Saturn’s famous hexagon towers above cloudtops
Deborah Byrd in SPACE | September 5, 2018

As wide as 2 Earths – like nothing seen on any other world – Saturn’s hexagon was thought to be a feature of the lower atmosphere, where Saturn’s weather happens. Now there’s evidence it extends high above the cloudtops.


Cassini captured images in 2012 that were used to create this animation of Saturn’s northern polar hexagon.
Image via NASA/JPL-Caltech/SSI/Hampton University/ESA.

Space scientists have been fascinated by the hexagonal feature at Saturn’s north pole since the Voyager mission first discovered it in 1981. The hexagon – a jet stream in Saturn’s atmosphere, moving at some 200 mph (320 km/h) — was believed to be a feature of Saturn’s lower atmosphere, or troposphere, only. Now, however, as the seasons have passed on Saturn, this bizarre hexagon – which is wider than two Earths – appears to have changed. Writing in the peer-reviewed journal Nature Communications on September 3, 2018, scientists said they now have evidence that the hexagon extends to about 180 miles (300 km) above Saturn’s cloudtops, up into this world’s stratosphere, at least during Saturn’s northern spring and summer.

The new work is a long-term study, using data from the Cassini spacecraft, which arrived at Saturn in 2004 and began observing the hexagon in 2006. Cassini’s mission to Saturn ended in 2017, but scientists are still mining the mission’s data (and will be for years to come). Leigh Fletcher of the University of Leicester, U.K., lead author of the new study, said:

The edges of this newly-found vortex appear to be hexagonal, precisely matching a famous and bizarre hexagonal cloud pattern we see deeper down in Saturn’s atmosphere.

While we did expect to see a vortex of some kind at Saturn’s north pole as it grew warmer, its shape is really surprising. Either a hexagon has spawned spontaneously and identically at two different altitudes, one lower in the clouds and one high in the stratosphere, or the hexagon is in fact a towering structure spanning a vertical range of several hundred kilometers.