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

[Rob Pinnegar]

There are two new "Raw Images" up that give a good view of Saturn's D Ring. As of today (July 17th) they are on the first page of the Raw Images section. The better of the two is image number W00009347.

The very narrow inner ringlet is called D68 and it is the innermost well defined ringlet of the entire ring system -- it's only about 7250 kilometres above the cloud tops, about half-way from the planet to the inner edge of the C Ring. If you search the "Saturn-D Ring" section of Raw Images, there is a nice narrow angle view (N00035241) which I am pretty sure is a close-up of D68. D68 is an oddball, it really is sort of "in the middle of nowhere".

The brighter ringlet in the upper right is called D73. About a thousand kilometres inward from D73, there is a noticeable "dark zone". In the Voyager images, there was a third bright narrow ringlet inside this zone, D72, which seems to be gone now, strangely enough. The relevant Voyager images are Voyager 1 image 34946.50, and Voyager 2 image 44007.53. If the diffuse ringlet at the inner edge of the "dark zone" is what is left of D72, it looks to have migrated a bit closer to Saturn in addition to spreading out a lot. (By the way, I'm not making up these ringlet designations on the fly -- they are given in a paper by Mark Showalter that was published in Icarus in 1996, which is pretty much the only major paper on the D Ring.)

To give some idea of scale, the three bands of material in the far upper right corner are part of the innermost ringlet of the C Ring (this can also be seen on some images of the rings taken on May 3rd of this year).

Since it is so faint and doesn't appear in many images, the D Ring rarely attracts much attention. But it's kind of neat to look at if you haven't seen it before, particularly because of D68, which is sort of the "anti-F ring" in a way.

[ugordan]

Again, a shot of the clump/moonlet in the G ring, slightly motion-smeared: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00128611.jpg
Not as obvious as some other shots, but it's still there and, apparently, persistent.

No official word on this yet?

[volcanopele]

Tiny Moonlet Within G Ring Arc
http://ciclops.org/view/5493/Tiny_Moonlet_Within_G_Ring_Arc

The discovery of the G ring arc moonlet has been officially announced via a press release and an IAU Circular.

[stevesliva]

...and I just read about it on Emily's blog.

How close are the G-arc flybys mentioned just recently here?
http://planetary.org/blog/article/00001857/

Has the first already happened? Doesn't sound like it will look like much even relatively close.

[volcanopele]

The one in January 2010 is in the 10000-20000 km range (Celestia gives me ~14000 km). At that distance, S/ 2008 S 1 should be about 6 pixels across. The other would be in February 2017 at 20000-30000 km.

[elakdawalla]

Huh, I didn't realize you could get that close to the G ring. Are there plans actually to attempt to image S/2008 S1?

[volcanopele]

We are nicely out of the ring plane at the time, so it should be fine.

[nprev]

Just restating congrats to Gordan for spotting this moonlet in what are probably the discovery images...what an eye!!!

[ustrax]

Just restating congrats to Gordan for spotting this moonlet in what are probably the discovery images...what an eye!!!

Maybe I've missed something but are you saying that it was Gordan who spotted it first?...

made a gif out of the announcement images:
http://www.gifninja.com/Workspace/e6c3d462...3422/output.gif

[ugordan]

Maybe I've missed something but are you saying that it was Gordan who spotted it first?...

I think Nick is referring to this post. The raw image links apparently don't work anymore since the page redesign, but it's the same images as in the release.

[canis_minor]

FYI next Wednesday is a close encounter to Aegaeon (closest until 2015), the parent body within the G ring. Close approach should be about 13,000 or so km and images will be taken near ~ 90 deg phase. I'm divided between thinking that these images will be vanilla, noisy images like many Cassini has taken before, or potentially spectacular. Should be worth a look though. Tracking pass begins 11:30PM UK time, 3:30PM Pacific. - Cheers.

[dilo]

On April 18 Cassini made an interesting sequence of images of E-ring and main ring halo (see http://saturn.jpl.nasa.gov/photos/raw/?sta...toredQ=2225395).
Using 3 consecutive clean-filter images with different exposures (W00063561/2/3), I made this false color "HDR" composition (red=darkest, blue=bright - solarization used too):

Attached thumbnail(s)

 

[stevesliva]

Oddly, I think, the Cassini status noted this:

Friday, July 30 (DOY 211)

The S61 sequence concluded and S62 began execution today at 2010-211T18:51:00. The sequence will run for 37 days and conclude on Sept. 6. During that time there will be one targeted encounter of Enceladus and eighteen non-targeted flybys ­ two each of Titan, Dione, and Epimetheus, and one each of Calypso, Atlas, Pandora, Daphnis, Janus, Pan, Tethys, Polydeuces, Telesto, Prometheus, G_ARC, and Aegaeon. Three OTMs are scheduled, numbered 259 through 261.

I thought 'G arc' and 'Aegaeon' would be the same thing??

[Hungry4info]

Agaeon is a satellite, the G-arc is a ringlet.

[geckzilla]

A quick, probably simple question... I wondered if this is a more or less correct guess: Are the E and G rings are kind of reflective or glossy like snowflakes? I see the way they are illuminated in the famous Saturn ring portraits and the bright points line up with the sun in the same way a glossy reflection would. The rings are of course made of many particles so the effect is diffuse and smooth. I circled what I am describing in the picture to ensure there is no confusion about what I am asking.

As a way to teach myself how to use Blender effectively I have been trying to copy various physical effects. I found that a good way to simulate the outer rings was with a hacked glossy material (I can't make a glossy volume...). My fake Saturn is here if you are curious. (If Björn Jónsson happens to read this, you are awesome and I thank you for providing all those image maps.)

[john_s]

"Glossy" is the wrong word- that implies a specular (mirror-like) reflection. What's going on in this image instead is that there are small particles in the G and E rings which become particularly bright when the sun is almost directly behind them (in the same way that smoke is most conspicuous when backlit by the sun). The parts of those rings that are closest to being exactly backlit are the brightest, and those parts are close to Saturn, because the Sun is behind Saturn.

John