Saturn’s North Polar Hexagon
Published by Astrosyo
Among Saturn’s most puzzling features is the vast hexagon swirling around its north pole.
Originally discovered during the Voyager mission in the 1980s, this giant cloud pattern was later
studied in detail by Cassini-Huygens, revealing a stable, six-sided atmospheric current that has persisted for decades.
False-color Cassini view of Saturn’s hexagon and central vortex.
Credit: NASA/JPL-Caltech/SSI/Hampton University.
What You’re Seeing
Saturn’s north pole is encircled by a massive hexagon-shaped jet stream located at about 78°N latitude.
Each of its six sides measures roughly 14,500 km (9,000 mi)—longer than Earth’s diameter.
The entire pattern spans more than 29,000 km (18,000 mi) across and may extend about 300 km deep into Saturn’s atmosphere.
Winds inside the jet reach speeds of around 320 km/h (200 mph), and the structure rotates with a period matching Saturn’s
internal radio emissions: 10 hours, 39 minutes, 24 seconds.
Unlike other clouds, the hexagon does not drift in longitude, making it one of the most stable weather patterns ever observed on a planet.
Discovery and Observations
The hexagon was first identified in Voyager 1 and 2 images in 1981, and formally described by astronomer
David A. Godfrey in 1987. For years, it remained poorly understood because Saturn’s north pole was in winter darkness.
When sunlight returned in 2009, the Cassini spacecraft captured detailed visible and infrared images,
even recording time-lapse videos of the hexagon’s rotation.
Remarkably, amateur astronomers on Earth have also managed to photograph the hexagon with modest telescopes under good conditions.
Color Changes
Between 2012 and 2016, Cassini observed the hexagon shifting from a blue hue to a golden color.
Scientists believe this change is seasonal: as Saturn’s pole was exposed to sunlight, photochemical reactions produced haze particles that altered the color.
At its center lies a massive polar vortex, a storm larger than Earth, with cloud layers revealed in false-color composites.
Laboratory experiments and fluid dynamics simulations suggest the hexagon forms where winds at different latitudes move at sharply contrasting speeds.
These shear boundaries can naturally give rise to polygonal wave patterns.
Other models point to barotropic instabilities or anticyclonic shielding as stabilizing forces behind Saturn’s enduring six-sided jet stream.
Credits
Image data: NASA/JPL-Caltech/SSI/Hampton University.
Commentary: Astrosyo.