How did Saturn grow a 10-sided polar wave?
Astronomers reported in early September that a newly emerged decagon now encircles Saturn’s south pole.
Hubble observations dating to 2023 show a giant, evolving 10-sided wave near Saturn’s south pole, the first large regular-sided jet pattern observed in the planet’s southern hemisphere.[1][6] Ground-based observers detected an undulating band in 2024, while polar projections of Hubble images from 2…
Hubble observations dating to 2023 show a giant, evolving 10-sided wave near Saturn’s south pole, the first large regular-sided jet pattern observed in the planet’s southern hemisphere.[1][6] Ground-based observers detected an undulating band in 2024, while polar projections of Hubble images from 2024 and 2025 clearly revealed the decagon near 63°S.[1][6]
Why it matters: Unlike Saturn’s northern hexagon, which has persisted through more than 40 years of observations, the southern decagon appears to have formed recently and is still strengthening, giving researchers a rare opportunity to watch a planet-scale atmospheric pattern develop.[6]
Key insights: Different Hubble filters show that the decagon extends through multiple atmospheric layers rather than existing only at cloud level.[1][6] | Its visible upper-tropospheric winds move at roughly 400 kilometers per hour.[1] | A nearby anticyclone first observed in 2023 darkened sharply in 2025 before the decagon emerged, making it a possible source of the initial disturbance.[1] | Researchers still do not know which aerosols produce the wave’s blue color or how its structure continues deeper into Saturn’s atmosphere.[1]
Cheatsheet facts: What changed: A 10-sided atmospheric wave became clearly visible around Saturn’s south pole after subtle signs appeared in observations dating to 2023.[1][6] | Why now: Saturn’s seasons brought the south pole back into Earth’s view, while annual OPAL imaging and ground-based observations supplied the multi-year record needed to identify the developing structure.[1][6] | Watch next: Continued Hubble and James Webb Space Telescope observations will test whether the decagon stabilizes like the northern hexagon, while computer models examine how it formed.[6]
Hubble observations dating to 2023 show a giant, evolving 10-sided wave near Saturn’s south pole, the first large regular-sided jet pattern observed in the planet’s southern hemisphere.[1][6] Ground-based observers detected an undulating band in 2024, while polar projections of Hubble images from 2024 and 2025 clearly revealed the decagon near 63°S.[1][6]
Why it matters: Unlike Saturn’s northern hexagon, which has persisted through more than 40 years of observations, the southern decagon appears to have formed recently and is still strengthening, giving researchers a rare opportunity to watch a planet-scale atmospheric pattern develop.[6]
Key insights: Different Hubble filters show that the decagon extends through multiple atmospheric layers rather than existing only at cloud level.[1][6] | Its visible upper-tropospheric winds move at roughly 400 kilometers per hour.[1] | A nearby anticyclone first observed in 2023 darkened sharply in 2025 before the decagon emerged, making it a possible source of the initial disturbance.[1] | Researchers still do not know which aerosols produce the wave’s blue color or how its structure continues deeper into Saturn’s atmosphere.[1]
Cheatsheet facts: What changed: A 10-sided atmospheric wave became clearly visible around Saturn’s south pole after subtle signs appeared in observations dating to 2023.[1][6] | Why now: Saturn’s seasons brought the south pole back into Earth’s view, while annual OPAL imaging and ground-based observations supplied the multi-year record needed to identify the developing structure.[1][6] | Watch next: Continued Hubble and James Webb Space Telescope observations will test whether the decagon stabilizes like the northern hexagon, while computer models examine how it formed.[6]