A weather system that defies the conventional circular shape of storms is one of the most unique phenomena in the solar system. This atmospheric feature is an immense, persistent pattern of clouds that has taken on a near-perfect geometric form. The existence of this stable, multi-sided phenomenon challenges our understanding of how high-speed winds organize themselves in planetary atmospheres.
Identifying the Host Planet
This six-sided atmospheric feature is located on Saturn, the ringed gas giant. The hexagon is permanently situated at the planet’s North Pole, centered at approximately 78 degrees north latitude. This storm system is not a transient event, but a long-lived, high-altitude jet stream that encircles the pole.
The structure was first glimpsed in the early 1980s by the Voyager spacecraft. Decades later, the Cassini orbiter provided detailed views of the feature over its 13-year mission. Cassini confirmed the hexagon’s enduring stability, observing it through Saturn’s long seasonal changes.
Anatomy and Scale of the Phenomenon
The scale of the hexagonal storm dwarfs any storm system found on Earth. The entire structure spans approximately 20,000 miles (30,000 kilometers) across its widest point. This massive size means the hexagon is more than twice the diameter of Earth itself.
The sides of the hexagon are defined by an eastward-moving jet stream with winds that reach speeds of up to 200 miles per hour (320 kilometers per hour). At the center lies a hurricane-like polar vortex. This central eye alone is roughly 50 times larger than the eye of an average hurricane on Earth.
Observations from the Cassini spacecraft revealed the hexagon is not confined only to the uppermost cloud layers. The structure extends vertically at least 180 miles (300 kilometers) above the cloud tops, reaching into Saturn’s stratosphere. This deep vertical extent contributes to the feature’s stability and longevity, anchoring it within the planet’s deep atmosphere.
The appearance of the polar region shifts with the planet’s seasons. During the long polar winter, the area inside the hexagon appeared bluish. As the northern hemisphere approached summer solstice in 2017, the color changed to a hazy, golden hue. This seasonal change is attributed to increased solar radiation, which produces photochemical reactions leading to hydrocarbon smog particles.
Explaining the Hexagonal Geometry
The question of why this enormous jet stream adopts a six-sided shape instead of a typical circle is a complex problem in atmospheric physics. Scientists believe the geometry is a manifestation of a large-scale atmospheric phenomenon known as a Rossby wave. These are natural, planetary-scale waves that form in the atmospheres and oceans of rotating bodies.
On Saturn, the high-speed eastward jet stream flows around the pole, but its path is not a smooth circle. Instead, the flow becomes unstable and develops a standing wave pattern with six distinct peaks and troughs. This six-lobed shape is thought to be the most stable configuration for the winds at this specific latitude and speed on Saturn.
The stability of this geometric pattern is also linked to resonant flow dynamics. This involves the intense, high-speed jet stream interacting with smaller, swirling vortices that form along its edges. These smaller storms effectively “pinch” the main jet stream at six evenly spaced points, forcing the flow into the stable, polygonal boundary.
Laboratory experiments have successfully replicated similar geometric patterns using rotating tanks of fluid. When researchers rotate the fluid at different speeds, polygonal shapes—most commonly a hexagon—naturally emerge. These experiments demonstrate that the combination of differential rotation and fluid instability is a natural mechanism for producing stable, multi-sided patterns in a polar region.