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Bizarre Hexagon On Saturn May Be 180 Miles Tall (space.com)
Iwastheone shares a report from Space.com: The weird hexagon swirling around Saturn's north pole is much taller than scientists had thought, a new study suggests. Researchers have generally regarded the 20,000-mile-wide (32,000 kilometers) hexagon -- a jet stream composed of air moving at about 200 mph (320 km/h) -- as a lower-atmosphere phenomenon, restricted to the clouds of Saturn's troposphere. But the bizarre structure actually extends about 180 miles (300 km) above those cloud tops, up into the stratosphere, at least during the northern spring and summer, a new study suggests. The hexagon, which surrounds a smaller circular vortex situated at the north pole, has existed for at least 38 years; NASA's Voyager 1 and Voyager 2 spacecraft spotted the sharp-cornered feature when they flew by Saturn in 1980 and 1981, respectively. Scientists started to get much more detailed looks at the hexagon in 2004, when NASA's Cassini spacecraft began orbiting the ringed planet. But Cassini's hexagon observations were pretty much confined to the troposphere for a decade after its arrival; springtime didn't come to Saturn's north until 2009, and low temperatures in the stratosphere continued to compromise measurements by the probe's Composite Infrared Spectrometer (CIRS) instrument for another five years.
The formation of a stratospheric hexagon appears to be tied to the warming brought on by the change of seasons, the research team wrote in the new study. Indeed, Cassini spied a vortex high above the south pole during its early years at Saturn, when that hemisphere was enjoying summer. (Saturn takes 30 Earth years to orbit the sun, so seasons on the ringed planet last about 7.5 years apiece.) But the southern stratospheric vortex wasn't hexagonal. And neither, for that matter, is the vortex that spins around the south pole lower down, in the tropospheric clouds, the researchers said. "This could mean that there's a fundamental asymmetry between Saturn's poles that we're yet to understand, or it could mean that the north polar vortex was still developing in our last observations and kept doing so after Cassini's demise," study lead author Leigh Fletcher, of the University of Leicester in England, said in a statement.
The formation of a stratospheric hexagon appears to be tied to the warming brought on by the change of seasons, the research team wrote in the new study. Indeed, Cassini spied a vortex high above the south pole during its early years at Saturn, when that hemisphere was enjoying summer. (Saturn takes 30 Earth years to orbit the sun, so seasons on the ringed planet last about 7.5 years apiece.) But the southern stratospheric vortex wasn't hexagonal. And neither, for that matter, is the vortex that spins around the south pole lower down, in the tropospheric clouds, the researchers said. "This could mean that there's a fundamental asymmetry between Saturn's poles that we're yet to understand, or it could mean that the north polar vortex was still developing in our last observations and kept doing so after Cassini's demise," study lead author Leigh Fletcher, of the University of Leicester in England, said in a statement.
I saw a pot at a musuem filled with water and glitter. It was hooked up to a motor which would swirl the glitter water. At just the right amount of swirl, the pattern formed inside was hexagonal. Fluid dynamics, all natural, no aliens involved.
Oh, and for all you foreigners on Slashdot: the US does not use "imperial" measurements. Only the countries that gained their independence from the UK in the 20th Century used those (Australia, Canada, New Zealand, etc.), as well as the UK, obviously. The US uses "Customary" units which evolved from imperial units but had most of the weirdness removed (rationalized).
The origin of the hexagon is no real mystery. It was recreated in a laboratory tank 8 years ago. (Link includes a video showing a hexagon forming in the tank). It forms when the spin rates between the inner and outer fluid hit a certain ratio. Normally the speed differential creates a chaotic interface at the boundary layer. But at certain ratios it creates a standing wave which forms a hexagon (well, not really standing since it moves, but in a certain rotational frame it's a standing wave).
It's impressive that the hexagon is that tall, since that implies the wind speeds are consistent through that height.