Hubble spots a massive ten-sided atmospheric wave tightening around Saturn’s south pole as it spins and strengthens and scientists have never seen anything like it before

Saturn has long kept one geometric secret at its north pole — a colossal six-sided storm that has puzzled scientists for decades. Now, Hubble has caught the planet conjuring something new at the opposite end: a vast, ten-sided atmospheric wave wrapping around its south pole, a structure no telescope or spacecraft had ever recorded there before.

What makes it stranger still is the timing. Cassini orbited Saturn for thirteen years and saw nothing like it. Hubble has been watching since 1990. Yet this decagon appears to have formed only recently — and it’s still strengthening.

A ten-sided giant hiding in plain sight

The decagon is exactly what it sounds like: a massive, ten-sided atmospheric wave looping around Saturn’s south pole. Hubble confirmed it, and the data traced its emergence back to 2023. This marks the first time scientists have detected a large, regular-sided jet pattern in Saturn’s southern hemisphere — a region they’ve been watching carefully for decades without ever seeing anything like it.

The first hints didn’t come from space at all. In 2024, ground-based observers noticed a subtle undulating band near the southern pole, and additional ground imagery in 2025 strengthened the case. Only then did Hubble step in to confirm what the images were suggesting — and to push the timeline of the structure’s formation back another year.

How Hubble — and amateur eyes — cracked the case

The discovery began with a network of patient observers. The University of the Basque Country manages a platform called the Planetary Virtual Observatory Laboratory, collecting ground-based planetary images contributed by astronomers around the world. It was inside that archive that lead author Agustín Sánchez-Lavega, along with amateur astronomers Trevor Barry and Jean-Paul Oger, first spotted the faint, rippling band near Saturn’s southern pole.

Amateur observers catching something this significant isn’t a fluke — it’s the model working as intended. Wide participation creates more eyes, more images, and more chances to notice something unusual before it disappears or changes shape entirely.

Ground-based images have real limits, though. Earth’s atmosphere blurs and distorts incoming light, making fine detail hard to resolve at planetary distances. Hubble, operating above that interference, provided the sharp, high-resolution views needed to confirm the wave’s ten-sided geometry across full rotations of the planet. It also observed Saturn across different wavelengths of light — and because each wavelength probes a different altitude in Saturn’s atmosphere, that approach revealed the decagon extending vertically through multiple atmospheric levels, making it a genuinely deep structure rather than a thin surface feature.

Similar to the northern hexagon — but not quite

Saturn’s northern hexagon is one of the most recognizable features in the solar system: a six-sided atmospheric wave that has persisted, largely unchanged, for more than 40 years. Scientists have studied it extensively, and it has become a benchmark for understanding how jet streams on giant planets can lock into stable geometric shapes.

The decagon invites an obvious comparison — but the differences matter as much as the similarities. The southern structure has ten sides instead of six, and it appears to be newly forming and actively strengthening, rather than sitting in a long-term stable state. “The northern hexagon has been there every time we’ve looked for more than 40 years,” said Amy Simon, OPAL principal investigator at NASA’s Goddard Space Flight Center. “This feature is different — it appears to be strengthening.”

What makes the decagon’s sudden appearance especially puzzling is what came before it: nothing. NASA‘s Cassini spacecraft orbited Saturn from 2004 to 2017 and recorded no sign of a lasting southern formation. Hubble has been searching for a southern counterpart to the hexagon since 1990. Sánchez-Lavega noted that Cassini “showed no inkling of a long-lived formation.” The decagon seems to have materialized only recently, with no apparent precursor.

A structure rooted deep in Saturn’s atmosphere

The decagon sits within one of Saturn’s powerful jet streams. Its reach across multiple atmospheric layers confirms it isn’t simply a cloud pattern drifting at one altitude — it’s a vertically extended structure, shaped by dynamics that run deep into the planet’s atmosphere.

Tracking something like this requires patience. Hubble’s OPAL program — Outer Planet Atmospheres Legacy — has photographed the outer planets annually for more than a decade, and that sustained record is what allows scientists to distinguish a genuinely new feature from a temporary fluctuation.

“A lot of the discoveries we see coming from OPAL are not just based on one observation, but on years and years of data,” said Mike Wong, a study co-author at the University of California, Berkeley. “Regular observations over time are enabling a lot of new findings.” The observational window was also shaped by Saturn’s seasons — as the planet’s south pole gradually tilted back into view from Earth, it created the conditions that made this discovery possible.

What scientists hope to learn next

The most pressing questions don’t yet have answers. Why did the decagon form now, after decades of nothing? How long will it last — will it stabilize into something as enduring as the northern hexagon, or keep shifting?

Simon described the situation plainly: scientists have “the rare opportunity to watch a giant atmospheric pattern develop.” That opportunity won’t last indefinitely, making continued observation urgent. The team plans to combine future Hubble data with observations from NASA’s James Webb Space Telescope and run the results through computer models to probe the wave’s origin and internal dynamics. Webb’s infrared sensitivity could reveal details about temperature and composition that visible-light observations can’t capture alone.

The broader implications reach beyond Saturn. Understanding how jet streams on giant planets lock into geometric shapes — and why those shapes sometimes change — could shed light on atmospheric dynamics across the outer solar system, and possibly draw unexpected connections to circulation patterns here on Earth. Scientists are watching closely, knowing they may be witnessing the early life of something that could persist for generations.