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 Hexagon Comes to Light   NASA - January 22, 2012

It is unclear how an unusual hexagonal cloud system that surrounds Saturn's north pole was created, keeps its shape, or how long it will last. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it elsewhere in the Solar System. Although its infrared glow was visible previously to the Cassini spacecraft now orbiting Saturn, in 2009 the mysterious hexagonal vortex became fully illuminated by sunlight for the first time during the Cassini's visit. Since then, Cassini has imaged the rotating hexagon in visible light enough times to create a time-lapse movie. The pole center was not well imaged and has been excluded. This movie shows many unexpected cloud motions, such as waves emanating from the corners of the hexagon. Planetary scientists are sure to continue to study this most unusual cloud formation for quite some time.


  Fluid clue to Saturn's Hexagon   PhysOrg - April 17, 2010
Watch the Video

An unusual hexagonal structure found in Saturn's atmosphere has been recreated in an Oxford laboratory.


Saturn's North Pole Hexagon Mystery Solved?   Discovery - April 15, 2010

The hexagon was first detected by the Voyager missions in the 1980s. Infrared mapping of the strange shape by Cassini in 2006 showed that it had survived for at least 25 years. The Oxford researchers made a model of Saturn's North Pole. A slowly-spinning cylinder of water represented Saturn's atmosphere, and a small, rapidly-spinning ring represented a jet stream. They added some fluorescent green dye, and got a pretty well-defined hexagon.

By playing with the speed of the ring, the researchers could make nearly any shape that they wanted. The greater the difference in speed between the water and the ring, the fewer sides the polygon had. The shape seems to be bound by eddies that slowly orbit and confine the inner ring into the polygon. Apparently, these shapes are not uncommon in fluid dynamics and can even be seen in hurricanes. This seems to be an example of a well-known phenomenon in one field being relevant to another in a completely unexpected way. But it takes a while for each community to be aware of the other one's results.

The Oxford researchers made a model of Saturn's North Pole. A slowly-spinning cylinder of water represented Saturn's atmosphere, and a small, rapidly-spinning ring represented a jet stream. They added some fluorescent green dye, and got a pretty well-defined hexagon.

By playing with the speed of the ring, the researchers could make nearly any shape that they wanted. The greater the difference in speed between the water and the ring, the fewer sides the polygon had. The shape seems to be bound by eddies that slowly orbit and confine the inner ring into the polygon.

Apparently, these shapes are not uncommon in fluid dynamics and can even be seen in hurricanes. This seems to be an example of a well-known phenomenon in one field being relevant to another in a completely unexpected way. But it takes a while for each community to be aware of the other one's results.


Saturn's Hexagon Comes to Light NASA December 14, 2009
It is unclear how an unusual hexagonal cloud system that surrounds Saturn's north pole was created, keeps its shape, or how long it will last. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it elsewhere in the Solar System. Although its infrared glow was visible previously to the Cassini spacecraft now orbiting Saturn, over the past year the mysterious hexagonal vortex became fully illuminated by sunlight for the first time during the Cassini's visit. Since then, Cassini has imaged the rotating hexagon in visible light enough times to create a time-lapse movie. The pole center was not well imaged and has been excluded. This movie shows many unexpected cloud motions, such as waves emanating from the corners of the hexagon. Planetary scientists are sure to continue to study this most unusual cloud formation for quite some time.


Saturn's Mysterious Hexagon Emerges from Winter Darkness   Science Daily - December 10, 2009
After waiting years for the sun to illuminate Saturn's north pole again, cameras aboard NASA's Cassini spacecraft have captured the most detailed images yet of the intriguing hexagon shape crowning the planet. The new images of the hexagon, whose shape is the path of a jet stream flowing around the north pole, reveal concentric circles, curlicues, walls and streamers not seen in previous images. The last visible-light images of the entire hexagon were captured by NASA's Voyager spacecraft nearly 30 years ago, the last time spring began on Saturn. After the sunlight faded, darkness shrouded the north pole for 15 years. Much to the delight and bafflement of Cassini scientists, the location and shape of the hexagon in the latest images match up with what they saw in the Voyager pictures


A Mysterious Hexagonal Cloud System on Saturn NASA - March 27, 2007
Why would clouds form a hexagon on Saturn? Nobody is yet sure. Originally discovered during the Voyager flybys of Saturn in the 1980s, nobody has ever seen anything like it anywhere else in the Solar System. If Saturn's South Pole wasn't strange enough with its rotating vortex, Saturn's North Pole might now be considered even stranger. The bizarre cloud pattern is shown above in a recent infrared image taken by the Saturn-orbiting Cassini spacecraft. The images show the stability of the hexagon even 20 years after Voyager. Movies of Saturn's North Pole show the cloud structure maintaining its hexagonal structure while rotating. Unlike individual clouds appearing like a hexagon on Earth, the Saturn cloud pattern appears to have six well defined sides of nearly equal length. Four Earths could fit inside the hexagon. Although full explanations are not yet available, planetary scientists are sure to continue to study this most unusual cloud formation for quite some time.


Methane Rain Formed New Lake on Saturn Moon   National Geographic - January 30, 2009
Methane rains on Saturn's moon Titan may have created a new lake about four times the size of Yellowstone National Park, scientists say. The new lake covers about 13,000 square miles (34,000 square kilometers). It's part of a system of lake like features around Titan's south pole.


Cassini Images Bizarre Hexagon On Saturn Science Daily - March 27, 2007

This nighttime view of Saturn's north pole shows a bizarre six-sided hexagon feature encircling the entire north pole. The red color indicates the amount of 5-micron wavelength radiation, or heat, generated in the warm interior of Saturn that escapes the planet.


Hexagon Spied Around Saturn's Pole National Geographic - March 28, 2007
A new image from NASA's Cassini spacecraft offers the first direct view of a six-sided feature that encircles Saturn's north pole. The 15,000 mile-wide (25,000-kilometer-wide) cloud formation was initially spied during the Voyager missions in the 1980s. But scientists remain baffled by the atmospheric forces driving the unusual feature.




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.

Mysterious Cyclones Seen at Both of Saturn's Poles National Geographic - October 15, 2008

Deep convective structures seen through the atmospheric haze - one of which has punched through to a higher altitude and created its own little vortex. "Little" is relative - the eye of the storm is surrounded by an outer ring of clouds that measures 2,500 miles (4,000 kilometers) wide. That's about five times the size of the largest cyclones, or hurricanes, on Earth.





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