Hubble confirms a new decagon-shaped wave circling Saturn's south pole
NASA's Hubble Space Telescope has confirmed a huge, evolving ten-sided atmospheric wave circling Saturn's south pole, the planet's first known southern counterpart to its famous northern hexagon. The decagon only appeared in observations starting in 2023 and was fully formed by 2025, something NASA's Cassini spacecraft never detected in its thirteen years orbiting Saturn. The peer-reviewed finding was published in the journal Science Advances.
For nearly fifty years, Saturn's north pole has been defined by a six-sided jet stream known as the hexagon, first spotted by NASA's Voyager spacecraft in the 1980s. Astronomers had long wondered whether the southern hemisphere hid a mirror image. NASA's Hubble Space Telescope has now confirmed it does: a huge, evolving ten-sided wave, a decagon, circling Saturn's south pole. The finding, led by Agustin Sanchez-Lavega of the University of the Basque Country with NASA's Amy Simon and UC Berkeley's Michael Wong, is published in the peer-reviewed journal Science Advances. Saturn's south pole dropped out of view from Earth in 2012 due to the planet's axial tilt and only became visible again in 2023, when ground-based images showed a faint ten-vertex shape near 63 degrees south. By 2024 the shape had sharpened, and by 2025 all ten vertices stood fully formed. NASA's Cassini spacecraft, which orbited Saturn for thirteen years until 2017, recorded no sign of a long-lived formation there. Simon says the pattern extends through multiple layers of the atmosphere, not just the cloud tops, and researchers still don't know what triggered it or whether it will hold the way the northern hexagon has for over forty years. Further observations from Hubble and the James Webb Space Telescope, plus computer modelling, are planned to determine how it formed and how long it may last.