Slashdot Mirror
Saturn Rings But No Spokes
An anonymous reader writes "Scientists continue to ponder why images of Saturn's rings today lack the 'spokes' or dark radial bands radiating outward and first observed on the Voyager flyby. The Boulder-based Cassini Image Team describes 5 visible moons, plans for the descent probe going into the Titan moon's hydrocarbon-rich atmosphere and the expected orbital entry around Saturn less than 4 months from now."
There were no real current Astonomy Picture of the Day references so I linked to a search on Saturn. This gives quite a few different views of Saturn and some other related material as well.
Use your head, can't you, use your head,
You're on earth, there's no cure for that - S. Beckett
By the way, next summer NASA's Cassini spacecraft, launched in 1997, is scheduled to go into orbit around Saturn and its moons for about four years.
The piggybacking Huygens probe is scheduled to go into the hazy Titan atmosphere and land on the moon's surface (if all goes well). The Huygens probe is geared primarily towards sampling atmosphere. The probe is equipped to take measurements and record images for up to 30 minutes on the surface. But the probe has no legs, so when it sets down on Titan's surface its orientation will be random. And its landing may not be by a site bearing organics.
Please help publicise swpat.org - the software patents wiki
I think they mean the itty-bitty breaks in the rings that you can see if you look very close. (There's one just about in the very center of the image.)
The "spokes" are odd disruptions in the rings caused by Saturn's magnetic field rotating through them. They show up as dark patches radiating directly away from Saturn or occasionally arching, and they travel like a wave around Saturn in time with its rotation. It was this timing/speed that tipped astronomers off as to what was causing them, incidentally.
So if the spokes aren't visible now, maybe Saturn's magnetic field is fluctuating/less coherent than normal. It's a gas giant so its field could be less stable than the denser planets. There may be some low-level eg mid-atmosphere storm disrupting the normal field-generating circulations.
Just a thought. IANAA
cheers, Sal
--
Sal
Writings: saltation.blogspot.com
Wravings: go-blog-go.blogspot.com
Perhaps the spokes don't show up because they're not applying those same techniques? I certainly don't see any mention of those techniques in the article in the first link.
libertarianswag.com
This is an offtopic comment: offtopic because it was stolen verbatim from a totally unrelated story:
8 6& cid=7019194
.sig modded up
http://science.slashdot.org/comments.pl?sid=793
It's just an excuse to get the
Okay, I was wondering... although it looks like it could easily be something on the lens. Heck, it almost looks like what we call a 'density dot' at work. (Explanation: I work at a copy shop, and when doing colour copies, sometimes the toner will not be applied evenly, leaving small blank or lighter shaded dots in the middle of coloured areas.)
But it couldn't be a density dot because the imaging would have been sent back from the probe using radio signals, right? It's not like a radio signal gets a bad spot on a belt.... and interference would have produced a much more distorted image....
Hrm...
Kierthos
Mr. Hu is not a ninja.
Why was this modded offtopic? I'm guessing the moderator didn't recognize what he was talking about. I was actually looking to see if there was a Fithp post before I posted.
Background, in the Niven book 'Footfall', the first indications they see of the incoming alien invasion is weird, spoke-like distortions in the rings of Saturn.
Google it.
Here
Here
Here (scroll down to find a movie)
Perhaps it is just a bad picture, Nasa has a much clearer one. I don't see anything like that on the picture linked in the article, but maybe I'm just missing it.
Here is a link to Voyager spoke images
Single Image
Gallary
Table-ized A.I.
In all the APOD picture of Saturn I found a reference to Spokes and a picture that contains them.
Use your head, can't you, use your head,
You're on earth, there's no cure for that - S. Beckett
To all,
I am the leader of the Cassini Imaging Team, and came upon the discussion all of you are having about spokes. The image that you have linked to does not clearly show spokes -- so it's not a good example -- and the caption at JPL is wrong: it was *not* the first time spokes were seen by Voyager. Voyager 1 first saw spokes on approach to Saturn, when the resolution was comparable to what Cassini is seeing now.
We're not sure if spokes are a seasonal phenomenon, or their visibility is very sensitive to viewing geometry. We will find out though, since Cassini will remain in orbit and make observations for 4+ years.
So stay tuned.
- Carolyn Porco
Cassini Imaging Team
I was a young engineer at JPL when Voyager 2 encountered Saturn, and I remember when the first photos of the spokes in the rings were displayed in real time on the monitors in the cafeteria. The work on other projects had pretty much ground to a halt while everyone watched the data come in.
Of course, the real time data had no captions, no explanations of what we were seeing, so we had all sorts of guesses - density waves, camera artifact, etc. Once it was apparent that the waves were holding together as the rings rotated and were not being sheared apart, it was clear they were not due to any gravitational effect. Since they moved with the rotation of the planet, the accepted explanation is the magnetic field of Saturn causing the charged dust in the rings to concentrate into visible spokes. As I understand it, the spokes are not a wave phenomenon at all.
We're not sure if spokes are a seasonal phenomenon
Just to clarify what he means here:
When the Voyagers were imaging the spokes in about 1980, the Saturnian ring system was nearly edge-on to the Sun. Now that Cassini is approaching Saturn, the ring system is wide open. It is natural to suppose that the edge-on rings made the spokes visible with long shadows, and the face-on rings make the spokes less visible.
The only thing necessary for the triumph of evil is for good men to do nothing. - Edmund Burke