north pole was capped by a gigantic hexagon-shaped storm, the mother of all polar vortexes. It is an immense hurricane four times the size of the Earth
bordered by a jet stream blowing 220 miles per hour.
After the Voyagers left, winter and darkness descended on Saturn’s North. The planet takes 30 years to complete one orbit of the Sun. Cassini arrived at Saturn in 2004, just ahead of spring. Cassini scientists are eager to see how the hexagon vortex evolves as Saturnian spring turns to summer. The spacecraft will be passing directly over the north pole with its cameras pointing down later this month.
Scientists on Earth have been pondering what causes the vortex to take such an unnatural-looking shape.
In 2010, Ana Aguiar of Lisbon University and colleagues pointed out that the position of the hexagon on Saturn corresponded to the latitude of a narrow and very speedy jet stream. They suggested that friction with slower-moving atmosphere on either side of the jet stream would create eddies, miniature hurricanes, that would push the jet stream north and southas it went around the planet, resulting in a wave shape.
In laboratory experiments with rotating fluids, they were able to reproduce the six-sided shape, providing reassurance that there is nothing supernatural going on at Saturn.
The Cassini team hopes to learn more about how the storm works by paying particular attention to the corners of the hexagon.
At the same time, they can study Saturn’s aurora, the ring of northern lights caused by energetic particles guided by Saturn’s magnetic field crashing down into the atmosphere. This curtain of electrical fire comes down right on top of the hexagon, as it turns out.
It’s always something on Saturn."