Saturn's North Pole Cloud Pattern Hexagon

A persisting hexagonal wave pattern around the north polar vortex in the atmosphere at about 78°N was first noted in the Voyager images. Unlike the north pole, HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor any hexagonal standing wave. NASA reported in November 2006 that the Cassini spacecraft observed a 'hurricane-like' storm locked to the south pole that had a clearly defined eyewall. This observation is particularly notable because eye-wall clouds had not previously been seen on any planet other than Earth.

The straight sides of the northern polar hexagon are each approximately 13,800 km (8,600 mi) long, making them larger than the diameter of the Earth. The entire structure rotates with a period of 10h 39 m 24s, the same period as that of the planet's radio emissions, which is assumed to be equal to the period of rotation of Saturn's interior. The hexagonal feature does not shift in longitude like the other clouds in the visible atmosphere.

The pattern's origin is a matter of much speculation. Most astronomers seem to think it was caused by some standing-wave pattern in the atmosphere; but the hexagon might be a novel aurora. Polygonal shapes have been replicated in spinning buckets of fluid in a laboratory.

Saturn's Hexagon In the News ...

  Hexagon on Saturn: Nasa scientists ponder color-changing north pole   The Guardian - October 27, 2016
Nasa scientists are investigating why the six-sided jet stream at Saturn's north pole has changed color over the past four years. When the region, which is known as the hexagon, was photographed by the Cassini wide-angle camera in 2012 it appeared to be blue. But when the spacecraft passed over it again in 2016 it seemed to have changed to gold.

Bizarre Giant Hexagon on Saturn May Finally Be Explained   Live Science - September 23, 2015
The scenario that best fits Saturn's hexagon involves shallow jets at the cloud level, study team members said. Winds below the cloud level apparently help keep the shape of the hexagon sharp and control the rate at which the hexagon drifts. Different models, such as ones that involve deeper winds or do not take winds lower down into account, do not match Saturn's hexagon well. For instance, they might result in a six-pointed star, or shapes with more or less than six points, or six pairs of storms arranged in a hexagonal pattern.

Saturn's hexagon: An amazing phenomenon   Science Daily - April 8, 2014
An unusual structure with a hexagonal shape surrounding Saturn's north pole was spotted on the planet for the first time thirty years ago. Nothing similar with such a regular geometry had ever been seen on any planet in the solar system. Astronomers have now been able to study and measure the phenomenon and, among other achievements, establish its rotation period. What is more, this period could be the same as that of the planet itself. Saturn is the only planet in the solar system whose rotation time remains unknown.

Bizzare Saturn Vortex Swirls in Stunning New NASA Video   Live Science - December 5, 2013
A NASA probe has captured an amazing video of the huge and mysterious six-sided vortex spinning around Saturn's north pole. Scientists created the new video of Saturn's vortex from 128 images snapped by NASA's Cassini spacecraft in December 2012. It's the highest-resolution movie yet obtained of the giant hexagon, which is about 20,000 miles (32,000 kilometers) wide and has been swirling for at least 30 years, researchers said. The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable. A hurricane on Earth typically lasts a week, but this has been here for decades and who knows - maybe centuries.

Saturn's Poles and Storms

Dragon Storm (dubbed so in September 2004 because of its unusual shape) is a large, bright and complex convective storm in Saturn's southern hemisphere. The Saturnian storm appears to be long-lived and periodically flares up to produce dramatic white plumes which then subside. The storm is a strong source of radio emissions.

Cassini Finds Mysterious New Aurora on Saturn Science Daily - November 12, 2008
Saturn has its own unique brand of aurora that lights up the polar cap, unlike any other planetary aurora known in our solar system. This odd aurora revealed itself to one of the infrared instruments on NASA's Cassini spacecraft.

Beneath the South Pole of Saturn NASA - October 27, 2008
What clouds lurk beneath Saturn's unusual South Pole? To help find out, the robotic Cassini spacecraft currently orbiting Saturn imaged the nether region of the gigantic ringed orb in infrared light. There thick clouds appear dark as they mask much of the infrared light emitted from warmer regions below, while relatively thin clouds appear much lighter. Bands of clouds circle Saturn at several latitudes, while dark ovals indicate many dark swirling storm systems. Surprisingly, a haze of upper level clouds visible towards Saturn's equator disappears near the pole, including over Saturn's strange polar vortex.