Saturn's Mysterious Hexagon Emerges from Winter Darkness

Dec 09, 2009
This movie from Cassini, made possible only as Saturn's north pole emerged from winter darkness, shows new details of a jet stream that follows a hexagon-shaped path and has long puzzled scientists.

(PhysOrg.com) -- After waiting years for the sun to illuminate Saturn's north pole again, cameras aboard NASA's Cassini spacecraft have captured the most detailed images yet of the intriguing hexagon shape crowning the planet.

The new images of the hexagon, whose shape is the path of a jet stream flowing around the north pole, reveal concentric circles, curlicues, walls and streamers not seen in previous images.

The last visible-light images of the entire hexagon were captured by NASA's Voyager spacecraft nearly 30 years ago, the last time spring began on Saturn. After the sunlight faded, darkness shrouded the north pole for 15 years. Much to the delight and bafflement of Cassini scientists, the location and shape of the hexagon in the latest images match up with what they saw in the Voyager pictures.

"The longevity of the hexagon makes this something special, given that weather on Earth lasts on the order of weeks," said Kunio Sayanagi, a Cassini imaging team associate at the California Institute of Technology. "It's a mystery on par with the strange that give rise to the long-lived Great of ."

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The hexagon was originally discovered in images taken by the Voyager spacecraft in the early 1980s. It encircles Saturn at about 77 degrees north latitude and has been estimated to have a diameter wider than two Earths. The jet stream is believed to whip along the hexagon at around 100 meters per second (220 miles per hour).

Early hexagon images from Voyager and ground-based telescopes suffered from poor viewing perspectives. Cassini, which has been orbiting Saturn since 2004, has a better angle for viewing the north pole. But the long darkness of Saturnian winter hid the hexagon from Cassini's visible-light cameras for years. Infrared instruments, however, were able to obtain images by using heat patterns. Those images showed the hexagon is nearly stationary and extends deep into the atmosphere. They also discovered a hotspot and cyclone in the same region.

The visible-light cameras of Cassini's imaging science subsystem, which have higher resolution than the infrared instruments and the Voyager cameras, got their long-awaited glimpse of the hexagon in January, as the planet approached equinox. Imaging team scientists calibrated and stitched together 55 images to create a mosaic and three-frame movie. The mosaics do not show the region directly around the because it had not yet fully emerged from winter night at that time.

Scientists are still trying to figure out what causes the hexagon, where it gets and expels its energy and how it has stayed so organized for so long. They plan to search the new images for clues, taking an especially close look at the newly identified waves that radiate from the corners of the hexagon -- where the jet takes its hardest turns -- and the multi-walled structure that extends to the top of Saturn's cloud layer in each of the hexagon's six sides. Scientists are also particularly intrigued by a large dark spot that appeared in a different position in a previous infrared image from . In the latest images, the spot appears in the 2 o'clock position.

Because does not have land masses or oceans on its surface to complicate weather the way Earth does, its conditions should give scientists a more elementary model to study the physics of circulation patterns and atmosphere, said Kevin Baines, an atmospheric scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who has studied the hexagon with Cassini's visual and infrared mapping spectrometer.

"Now that we can see undulations and circular features instead of blobs in the hexagon, we can start trying to solve some of the unanswered questions about one of the most bizarre things we've ever seen in the solar system," Baines said. "Solving these unanswered questions about the hexagon will help us answer basic questions about weather that we're still asking about our own planet."

Provided by JPL/NASA (news : web)

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User comments : 21

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Caliban
1.3 / 5 (4) Dec 09, 2009
Wonder how this atmospheric phenomenon may be influenced by the structure of the denser interior of the planet. Maybe a huge crystalline mass?
Husky
5 / 5 (2) Dec 09, 2009
that thought crossed my mind, a macroscopic shadow of a chrystal lattice. Another thought: one of a hexagons/honeycomb most interesting features is that it covers the most amount of surface with the least material, so maybe this is a state of equillibrium between gasses of differeent densities
SincerelyTwo
not rated yet Dec 09, 2009
Husky, that's badass, this phenomena came up once or twice before in the past couple years and for some reason never ran in to anything that explained it like that. I wonder how this could be modeled, it'd be a neat thing to try out. :]
Caliban
1 / 5 (2) Dec 09, 2009
It'll be fun to keep an eye out for developments on this- see how closely this idea may be borne out by the experts. It does seem reasonable- at least on the surface. Reminds me of rolling the larger snowballs to make a snowman from when I was a kid- I remember that when the snow was wetter, it frequently would compact into a hexagonal "ball", rather than the hoped-for sphere.
otto1923
not rated yet Dec 09, 2009
I wonder if it's in any way related to the hexagonal shape of lunar craters and the way they're formed-
Caliban
1 / 5 (2) Dec 09, 2009
@otto1923-
Wasn't aware of any hexagonal structure found in Lunar craters. Got any links? I saw a post from someone a day or two ago from a reader that had amassed a photo catalog of "square" impact craters in New Mexico, which were quite intriguing, but looked as if they might just as well have been reservoirs or pit mines or something. If they were, in fact, impact craters, they resembled something more like punctures made by some sort of four-sided object than some randomly-shaped object.
Hmmm...
Caliban
1 / 5 (3) Dec 09, 2009
Here's link for those square craters:

http://dl.dropbox...Craters.
MatthiasF
not rated yet Dec 09, 2009
@Husky: Not sure what you mean by "most amount of surface with the least material", but if you're referring to the ratio of surface area to volume, a dodecahedron that I assume you're describing does not have the highest ratio or the lowest. Tetrahedron wins the highest by a wide margin. If you meant the opposite, it would be a sphere.

http://en.wikiped...me_ratio

If we're talking only 2D shapes, I'm pretty sure a equilateral triangle or circle (respectively) would also win over a hexagon.
otto1923
not rated yet Dec 09, 2009
Read about hexagonal craters in an old moon book. Here's a link which confirms their existance:
http://adsabs.har...36..410V
-google lists discussions of mars, mercury, Mimas and elsewhere-
Caliban
1 / 5 (2) Dec 09, 2009
Thanks, otto
I'm surprised that I missed(or possibly forgot) this. Makes sense in terms of the characteristics of basaltic rocks.
Vlasev
not rated yet Dec 10, 2009
I was not able to find any resources, but I'm pretty sure I came across a column on making water vortexes with unusual shape of the vortex' "water ridge". If I recall correctly this was study made from German scientist couple of years ago.
Sepp
4.5 / 5 (2) Dec 10, 2009
Vlasev is right - here is a reference to the research showing that at the right frequency, vortices do resolve into stable geometric patterns.

http://mediarelat...earo.php
la7dfa
not rated yet Dec 10, 2009
If my memory serves me right we have similar patterns on Earths South pole from time to time.
You also get the same pattern if you put ice in the middle of a sheet of metal and heat the edges while swirling the sheet around.
SincerelyTwo
5 / 5 (1) Dec 10, 2009
la7dfa,

Actually, a really good example of this on earth, for which there's videos on youtube, is the eye of hurricanes. There's a good handful of media depicting their hexagon/pentagon shaped eyes. :D
RayCherry
not rated yet Dec 10, 2009
We saw similar patterns at the center of tropical hurricanes in the past few years, along with claims of 'manmade storms'.

It will be interesting to discover which wall of the hexagon is receiving the most external pressure and see how that is compensated for in the other walls, (imperfect geometry fluctuations), and also how the corners become more defined during peaks of external pressure one of more walls.

Further, does the shape rotate? Hurricane centers appear to rotate, but we don't understand the dynamics that cause it, or the circumstances that would cause the center to stop rotating - the shape on Saturn above a pole, it is not shifting across the surface of tropical ocean currents.

If the shape on Saturn is not altering its alignment at any time, what does it signify?
Jimster
not rated yet Dec 10, 2009
I do not understand what the big mystery is. A detailed consideration of Bernard Cells and/or Taylor Vortices will unravel the "astonishment". I am more astonished at NASA's amazement.
jimmy1010100
not rated yet Dec 10, 2009
mysticfree
Dec 10, 2009
This comment has been removed by a moderator.
MatthiasF
not rated yet Dec 10, 2009
Jimmy's second link seems like the most likely culprit. I'd be interested to see if the hexagon's nodes stayed in relatively the same locations depending on the sun's position. Could be interference from solar wind or other effects from the sun interrupting the vortex to create the shape.
Sanddog
Dec 10, 2009
This comment has been removed by a moderator.
jkju
1 / 5 (1) Dec 13, 2009
i just read that the cassini mission has a backdoor in hardware and software and this is the work of a group of hackers.
this would be the so called joke of the millenium
bluehigh
1 / 5 (1) Dec 13, 2009
What type of scientists are puzzled by this?
um are Geologists puzzled? or Chemists puzzled? or Physicists puzzled? or Biologists puzzled?

Do we have General Practioner type scientists that are qualified to be still figuring this out?

What type of scientist is an - imaging team associate?

antialias
not rated yet Dec 14, 2009
According to his bio Kunio Sayanagi is a postdoc in planetary sciences (which includes diciplines like planetary geology, geochemistry, geomorphology, planetary astrology, and geophysics).