Faint Ring Thread, Saturn's D, E and G rings Options

[ugordan]

if it's a moonlet why haven't we seen it already?

My guess would be phase angle. Both the Aug 15th and 22nd observations were done at low phase angles where a solid object would back-scatter light. If the majority of G ring imagery in the past was high phase (optimized for actual particles which forward-scatter light) it would be hard to pick up a small crescent bathed in scattered light of the particle clump.

This, on the other hand, looks like ideal viewing conditions for a solid object. My money's on a small moonlet.

[jasedm]

The follow-up observations lend weight to the idea that it's a moonlet, perhaps suspected from earlier imaging campaigns of that region of the D-ring.
What of the fact that it's well inside the Roche limit though??

[ugordan]

We're talking about the G ring.

[jasedm]

Oops, getting my rings mixed up

[Juramike]

Oops, getting my rings mixed up

That's always dangerous

[Floyd]

No G-Ring images on the August 29th (unless I missed something). Maybe they will take some tomorrow on the 5th. Would be nice to get an image targeting/tracking the G-Ring object/clump.

[Ken90000]

Aren't we still in Solar Conjunction?

[Floyd]

Yes we are in conjunction, but comming out.
There is a very nice Cassini News report on rings and ring arcs associated with small Saturn moons.
On the G-Ring they state:

"This is probably the same mechanism responsible for producing the arc in the G ring," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. Hedman and his Cassini imaging team colleagues previously determined that the G-ring arc is maintained by a gravitational resonance with Mimas, much like the new, small moon arcs. "Indeed, the Anthe arc may be similar to the debris we see in the G-ring arc, where the largest particles are clearly visible. One might even speculate that if Anthe were shattered, its debris might form a structure much like the G ring," Hedman said.

I still wonder if the image of the G-Ring object was smeared because it is an extended clump, or if the image was not targeted to track the rotation of the ring.
-Floyd

[Floyd]

Nice image of Anthe arc from the news writeup.

"The moon is moving downward and to the right in this perspective. In this image, most of the visible material in the arc lies ahead of Anthe (2 kilometers, or 1 mile across) in its orbit. However, over time the moon drifts slowly back and forth with respect to the arc. The arc extends over about 20 degrees in longitude (about 5.5 percent of Anthe's orbit) and appears to be associated with a gravitational resonance caused by the moon Mimas. Micrometeoroid impacts on Anthe are the likely source of the arc material. The orbit of Anthe lies between the larger moons Mimas and Enceladus."

[Floyd]

According to Ciclops Looking Ahead for Rev 84, on September 13th, "Cassini will then observe an arc of material in the G ring that was recently observed to have a denser clump of material within it."
We should know more soon.

[Floyd]

I can't see any clumps of interest in the G-Ring images from September 13 & 14. The 13th's images are almost edge on and the 14th's have so much camera flair that I can't even find the G-ring. I'm sure the Cassini team can subtract out the flair, so there is probably good information somewhere in the images.

[Floyd]

Some nice images of Ering which sure look a lot like the Gring. "Taken on October 27, 2008 and received on Earth October 28, 2008. The camera was pointing toward SATURN-ERING at approximately 1,199,543 kilometers away". I've seen pictures of the Ering with Enceladus embedded. This set of three has a nice moving clump--which made me think it the the Gring and clump. Looks like the Ering has both Enceladus and a clump. Open all three images in tabs and flip through to see the climp and stars move.
Image1
Image2
Image3

[volcanopele]

No, that's definitely the G ring. Not sure why it is labeled as the E ring though.

[ngunn]

Nice bump with shadow:
http://saturn.jpl.nasa.gov/multimedia/imag...6/N00125063.jpg

[Phil Stooke]

A bit late - but that E-ring image is presumably labelled E-ring because it's centered on the E-ring. The label tells you what the camera is pointed at, regardless of what else might be in the image.

Phil