Pasadena, Calif. -- An odd, six-sided, honeycomb-shaped feature circling the entire north pole of Saturn has captured the interest of scientists with NASA's Cassini mission.

NASA's Voyager 1 and 2 spacecraft imaged the feature over two decades ago. The fact that it has appeared in Cassini images indicates that it is a long-lived feature. A second hexagon, significantly darker than the brighter historical feature, is also visible in the Cassini pictures. The spacecraft's visual and infrared mapping spectrometer is the first instrument to capture the entire hexagon feature in one image.

"This is a very strange feature, lying in a precise geometric fashion with six nearly equally straight sides," said Kevin Baines, atmospheric expert and member of Cassini's visual and infrared mapping spectrometer team at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We've never seen anything like this on any other planet. Indeed, Saturn's thick atmosphere where circularly-shaped waves and convective cells dominate is perhaps the last place you'd expect to see such a six-sided geometric figure, yet there it is."



The hexagon is similar to Earth's polar vortex, which has winds blowing in a circular pattern around the polar region. On Saturn, the vortex has a hexagonal rather than circular shape. The hexagon is nearly 25,000 kilometers (15,000 miles) across. Nearly four Earths could fit inside it.

The new images taken in thermal-infrared light show the hexagon extends much deeper down into the atmosphere than previously expected, some 100 kilometers (60 miles) below the cloud tops. A system of clouds lies within the hexagon. The clouds appear to be whipping around the hexagon like cars on a racetrack.

"It's amazing to see such striking differences on opposite ends of Saturn's poles," said Bob Brown, team leader of the Cassini visual and infrared mapping spectrometer, University of Arizona, Tucson. "At the south pole we have what appears to be a hurricane with a giant eye, and at the north pole of Saturn we have this geometric feature, which is completely different."

The Saturn north pole hexagon has not been visible to Cassini's visual cameras, because it's winter in that area, so the hexagon is under the cover of the long polar night, which lasts about 15 years. The infrared mapping spectrometer can image Saturn in both daytime and nighttime conditions and see deep inside. It imaged the feature with thermal wavelengths near 5 microns (seven times the wavelength visible to the human eye) during a 12-day period beginning on Oct. 30, 2006. As winter wanes over the next two years, the feature may become visible to the visual cameras.

Based on the new images and more information on the depth of the feature, scientists think it is not linked to Saturn's radio emissions or to auroral activity, as once contemplated, even though Saturn's northern aurora lies nearly overhead.

The hexagon appears to have remained fixed with Saturn's rotation rate and axis since first glimpsed by Voyager 26 years ago. The actual rotation rate of Saturn is still uncertain.

"Once we understand its dynamical nature, this long-lived, deep-seated polar hexagon may give us a clue to the true rotation rate of the deep atmosphere and perhaps the interior," added Baines.

The hexagon images and movie, including the north polar auroras are available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov and http://wwwvims.lpl.arizona.edu .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Visual and Infrared Mapping Spectrometer team is based at the University of Arizona.

I have to admit, a precise hexagon seems like one rather freaky coincidence. Things that kind of look like a face if you look at them in the right light, from the right angle...well, we see that kind of crap here on earth all the time, with "Jesus on my toast!" stories. But this? How the hell does a hexagonal weather pattern (if that is what they're suggesting it to be) form? Oo;

I have no idea, but I can't wait to find out! This has got to be one of the weirdest natural features we've ever found.

A sequence of map-projected Voyager 2 images of Saturn is used to show that a hexagonally-shaped cloud feature surrounds that planet's north polar region; this hexagonal pattern appears to be stationary despite the 100 m/sec flow velocity for individual cloud features. This rotation rate, which is consistent with the radio rotation period, suggests either the interaction of the feature with observed radio emissions or the existence of a cause common to both, such as a feature of the deep planetary flow.

How does that explain the polygonal shape though?

Geometric whirlpools revealed
Recipe for making symmetrical holes in water is easy.
Philip Ball

Bizarre geometric shapes that appear at the centre of swirling vortices in planetary atmospheres might be explained by a simple experiment with a bucket of water.

Researchers at the Technical University of Denmark in Lyngby have created similar geometric shapes (holes in the form of stars, squares, pentagons and hexagons) in whirlpools of water in a cylindrical bucket1. The shapes appear easily enough once the bucket is spinning at a rate of one to seven revolutions per second, they say.

Tomas Bohr and colleagues made plexiglass buckets, 13 and 20 centimetres across, with metal bottoms that could be rotated at high speed by a motor. They filled the bucket with water and spun the bottom to whip up the liquid into a whirlpool that rose up the sides of the container.

This set-up is very similar to the rotating bucket that Isaac Newton used in the seventeenth century to investigate centrifugal forces.

The researchers found that once the plate was spinning so fast that the water span out to the sides, creating a hole of air in the middle, the dry patch wasn't circular as might be expected. Instead it evolved, as the bucket's spin sped up, from an ellipse to a three-sided star, to a square, a pentagon, and, at the highest speeds investigated, a hexagon.

In a spin

The apparatus needed to see this strange effect is so simple that it seems surprising that it has never been reported before. Bohr suggests that either no one was looking for it, or they simply didn't spin water fast enough.

Harry Swinney, a specialist in pattern-forming fluid flows at the University of Texas at Austin, says the new observation is roughly in line with what one might expect. At high enough rotation speeds, he says, a fluid will always experience some flow instability that creates a symmetrical structure.

Similar polygonal shapes have been reported in gigantic, vortex-like flows in the atmosphere of our planet and others, as well as in the eye of a hurricane. And an immense, hexagonal-shaped vortex was spotted by the Voyager spacecraft at the northern pole of the gas-giant planet Saturn.

These natural structures have never been fully explained. Could they be produced by the effect observed by the Danish team? "I expect that similar conditions might apply in these atmospheric flows," says Bohr. But he admits that at this stage he doesn't understand the pattern-forming process well enough to be sure of the comparison.

Swinney, meanwhile, thinks that the process is unlikely to apply to large-scale flows such as that on Saturn, but might be relevant to smaller-scale phenomena such as tornadoes.

That's another instance of a similar phenomenon. Apparently they have no idea why it is the way it is.

Fucking trippy...

Just because it's a hexagon doesn't make it that odd. Snowflakes are on the whole naturally hexagonal fractal thingies. At least, stereotypically in artists' depictions. Where I am right now and have lived for the past 5 years it snows every couple hundred years so I've never seen one in a half decade. Both are normal atmospheric phenomina. As far as movement one could call the moon's revolution and orbit equalling eachother just as odd as a stationary cloud formation, but maybe it is a possibility it's just so big any minor movement doesn't matter, like the Big Red Spot of Jupiter?

Here's one explanation.

No, no, this is clearly the Warpspace phenomen detected a few years back with this sound. It's the reason the Grey Knights are stationed on Titan afterall.

No, no, this is clearly the Warpspace phenomen detected a few years back with this sound. It's the reason the Grey Knights are stationed on Titan afterall.