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Sitting atop Saturn's north pole is one of the Solar System's most striking weather patterns: a rotating, color-changing hexagon slightly wider than Earth. A new study shows there's another hexagon directly on top of the first one-and that's weird.
Saturn's hexagon has visited the planet, including Voyager, Hubble, and Cassini, though its structure is something of a mystery. In 2016, astronomers noticed that the hexagon had changed in hue, from blue to gold. New observations continue to show that there's a lot that scientists do not know about Saturn and its hexagon.
"We're seeing it goes straight into the stratosphere a long, long way. That's unexpected, "Glenn Orton, one of the study's authors and a physicist at NASA's Jet Propulsion Laboratory, told Gizmodo. "I'm supposed to be wise about the dynamics, but I'm at a loss.
The scientists set out to study the North Polar Stratospheric Vortex (NPSV). This is a swirling feature that forms during Saturn's spring and summer in the stratosphere, the layer above the cloud tops, and disappears during the winter. The NPSV includes warmer temperatures and the increased presence of hydrocarbons, molecules made from hydrogen and carbon like methane. Cassini's Composite Infrared Spectrometer Demonstrated "a significant surprise," according to the paper published this week in Nature Communications.
The NPSV had a hexagonal-shaped boundary that looked exactly like the well-known persistent hexagon in the lowest level of Saturn's atmosphere. Somehow, during Saturn's equivalent of spring and summer, the process that creates its hexagon appears to influence 300 kilometers (180 miles) upward.
Scientists think that the well-known hexagon structure comes from Rossby waves, larger-scale movements of the entire structure of the planet's gas, rather than the motion of the gas molecules themselves, like earth's jet stream meandering, caused by the planet's rotation.
As it is known, higher-up hexagon forms, or it is formed separately from the lower hexagon, or somehow there is interaction between two layers of Saturn's atmosphere that produces an enormous single hexagon structure. The two layers can not communicate, and the observations show aligned hexagons. Perhaps the Rossby waves are just strong enough to leave an imprint on the stratosphere.
There's a lot to learn about the vortex. The Composite Infrared Spectrometer on board Saturn year lasts 30 Earth years. Observations began in 2013 and ended in 2017. The vortex will continue to evolve until the planet's fall equinox in 2024, according to a press release from the European Space Agency.
Astronomers have known about Saturn's hexagon for a shorter period of time, say, Jupiter's Great Red Spot. "It's possible we've seen it long enough to see change," Orton said, "So we're gonna just keep looking."
[Nature Communications]Source link
