Astronomers Discover New Atmospheric Structure on Saturn
A team of astronomers has identified a striking decagonal atmospheric feature near Saturn’s south pole. This discovery introduces a significant new polygonal structure on the gas giant, complementing its well-known hexagonal formation situated at the north pole, which has been observed for over 44 years. The confirmation of the decagon was made possible through images captured by the Hubble Space Telescope, and the findings have been published in the journal Science Advances.
It is important to clarify that the formations at both the north and south poles are not solid structures, akin to a wall or rock formation. Rather, they represent intricate patterns created by clouds as a result of atmospheric dynamics. Unlike Earth, Saturn lacks a defined solid surface. If one were to descend through the planet’s atmosphere, they would experience gradually increasing pressure and density, but would never reach a “ground” on which to land.
Each side of the newly discovered decagon measures approximately 16,800 kilometres, exceeding Earth’s diameter of about 12,700 kilometres. This geometric figure is associated with a jet stream that reaches speeds of 116 metres per second, or around 418 kilometres per hour. For context, on our planet, a category 5 hurricane, which is classified as extremely intense, begins at sustained winds of around 252 km/h. Interestingly, despite the jet stream’s remarkable velocity, the decagonal pattern itself moves around Saturn at a mere 2.5 metres per second, equivalent to approximately 9 km/h.
The Quest for a Southern Counterpart
The formation on this ringed planet appears to have emerged recently. For decades, scientists have sought a potential counterpart to the famous northern hexagon. If Saturn hosts such a large polygonal feature in one hemisphere, could a similar structure exist in the other? However, previous missions observing the planet did not uncover a corresponding stable structure in the southern hemisphere. The search was further complicated by the tilt of Saturn, which rendered its southern hemisphere unfavourably visible from Earth for extended periods.
The first clues emerged from terrestrial observations collected through planetary astronomy networks, which included contributions from amateur astronomers. As more images were gathered, it became increasingly apparent that something unusual was occurring in Saturn’s southern cloud bands. Hubble’s data allowed researchers to trace the pattern back to images taken in 2023. Continued monitoring revealed that by 2025, the ten vertices of the decagon were much more clearly developed, confirming the presence of a new polygonal feature in the planet’s atmosphere.
Exploring the Origins of Atmospheric Structures
Since the discovery of the hexagon at the north pole, scientists have proposed various hypotheses to explain the origins of these atmospheric structures. One of the leading physical explanations suggests that the polygons are visible manifestations of enormous atmospheric waves confined by powerful jet streams.
To illustrate this concept simplistically, consider the analogy of ocean waves. A wave is not an object moving through the ocean; rather, it is a disturbance that propagates through the water. Its behaviour varies depending on the environment in which it travels and the boundaries it encounters. On Saturn, the medium is the atmosphere, the waves are large atmospheric disturbances, and the jet streams that confine them act like the edges of a beach or bay—albeit, in this case, the “beach” encircles the entire planet.
When factors such as Saturn’s rapid rotation, wind speeds, and variations in these jet streams converge, the waves can become confined and organised into regular patterns. A current that undulates six times around the planet may form a hexagon, while one that does so ten times may create a decagon. This is how an atmosphere, devoid of solid structures, can ultimately produce patterns that appear as gigantic polygons from above.
Unanswered Questions and Future Research
Despite this progress, numerous questions remain unanswered. For instance, the depth to which these geometric figures extend is still unknown, as is the longevity of the new decagon, whether its formation is linked to Saturn’s seasons, and what specifically triggers its development. While science can elucidate how an atmosphere generates these patterns, it has yet to determine what initiates the process in each instance.
Researchers aim to gain further insights by monitoring the evolution of the decagon. To this end, they plan to continue observations with the Hubble Space Telescope and the James Webb Space Telescope, employing more advanced atmospheric models to reconstruct the conditions that led to the formation of this intriguing structure.