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The hexagonal storm at Saturn’s north pole has been known for decades but is far from explained. Now, a counterpart has surprisingly formed at the south pole.
The composite image on the right, created from multiple exposures, shows the decagon
(Image: NASA, ESA, STScI, Agustin Sánchez-Lavega (UPV), Amy Simon (NASA-GSFC), Michael Wong (UC Berkeley); Image Processing: Alyssa Pagan)
An unexpected ten-sided storm has formed over Saturn’s south pole; the decagon is clearly recognizable in new images from the Hubble Space Telescope. The first indications of the structure were discovered by a research team led by Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain, in an amateur astronomical image. However, Hubble provided the final confirmation and the best images. The discovery was made just over 40 years after the famous hexagon was found at Saturn’s north pole. How the two form, why they create an angular structure, and why they differ so distinctly is unclear, explains the research group.
The ten-sided storm is an atmospheric wave that encircles the ringed planet’s south pole, explains NASA. It is located within the powerful jet stream and extends across various regions of the atmosphere, so it is likely not a simple cloud formation. What is particularly interesting to the researchers is that the structure formed only relatively recently. "The question is, why did it suddenly form now when we haven’t seen one before?" says NASA researcher Amy Simon. The hexagon at the north pole has been there for decades whenever it was looked for, while the decagon only began forming in 2023.
With a filter, the corners become particularly visible (the "X" marks areas for which no data is available)
(Image: NASA, ESA, STScI, Agustin Sánchez-Lavega (UPV), Amy Simon (NASA-GSFC), Michael Wong (UC Berkeley); Image Processing: Alyssa Pagan)
A phenomenon like the polygonal storms on Saturn is not found anywhere else in the solar system, even though the jagged structure is not quite as unique as it appears. A depiction of the jet streams on Earth shows a similar pattern. However, on our home planet, the phenomenon is not nearly as stable, primarily due to surface obstacles. On the gas giant Saturn, on the other hand, there are no such obstacles, which is likely why at least the hexagon at the north pole can persist for decades or even centuries. This leaves the question of why the decagon at the south pole is apparently not as long-lived. The research group intends to continue observing the storm to find out if it stabilizes and how it originated.
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The discovery was made possible thanks to a program at the University of Bilbao called Planetary Virtual Observatory and Laboratory. Under this program, astronomers who do not pursue astronomy professionally can submit astronomical images. Based on images submitted through this program, Sánchez-Lavega, along with two amateur astronomers, discovered "a subtle undulating band along the southern pole," NASA explains. A year later, it was more clearly visible. However, only Hubble could fully image the structure because it can capture an entire rotation of the ringed planet from Earth orbit. The discovery is presented in a scientific article in the research journal Science Advances.
(mho)
