CAPE CANAVERAL, Fla. — Scientists have discovered an enormous 10-sided wave pattern in the icy ammonia clouds over Saturn's south pole.
The spinning, meandering decagon appears to be even bigger and more unstable than the hexagon of clouds around Saturn's north pole that was spied by NASA's twin Voyagers in the 1980s, the Spanish-led team reported Wednesday.
This new jet stream formation popped up in the Hubble Space Telescope's sights in 2023 after earlier observations came up empty. The researchers suspect the bizarre atmospheric phenomenon may have formed between 2017 and 2023, when Saturn's south pole was tilted away from Earth and therefore out of view.
It could still be evolving, with a single side of the decagon already exceeding 10,000 miles (16,700 kilometers).
The findings are significant because it shows “the ‘unique’ hexagon is not as extraordinary as we thought," lead author Agustin Sanchez-Lavega with the University of the Basque Country said in an email.
The findings were published in the journal Science Advances.
Although all of the solar system’s planets with atmospheres have wave-spawning disturbances, only Saturn churns them out looking like polygons, geometric shapes bounded by straight lines.
Both sit on jet streams, but the hexagon is practically stationary whereas the decagon migrates eastward at a tame 6 mph (10 kph).
“Saturn still has the ability to surprise us," the University of Leicester's Leigh Fletcher said in a statement. He measured the wind in the decagon as part of the study using the European Southern Observatory's Very Large Telescope in Chile.
By comparing these two formations on opposite ends of Saturn, scientists can learn more about the weather patterns of giant gas planets, according to Sanchez-Lavega.
“This is a highly interesting phenomenon that appears to be unique to Saturn, and we want to know why,” he said.
Sanchez-Lavega wonders whether they might be related to the cyclones on Jupiter that are arranged in polygonal shapes. Improving views of Saturn's southern hemisphere over the next several years should allow astronomers to capture more details of the decagon and perhaps solve “this intriguing atmospheric mystery,” he said.
It’s unclear whether the decagon will last as long as the hexagon, which has been visible by spacecraft for more than 40 years. That is longer than a Saturnian year, which is equivalent to 30 Earth years.
“For the time being, all I can confirm is that the decagon is still there,” Sanchez-Lavega said.
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