Ten-sided wave undulates around Saturn’s south pole

Why in the News

Scientists have found a decagonal wave, a standing pattern with ten sides, around Saturn’s south pole. It is the first time such a feature has been reported at that pole. The finding rests on images taken from space and ground telescopes between 2023 and 2025. Saturn’s north pole has been known for decades to carry a long-lasting hexagonal wave, so the planet now presents two polar polygons with different numbers of sides. The question that follows is why one atmosphere produces two different wave patterns at its two poles.

What has been observed at Saturn’s south pole?

1. The shape: A wave with ten sides encircles the south pole, the counterpart of the six-sided pattern long known at the north.
2. The evidence base: It was identified from images taken by space and ground telescopes across 2023 to 2025, so it has been seen over a span of years rather than in a single observation.
3. The motion: The whole pattern drifts slowly eastward around the pole.
4. The oscillation: The decagon’s vertices, the ten corners where the sides meet, move back and forth on a cycle of 32 days.

What do researchers think the feature is?

1. It has depth, not just outline: The wave is treated as a vertical structure extending into the atmosphere, not a pattern confined to the visible cloud tops.
2. The first candidate cause: Unstable winds are one proposed origin, meaning a fast circumpolar flow that breaks into a regular wave pattern rather than running smooth.
3. The second candidate cause: A nearby anticyclone, a high-pressure rotating storm system, is the other proposed origin, forcing the wave from outside.

How does this compare with the north-polar hexagon?

1. The hexagon is old and stable: It was first seen in Voyager images in the early 1980s and observed again from Saturn orbit two decades later, so it has persisted across most of a Saturnian year.
2. It is very large: The hexagon spans of the order of 30,000 km, wider than the Earth, and is understood as the path of a fast jet stream circling the pole.
3. The wave number is what differs: A six-sided and a ten-sided pattern imply different jet speeds and different shear across the jet, so the two poles are not mirror images of each other.
4. The south pole already carried a distinct feature: A hurricane-like polar vortex with a well-defined eyewall was imaged there in the previous decade, which is a different phenomenon from a polygonal jet.

Why is Saturn’s south pole harder to study?

1. No spacecraft is there now: The only orbiter to have studied Saturn from close range ended its mission in 2017, so all current work depends on remote imaging from Earth orbit and from the ground.
2. Season controls the view: Saturn is tilted about 27 degrees and takes roughly 29 Earth years to orbit the Sun, so each pole is favourably lit only for part of that cycle, and the planet passed its most recent equinox in 2025.
3. Resolution is the limiting factor: Telescopes hundreds of millions of kilometres away resolve polar detail far less finely than an orbiting camera, which is why a repeated pattern is easier to detect than its internal structure.

Conclusion

Two polar polygons with different side counts on the same planet is a constraint on any model of Saturn’s atmospheric circulation, because a single explanation now has to produce both. Whether the southern feature holds for decades as the northern one has, or decays within a few years, is the question the next stretch of telescope observation will settle. No dedicated mission to Saturn’s atmosphere is scheduled, so that answer will come from the ground and from Earth-orbiting instruments rather than from a return visit.

Back2Basics: Cassini-Huygens

1. It was a joint mission of the National Aeronautics and Space Administration, the European Space Agency and the Italian Space Agency to study Saturn, its rings and its moons.
2. It was launched in 1997 and entered orbit around Saturn in 2004, becoming the first spacecraft to orbit the planet.
3. It carried the Huygens probe, which landed on Titan in 2005, the first landing in the outer solar system.
4. The mission ended in September 2017 with a deliberate plunge into Saturn’s atmosphere, chosen to avoid contaminating potentially habitable moons.

Matching Previous Year Question

“Which one of the following planets has largest number of natural satellites or moons ? (a) Jupiter (b) Mars (c) Saturn (d) Venus”