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Spring Unveils Saturn's Hexagon
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Spring Unveils Saturn's Hexagon
PIA 11682

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Spring Unveils Saturn's Hexagon
PIA 11682

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  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.

The hexagon was hidden in darkness during the winter of Saturn's long year, a year that is equal to about 29 Earth years. But as the planet approached its August 2009 equinox and signaled the start of northern spring, the hexagon was revealed to Cassini's cameras. This is the first time the whole hexagonal shape has been mapped out in visible light by Cassini, and these images show unprecedented details of Saturn's high northern latitudes. The hexagon was originally discovered in images taken by Voyager spacecraft in the early 1980s. Since 2006, the Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument has been observing the hexagon at infrared wavelengths, but at lower spatial resolution than these visible light images.

Three large mosaics were used to create this three-frame movie. The mosaics used dozens of images and the constituent images were projected into polar projections to provide a complete view of the hexagon. The mosaics used in this movie do not show the region directly around the north pole because it had not yet fully emerged from the polar winter night. Seams between the images are visible in the third frame of the movie because the observation geometry in those images made removal of the seams difficult.

The six-sided shape remains a mystery. Scientists think the hexagon is a meandering jet stream at 77 degrees north latitude, but they don't know what controls the path the stream takes. These images also show new phenomena for scientists to decipher, such as waves that can now be seen radiating from the corners of the hexagon where the jet takes its hardest turns. These images confirm the presence of a multi-walled structure in each of the hexagon's six sides, and the structure now can be seen extending to the top of Saturn's cloud layer. The images show that the inside of the hexagon is darker than the outside. The new images also show a large spot inside the hexagon that could be related to a dark spot seen inside the hexagon in 2006 in an image taken by Cassini's VIMS instrument. An earlier Voyager mosaic showed a large spot outside the hexagon. That spot existed at least until 1991 before disappearing into the long winter polar night.

Images from Voyager and from ground-based telescopes suffered from poor viewing perspectives. In late 2006, Cassini's VIMS camera imaged the region in the thermal infrared wavelength, showing the hexagon in false color (see PIA09188). Multiple images acquired by the VIMS instrument over a 12-day period showed that the feature is nearly stationary and is likely an unusually strong pole-encircling planetary wave that extends deep into the atmosphere. Scientists had speculated that a large vortex seen outside the hexagon during the Voyager observations exerted forces on the jet stream making it adopt a hexagonal pattern in a manner similar to how jet streams on Earth divert around high-pressure systems. However, in these new images, the vortex is notably absent while the hexagon persists almost 30 years after it was first seen.

The images were taken in visible light with the Cassini spacecraft wide-angle camera on Jan. 3, 2009. The images were obtained at a distance of approximately 764,000 kilometers (475,000 miles) from Saturn. The smallest resolved features at the latitude of the hexagon have a horizontal scale of approximately 100 kilometers.

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Equinox Mission visit, and

Credit: NASA/JPL/Space Science Institute
Released: December 9, 2009 (PIA 11682)
Image/Caption Information

Alliance Member Comments
manaman (Dec 5, 2010 at 8:46 PM):
sound can makes an hexagonal pattern in fluid could its hum have anything to do with it?
marko (Jan 29, 2010 at 3:47 AM):
Carolyn "The real perplexing attribute are the sharp angles, and no one understands that yet"

Sharp angles? - easy! - I've already solved that problem with my multi-cell theory [see below]. As with soap bubbles or honeycomb, the sharp hexagonal feature is a product of pressure from (6) similar cells that surround this phenomena at lower latitude. Perhaps (Iím so modest) visible cells do not form any further down due to the combined effects of turbulence, the jet stream and the coriolis effect.

Now please excuse me - apparently I'm needed to help solve a troubling little problem called 'String theory' then Iím off to help the good people at CERN - Marko
carolyn (CICLOPS) (Jan 11, 2010 at 12:58 PM):
BuckRogers: The vortex is not spinning opposite to the winds. We are looking down on the northern pole. The winds, and the vortex, are all rotating in the counter-clockwise direction. And Webster's definition does not apply to the giant planets! As I said, the winds and the jet stream that forms the vortex are deep. The real perplexing attribute are the sharp angles, and no one understands that yet.
BuckRogers (Jan 10, 2010 at 6:42 PM):
Websterís definition of jetstream: a long narrow meandering current of high-speed winds near the tropopause blowing from a generally westerly direction and often exceeding a speed of 250 miles (402 kilometers) per hour.

Tornado : a violent destructive whirling wind accompanied by a funnel-shaped cloud that progresses in a narrow path over the land.

Carolyn: If this was a jet stream, as you mentioned, we have to think of what is happening here in order to prove the case. First I think you meant to say tornado since the vortex is obviously spinning as opposed to vertical streams of wind. Secondly, this vortex has not moved or stopped in over 67 years. Thirdly, I think the width and depth of this vortex, not to mention the micro turbulences, would be hard to explain in solely wind caused explanation.
Now letís ask some questions that will hopefully spark some other thoughts. In this animation, it appears that the vortex is spinning in the opposite direction from the way that winds spin on our northerly hemisphere and never above the Arctic Circle. Also this vortex does not progress as other tornadoes do on earth. Is this the only planet in our planet that has opposite spinning direction or in fact spinning in an opposite direction? If so, what would be the explanation? I think a strike would be the only plausible answer if this is correct.

I don't think a polar jet stream could explain or cause the great spot either or would not cause the micro turbulences going on here.
NeKto (Jan 8, 2010 at 10:20 AM):
Carolyn: i guess my confusion may be mostly a matter of vocabulary. when i see "jet stream" i think in terms of terrestrial meteorology; a phenomonon that is very narrow in width and depth, but can effect weather all the way to the surface. i can wrap my mind around several ways a jet could be caused by the hexagon, but i can't hypothesize a system where the jet causes the hexagon. then again, i am much less interested in what it is than how and why it is!
carolyn (CICLOPS) (Jan 5, 2010 at 7:17 PM):
NeKto: Why should it be so surprising that atmospheric structure is deep enoughh for the infrared instruments to see? Both VIMS (near IR) and CIRS (long wavelength IR) see banded structure at Jupiter and on Saturn. So, deep circulation features are the rule, not the exception.
NeKto (Jan 5, 2010 at 12:17 PM):
Hello Carolyn. i hope you can clarify something for me; if the hexagon is just a jet stream, why do we see it in the infrared images? if my understanding is correct, those images show structures substantially deeper than the visible light images. that is very deep for a jet stream. is it possible something at greater depth is creating the geometry that the jet stream winds its way around?
or is it more likely the jet is forming the hexagonal structures we see at geater depth?
carolyn (CICLOPS) (Jan 4, 2010 at 3:52 PM):
BuckRogers: Impact idea is not viable. Any object hitting Saturn that was big enough not to disintegrate would end up deep in the planet, not able to affect the outer layers. This is almost certainly a jet stream. Sorry. I appreciate your imaginative explanations, though. Asking questions about why what is is the way it is is where science begins.
BuckRogers (Jan 3, 2010 at 7:36 PM):
actually I think most of this crater is inside the planet and not on the outside so much. Hope I explained it properly.
BuckRogers (Jan 3, 2010 at 7:13 PM):
I have another theory as to why there may be micro cells inside a larger mega cell which all spin. Not sure if these micro cells spin in the same direction of the mega cell, but I would imagine they would.

Imagine for a moment a crater that would dwarf Olympus Mons on Mars, but having huge eruption spikes (that instantly cooled from atmosphere after magma penetration or heat from impact) coming from the center and other non smooth faces. If planet spins about or near these faces (around spikes) it may be possible to form micro cell formations (turbulences). I would also think some of these spikes or piers would be visible above cloud cover. I imagine that the very nature of powder dust, as well as spin rate, is exactly why the planet is so dusty now. Without moisture, or other moisture combining gases, it would be almost impossible for final stage of planet assimilation of dust to settle. This would hold true for other planets such as Jupiter.

Would love to hear any comments on these theories.
marko (Dec 29, 2009 at 3:41 AM):
Is it possible that we are not merely seeing a single 6-sided cell - but the interaction of a central polar cellÖ.. and 6 more that surround it? This is the usual explanation for hexagonal forms in nature [beehive, vegetation, cell division].

If so is there any additional evidence of this? - If large cells exist at lower latitudes, perhaps their relative motion is slowed by turbulence, making it harder for additional cells to form at even lower latitudes?

Or - while a form of 'fluid dynamics' these systems might be seen as "mother-cells" - fluid systems that act almost like continental drift, taking an entire sub system of storms with them on their travels round the globe? The turbulent interaction of this upper level of weather forms the banding we are more familiar with and conceals the lower structure from view.

Just a thought. Forgive me if this has already been considered and dismissed, and I have simple missed such discussion.
BuckRogers (Dec 22, 2009 at 4:18 PM):
Similar to what, Jupiter?

One more thought on my planetary strike theory... I think what hit Saturn was not very big but contained a lot of Kinetic energy.
cecalcali (Dec 22, 2009 at 9:31 AM):
CE'CALCALI dose saturn posses a simlar weather pattern and has it been seen by cassini
Pepper (Dec 21, 2009 at 11:43 AM):

I was just saying the bouncing "theroy" only for an example of what would be close to "far fetched", but still not considered impossible due to the very nature of the unknown.

The first thought I had when I read what you posted was destruction of the planet, but honestly... we have no clue at all on how much abuse a planet can take; much less the brute force it would take to make a planet turn into dust and erase it from existance. We do have theroies - but never having witnessed planet destruction, that is where they will remain.

Your theroy makes me wonder these things however. Though others (Jupiter, Uranus, and Neptune) have rings, Saturn's is the most visable to the Earthian eye, so the impact (if that's what caused it) must've been something that would upset a physicist.

Also that would give rise to another recreation of how our "big brothers & sisters" protected Earth from a mass hurling of destruction - and that one meteor either ducked & Weaved the planets, or that a fragment of a larger one, hit one of the giants - and was flung just in the right (or wrong) timeing, to hit Earth.

Just saying, I for one enjoy your theroy, though I believe that all our solar system's "big guns" took a brunt of punishment: Saturn perhaps, took a great deal more then the others. While some say Jupiter is our best guardian, perhaps Saturn needs some time in the limelight, with the phrase beneath it saying "Actions speak louder then words." :) haha
BuckRogers (Dec 20, 2009 at 0:03 AM):
Sorry but I would tend not to agree with the bouncing theory since I think this would cause planet orbit shifting or wobble, I think the event has stabilized since its stick.
Letís wonder for a minute at the other planets in the vicinity of Saturn; Jupiter, Neptune and Uranus. All planets with some sort of gas shroud around them. Of course I am only speculating because we will only know the truth if we visit these planets up close. BUT if the event I spoke of did penetrate the planet it would have made a very large impact indeed as you could imagine and kick a lot of dust into space. What IF this dust was kicked into space for millions of years and was finally absorbed by other planets. This would also mean that Saturn was much larger at one time. Could the dust from Saturnís impact cover other planets? Are these gases similar? Would this explain Saturnís large amount of moons or Jupiterís, not to mention dust rings? I would think that if the event did occur when the solar system was developing, that the gravity of these two large planets would have absorbed the smaller moons by now. I think Io has only a small amount of time left before it is absorbed but Saturn, proving how new this moon is. Would this explain why planets in this belt area small and large are covered with dust? Could an impact on Saturn explain why the planet is spinning so fast? I think it is the only explanation of why the dust is so animated. If the solar system was formed 2 billion years ago, the Saturn impact would strangely occurred about the same time as dinosaur extinction???
We might could measure the event by determining whether the orbit if Saturn is similar in roundness to Jupiter which was not hit by this same catastrophic event. Would an equator hit, of an impact this large on Saturn, caused a polar shift of rotation? Speeds in space, of this magnitude, are very likely. All you have to do is look at a supernova.
All theories of course.
Pepper (Dec 18, 2009 at 10:12 AM):
I was also going to say to your theroy Buck, that if the meteor could penetrate deep enough and perhaps hit a channel in which it was harder then the planets insides, it wouldn't even be far fetched in my eyes to say that whatever it was that crashed, is still bouncing back and fourth from "top to bottom" due to the gravitational forces. Granted it would have to be rather unrestricted - but this is why I love space, because it shows that things like a meteor bouncing from north pole to south pole, can be thought of. :)

I also love reading theroies - just as long as they don't state themselves as "fact", it is always fun to see other trains of thought; sometimes it's what's needed to get the rest of the folks going. :)
Pepper (Dec 18, 2009 at 10:06 AM):
I would think that if that were to occur the "meteor" would either have to be traveling at an incredible rate, or hitting a very soft, but firm planet. Which is completely possible due to that we really don't know anything about it's past... dare say; that we know it now.

Reading your theroy though made me think of Jupiter's big spot, although to create that.... it would've been like a planet instead of a meteor that hit - it would explain why it's dust and consistant storming doesn't stop either, especially if something that big still exists on it's surface, even if in peieces or one big lump.

Reading upon the "Ancient Skys" it's no secret that there may have been different "planets" (poor Pluto) that roamed the sky, and leave no trace because ... maybe they crashed into our giants, and didn't have good insurence. :)
BuckRogers (Dec 16, 2009 at 9:41 PM):
I was watching an animation just now of the clouds and rotations on Saturn. It appears that that meteorite could have fractured on impact and caused smaller crust extrusions throughout the surface in many spots, and would lead to further proof this case.
Do you think this is totaly off base?
BuckRogers (Dec 16, 2009 at 9:26 PM):
My guess would be a meteorite hit that and almost extended through the planet. This is like a water vortex, mainly because of its duration. With a catastrophe like this, I wouldn't look for this to end in over 200 million years unless 2 things happen. Cooling of the planets core which is causing a super cooling in the magma from outside atmospheric temperatures, or dust from the ďcloudsĒ clogs the hole from the outgassing area (the big spot). If this is the case, the planet core is probably already pretty cold.
My guess is, that a meteorite came in, struck the planet, deflected off the core, almost penetrated the crust and caused the big red spot on the equator side. My guess is there is an outward bulge on the big black spot from out gassing. This could explain the large amount of moons and dust ring, why it is so cold, why the dust never settles and the reason the big spot never moves.

Just a guess, as far fetched as it seems.
NeKto (Dec 15, 2009 at 4:53 PM):
I would love to see what differences if any the north polar vortex shows compared to the south pole. i also wish i could edit some of the misspellings i missed last post (sorry CaRolyn)
i had the thought that perhaps the hexagon is stable just from the natural stability of the shape itself. then the question becomes; what initiated it? are we going to have enough information on this mystery for an article in "Science" or "Scientific American" any time soon?
I M; looks like i was of 3 orders of magnitude off on my allen key guess!
Pepper (Dec 14, 2009 at 9:38 AM):
I didn't expect to see so many tornados in the center, I wonder if those are caused by whatever is making the shape... or if they are making it. The big area that didn't turn out for the cameras is prolly a tornado too... *mumbles* Tornados are always up to no good! :p Taking houses first, making shapes and now blurrin' our camera feeds!

Thanks for puttin the clips up! It's cool to see how truely different and unique Saturn remains to be. :)
NeKto (Dec 13, 2009 at 1:10 PM):
Thank you Caolyn. i read the release. the big hex sure is big. i will be happy to see any of the science that comes from the image information. i can't think of another bit of weather in our solar system that come close to being as bafling as Saturn's hexagon.
also read the release on Iapatus. hope to read the articles in "Science" soon.
Steve Albers (Dec 13, 2009 at 8:52 AM):
Is this similar to Rossby waves on the Earth? If such waves are embedded in a high latitude jet stream, the inward sides would be fairly straight making it look like polygon. In this case a hexagon.
Bicycle81 (Dec 12, 2009 at 6:41 PM):
AWESOME display of observation data! This thing rather looks like the end view of a tapered roller bearing assembly. The hexagon jet being the inner race, somewhat brinelled, six places. The six rollers are a little nebulous but pinned in place on the centerlines of the flats, but radially offset. The outer race is an anti-circulation jetstream around the extreme outer limit of the image . There may be some reason that a fluid with certain densities in a planet with certain gravity and diameter would reach a stable dynamic equilibrium with six vortices between two counter-rotating jetstreams. Jupiter has demonstrated that vortices can be persistent. However, the persistence of 6 adjacent vortices would be something else!
carolyn (CICLOPS) (Dec 12, 2009 at 5:13 PM):
NeKto: You should read the press release under Newsroom: "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)."
NeKto (Dec 12, 2009 at 1:30 PM):
I M; do you think a 1.7*10^13mm Allen key would be in the ball park?
But Really, Carolyn, if you folks on the Team could give us an aproximate dimention for the big hex i for one would greatly appreciate it. must take an aweful big swizzle stick to stir that drink.
the more i see it, the more it reminds me of blending something in the kitchen where the "mix" is moving at different speeds.
Another great set of images Team! thanks again!
Troubled Tribble (Dec 10, 2009 at 1:00 PM):
I've looked at the short movie numerous times. Seems to me that this phenomeon changes shapes more than it remains a constant hexagon. There appears to be a tear drop, a circle and the now famous hex. What causes this is open to suppostion. For myself it could be magnetic fields, solar winds or God just getting our attention, so that we will scratch our collective heads.
bousharde (Dec 10, 2009 at 6:36 AM):
I'll leave the theory to others and just marvel at the beauty of nature. No explanation needed. =)
Red_dragon (Dec 10, 2009 at 3:24 AM):
Amazing work!. And the best is still to come if there's a Solstice mission (hope so).
Iapetus Monolith (Dec 9, 2009 at 3:33 PM):
What size hex key would fit snugly in there?

"Give me an Allen wrench large enough ... and I shall stop the gas giant" -- mechanical engineer with delusions of grandeur (with apologies to Archimedes)
three_sixteen (Dec 9, 2009 at 1:13 PM):
Love it!

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