NASA’s Hubble Space Telescope has spotted a ten-sided wave at Saturn’s south pole. The shape is called a decagon. It is the first large regular-sided pattern ever seen in the planet’s southern hemisphere. The discovery was made by the Hubble OPAL programme. The wave is made of about 10 segments, each nearly 17,000 kilometres long. A team led by Agustin Sanchez-Lavega of the University of the Basque Country published the finding in Science Advances. The researchers say the decagon appears to be strengthening over time. Saturn’s north pole has a famous six-sided hexagon. That feature has been watched for over 40 years. Scientists say seasonal changes on Saturn drive these giant jet streams. The finding helps explain how giant planets’ atmospheres work. Saturn’s northern hexagon has been watched for over 40 years. Scientists say seasonal change drives these giant jet streams. The finding helps explain how giant planet atmospheres work. More Hubble observations are planned.