In 1979, Voyager I detected a perfect geometric feature at Saturn’s north pole that, for a long time, was believed to have been caused by a huge storm vortex.1 However, the feature was again spotted in October 2006 by NASA’s Cassini Orbiter spacecraft—this time without the vortex. The unusual geometric feature was that of a perfect hexagon. Even more unusual—it doesn’t rotate with the planet. Images were taken using a visible infrared mapping spectrometer, and are below the outermost ammonia haze ordinarily seen at Saturn’s surface.
Clearly the vortex is not the cause of the hexagon. University of Oxford physicists Ana Claudia Barbosa Aguiar and Peter Read have sought and succeeded in demonstrating how such a feature can form. Placing a 30-liter cylinder of water on a slowly rotating table and placing a small, more rapidly rotating ring within, they produced (illuminated by means of green dye) a “jet stream.” The stream’s geometry changed from circular to polyhedral in shape, depending upon the velocity of the ring (hence, the stream). The faster the ring rotated, the fewer the sides of the polyhedron. Although this might reveal how a hexagon could form, it doesn’t reveal the exact cause as to why one formed on Saturn.
Saturn’s Internal Physics
What is revealed is that Saturn, normally considered a peaceful giant, actually experiences violent forces deeper within. At the southern pole, readily visible, is an immense vortex, with an innermost speed of approximately 300 miles per hour. At the north pole, such a vortex was not expected, in view of the stationary hexagon. However, not only is there a vortex, there are small clouds rotating hundreds of miles per hour above the hexagon. These forces are seemingly caused not by the sun, but rather from deep within the planet. Saturn’s mechanics are attributed to the condensation of water vapor from deep within, releasing huge amounts of heat energy.
As one source2 says, “If there were a bathtub large enough to contain Saturn, it would float on water due to its low density.” What role does this play in the formation and maintenance of Saturn’s “perfect hexagon?” Another source3 says, “What is Saturn’s inner magnetic field?” Indeed, that source also asks, “Why can’t we predict its storms?” and, “What maintains its strange magnetic field?” Learning the answers to these questions should also assist in explaining the mystery of “the perfect hexagon.”
1 Earth experiences its own circular polar vortex of winds. Saturn’s hexagonal feature, however, could hold multiple earth size planets inside it.
3 Cornell University - “Saturn’s Exploration Beyond Cassini-Huygens”
References, Resources, and FYI
The SAO/NASA Astrophysics Data System – “A laboratory model of Saturn’s North Polar Hexagon”
NASA Jet Propulsion Laboratory – “Cassini Images Bizarre Hexagon on Saturn”
American Association for the Advancement of Science - “Saturn’s Strange Hexagon Recreated in the Lab”
To learn more about Saturn, please see “Nothing But the Facts About the Cassini Saturn Mission."