Saturn Has Two Giant Polygons
For decades, scientists have been captivated by a massive, persistent hexagonal cloud pattern at Saturn's north pole. This six-sided jet stream is an atmospheric marvel, unlike anything seen elsewhere. But it's no longer one-of-a-kind. Recent observations
from the Hubble Space Telescope have revealed a newly forming ten-sided pattern, or decagon, encircling the planet's south pole. This discovery was a surprise, as NASA's Cassini spacecraft extensively studied the southern hemisphere before its mission ended in 2017 and saw no such feature. Its appearance suggests that the conditions in Saturn's atmosphere can create these incredible polygon-shaped waves in both hemispheres.
The Scale Is Almost Unimaginable
These storms are colossal. The northern hexagon is about 32,000 kilometres wide, with each of its six sides being longer than the diameter of Earth. You could fit our entire planet inside it with room to spare. The new southern decagon is even larger, spanning a width of roughly 167,000 kilometres. The hexagon is a jet stream of atmospheric gases whipping around the pole at about 320 kilometres per hour. At the centre of this formation is a polar vortex that resembles a hurricane, but one whose eye is 50 times larger than a typical hurricane on Earth.
They Are Naturally Forming Jet Streams
These incredible shapes are not solid structures but are powerful, meandering jet streams. Scientists believe the hexagonal pattern forms due to a combination of factors. Deep within Saturn's atmosphere, heat transfer creates cyclones and smaller vortices. These smaller storms effectively pinch a powerful, eastward-flowing jet stream, forcing it to warp into a stable, six-sided shape. The vertices of the hexagon rotate at almost the same speed as Saturn itself, which is why the pattern has remained stable for more than 40 years. The newer decagon, however, appears to be a more dynamic and evolving structure, giving scientists a chance to watch a polar polygon in the process of forming.
One Was Discovered Decades Ago, The Other Is New
The northern hexagon was first spotted in the early 1980s by NASA's Voyager spacecraft, but its full shape wasn't formally confirmed until 1988 after analysing flyby data. It was later studied in breathtaking detail by the Cassini probe, which orbited Saturn from 2004 to 2017. The southern decagon is a much more recent discovery. Because of Saturn's axial tilt, its south pole was hidden from Earth's view from 2012 until 2023. As it came back into view, Hubble images from 2023 onwards revealed the emerging 10-sided pattern for the first time. Its formation after the Cassini mission ended highlights how dynamic and changeable the outer planets can be.
The North Pole's Hexagon Changes Colour
One of the most fascinating discoveries from the Cassini mission was that the northern hexagon changes colour with the seasons. A Saturnian year lasts about 29 Earth years, meaning its seasons are incredibly long. During its northern winter, the hexagon appeared to have a bluish hue. As spring arrived and sunlight returned to the pole, it began to transform into a golden, hazy yellow. Scientists believe this is due to photochemical reactions in the atmosphere. Increased sunlight breaks down methane, creating hydrocarbon particles that form a kind of smog, similar to what happens on Earth. This seasonal colour shift is a stunning reminder that Saturn is not a static ball of gas but a living, breathing world with complex weather.
