The Return of Saturn's Spokes

CheshireCatCO writes "After more than a year in orbit around Saturn, the Cassini spacecraft has finally spotted 'spokes' in the rings. Spokes, large radial structures in the rings, where seen by the Voyager spacecraft and have remained difficult to fully explain. The reappearce of the spokes comes about two years earlier than many models predicted."

Comments

See Cassini's path

[latent_biologist]

"Unlike Voyager or Hubble, Cassini is in a unique position to study ring spoke phenomena at Saturn."

With Celestia, you can actually follow Cassini's path as it follows Saturn. It really puts the above statement in perspective (plus it makes u feel like an astronaut).

Ring Object Size

[williwilli]

While I understand your concept, another poster suggested the rings are made of smoke sized particles. Actually, the particles are sometimes quite large according to this page:

More recently, astronomers bouncing radar off the rings and analyzing the reflected signal found that ring particles must be from a few centimeters to a few meters across. When the Voyager spacecraft went behind the rings with respect to the Earth, astronomers could measure the particles sizes from how Voyager's radio signal scattered off the particles and from how sunlight scattered through the rings. The ring particles range in size from the size of a small grain of sand to the size of a large house, but on average, they are about the size of your clenched fist. Spectroscopy of the rings shows that the particles are made of frozen water. Collisions between the ring particles keeps the ring system very flat and all of the particle orbits circular.

from http://www.astronomynotes.com/solarsys/s16.htm

though there may be other information available which I am unaware of, of course. But if this particle size stands, it seems a fairly simple explaination that a meteroid could hit a large ring object and cascade debris and impact effects throughout the rings themselves...

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Re:Cause of the spokes?

[CheshireCatCO]

In a word, no.
The spokes must be tied to the magnetic field of Saturn. This explains why the stay at the same magnetic longitude of the planet and why they don't wind up as the inner parts of the rings orbit the planet faster. So they're not disturbances in the ring particles themselves, since the ring particles are too massive to really feel the magnetic field.

However, if you levitated dust over the rings, that would do the trick. The problem is how to levitate the dust. It turns out that you can develop a negative potential on the rings (I think it's negative... I forget, to be honest) which can repel the dust and cause it to hover. So under the right conditions, if dust were kicked up by a small collision in ther rings (say a meteroid collision), it can float over the rings and spread radially, making a spoke.

Or so we think...

Spoke mechanism

[Anonymous Coward]

The theory I heard is that the ring particles pick up a charge from being bombarded by particles trapped in the radiation belts. When a meteoroid plows through them, it breaks small, dust-like particles off. Being light and charged, these particles are picked up by the rotating magnetic field and circle the planet as a radial spoke. As the charge leaks off of the dust, the dust particles go into normal orbits with the ones farther in orbiting faster, so the spoke spreads out into a wedge and then dissipates.

Re:Artifacts?

[CheshireCatCO]

There's nothing that we do that would lead to radial features. Especially across multiple images at consistent magnetic longitudes. Also, these have been seen by at least three or four cameras, now. So it's hard to imagine these being artifacts.

(In fact, the images on the space.com site might even be the raw images.)