Not only are we seeing the long shadows of moons on the rings, but objects in the rings are now casting shadows. Link

Notice the mini shadows on the bright twisted band just where the moon shadow ends.

One of you who is more adept at image cropping may want to post a cropped blowup.

Nice catch! You have just discovered 11,821 new moonlets!

(x2, rot 18 degrees, crop)

Click to view attachment

(Credit: NASA / JPL / SSI)

That ring seems to have many more large boulders than the others in frame - its amazing how chaotic it is.

Adjacent frames show the speed the long shadows move:
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00133375.jpg

The large moon shadow here nicely maps out the shape/thickness of the rings:
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00133376.jpg

The Cassini team are going to have fun finding classical names for all those moons..

Wow - is this the region periodically disturbed by the resonance with Mimas? That would certainly help explain the chaotic appearance of that ringlet.

Pretty neat. They almost look like the shadow of a mountain range. Actually though are we seeing the shadows of ring irregularities instead? I would think the actual moonlets would usually be too small to resolve. Maybe we're seeing clumps of moonlets that are being warped away from the ring plane (or perhaps simply more dense than the surroundings).

Steve

Wow, that's seriously wicked. Nice catch, Floyd!

Thanks for catching that Floyd. This is amazing. I am utterly fascinated with ring particles and the subtle gravitational phenomena associated with so many distinct masses interacting.

I would think a careful examination of the elongated size and shape of those shadows would result in important data ripe for a new paper on particle size and density.

This is a rough attempt at an animation using frames N00133373.jpg, N00133374.jpg, N00133375.jpg

(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS49/N00133374.jpg etc)

Click to view attachment

(Credit: NASA / JPL / SSI)

There is a little movement in the shadows between frames, I was hoping for more.

Thanks sci44 for the crop and the movie. I am also surprised at how little the mini shadows change.

It's not all that surprising if we assume that there is very little relative motion between the particles which I'd assume is generally the case unless there's a moonlet nearby disturbing things. Taking an 80000km altitude for the rings (which may be a bit off but it serves for general argument) - the orbital velocity of the particles is around 13km/sec. At that altitude 1 second of arc is remarkably close to 1km so you'd need almost 11 minutes between images to have the particles move by a degree along their orbit.

Excellent finding, Floyd!

Ian, this is clearly the outer edge of B-ring, where particles are in 1:2 resonance with Mimas. The resonance causes Mimas' pulls on these ring particles to accumulate, destabilizing their orbits and leading to a sharp cutoff in ring density. These elevated structures could be eventually related to the relatively high inclination of Mimas orbit (1.57°) or to low velocity impacts in such dense region. Just two ideas...
It would be nice to have an estimated height of such features based on shadow lenght... any support on this?

Yes, an excellent find, Floyd!
The first frame of that anim is a bit out - I am sure one of the more experienced UMSF'ers can make a properly calibrated/cleaned up version..
Just watching that GIF - there is actually a trail of disturbance on the left third - from the edge of the ring cutting into the main ring plane - deeper as you go to the left - like the trail of something plowing into the ring at a very shallow angle? Strange. Are these large boulders, or loose collections of small particles? Electrostatic charges are said to play a role with structures like the ring-spokes - is that a factor here? I don't know..

By the way, the sequence of 14 (incrementally numbered) frames with the shadow of (Titan?) cutting across the rings, from
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00133399.jpg
through to
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00133412.jpg
is crying out for an animation - now if only there was an animator here..

Most of the moon shadow stuff at the moment is either from Mimas or Tethys.

Very cool animations everyone!

With Cassini's motion, this is not an easy set of images to register.
Here's my attempt at an animation.
Hard to see if any changes are 'real', 'imagined' or 'artifact'.
Click to view attachment

All I got to say is WOW, you guys...

Astro, how many minutes does your animation span? (I'm thinking that it must be a fairly hefty period--15 min more or less?--given that moon shadow passing in & out of the FOV.) If that's true, then it's really striking how stable the "mountain silhouette" ring particle shadow pattern remains throughout the period.

Using the word "striking" because my gut feeling (and I'm probably not alone here) was that the rings' behavior must be pretty chaotic at the particle-level scale. That well may be, but not over as short a time scale as might be assumed. Should this be obvious in retrospect?

Just to blue-sky a bit, what if the "chaos threshold" is lower than we expect? By this I mean that perhaps the major ring particles (say 10m or larger) in at least this segment of the ring system have achieved some sort of dynamic equilibrium over time so that they really don't bounce around much relative to their neighbors. It sounds thin to me, too, but you'd think that the system would tend to evolve towards a low-energy state like that over time.

I would imagine that the Mimas/Tethys shadows(s) should provide a relative scale to calculate the sizes and the size distribution in that segment. The ratio of the diameter of Mimas to the triangle it's shadow creates should be the same as the ratio of these smaller objects. I wish I had the time to do this myself.

nprev...not sure what time period. Someone here will be able to tell us I'm sure.

On the 'real' or 'imagined' question...
Take a look at this animation, looking at a small segment of larger version.
Click to view attachment

Right in the middle there seems to be some large 'particles' that tumble and I'm guessing that their corresponding shadows are also visible against the 'lit' ring structure in the background. Thoughts?

These images are amazing - I think they might be the most interesting images of the rings since SOI. Knowledge of the rings' 3D structure is about to be revolutionized. And let's not forget that these shadow will get much longer in the coming months.

Some quick 'back of the envelope' calculations: The solar elevation angle is ~1.9 degrees. Assuming that the shadows lie on a perfectly flat surface that is not tilted relative to Saturn's equatorial plane they are ~30 times longer than the height of the features that cause them. The length of the largest shadows is ~15 pixels. Assuming that the range is ~1.1 million km ("The camera was pointing toward SATURN-RINGS at approximately 1,138,888 kilometers away") and that Cassini is directly above the shadows (definitely not the case) the length of the shadow is ~100 km and the height of the feature casting the shadow ~3 km.

This is highly approximate but indicates that the highest 'peaks' are probably a few km high.

Ring dynamics are slightly beyond me (I'm a microbiologist), but if we think in terms of large boulders or small moons, and the boulder-boulder gravity interaction is small, then each is in its own eliptical orbit. So a boulder we see highest above the ring plane/with the longest shadow will drop down to the lowest point below the ring plane 180 degrees later. If one assumed that the boulders' phase and inclination are all random, then you would have the boulders all moving around relative to one another, but you would need to observe them through about 90 degrees of orbit to see really significant changes--and then the shadows would have rotated 90 degrees. So the question is, what size changes could you see in 45, 22.5, or 11.25 degrees of orbit? A shadow could at maximum shorten or lengthen by sine of the angle. Maybe 22.5 degrees is small enough to keep track of shadows and register images and big enough to measure changes.
Any of you with real knowedge of astrophysics/ring dynamics--please correct my physics I reasoning.

Astro0 I took the liberty of stabilizing your animated gif since I have found in the past (with one of Stu's originally) that the jumping around has a way of distracting from the actual changes.

A lot of it looks like it has to do with the lower resolving threshold of the optics interacting with the collector grid (or else the jpeg compression), but I do think I still see the "tumbling" effect on the larger particle right of center. It also might be a change of perspective among two or more visually aligned chunks, as the ring and Cassini pass each other. The full res images of this sequence whenever they are released will certainly be interesting.

I agree, Dan. There are certainly relative motion & differential illumination effects at work in addition to the performance limitations of the optics, and it's very hard to tell what's "real" from this raw data other than the shadows.

Definitely looking forward to more!!!

Nice work Dan

I hope that we can look forward to even better images like these.

If all continues to go well, the XXM plans will certainly produce some exciting, close-up images.

[temporarily deleted]

Hmm. I wonder how this "scoop" will go by some imaging team members...

Well...EDITED: Let's wait and see...

Don't miss Emily's great piece on this, with angles and heights. There must be quite a pile-up at the outer edge of that ring. Does it go all the way round?

I'm not normally a ring watcher, but this is the start of something not to be missed. It's eyes down for the magic shadow show.

Thats a fair point - I have nothing but respect for the work the Cassini imaging team, and they should get first stab at the data - I chopped my last post, but shall I just say I recommend N00133374.jpg as deserving close study (especially the left hand side of the region in question)..

Just because I felt like linking to a random recent image of the rings, here's one. Beautiful!!!!

I just read Emily's excellent blog post and I have to say that she makes a good argument for the shadow causing features being a couple of km in height. I also have to say that my earlier comment where I said I thought it was unlikely that we should expect to see motion was off base - I was ignoring the frame of reference and target of the camera and I was not factoring in the nature of the disturbance that Mimas would be causing. I'm very keen to find out what the Cassini team has to say about these shadows in any case.

Emily's piece on this is simply outstanding, a great piece of science journalism. It made this fascinating topic a LOT easier to understand for me. Thanks Emily!

( ... but then you go and ruin it by mentioning that ******* song at the end! It's 06.50 here in the UK right now, I'm just about to head out the door to go to work, and I know that tune will be going round and round in my head all freaking day now... !!! )

Just to put one final piece into this thread, here's a rough stitch of the images across the rings.
I've left the moon shadow from each image for effect.
When everything is in context it certainly makes for a pretty picture.
Click to view attachment

Try rotating the image for a completely different feel on the shadows.

I'm starting to think that we were definitely 'seeing more' than is actually there.
But how fascinating is it to contemplate the day when Cassini does get a close enough view of the ring structure and with enough images together to 'actually see' the particles move.

Astro0

That's cool, Astro0, thanks for that. Although the edge of the B ring is the most "mountainous" place in your pan, when I wander around it I see some other noisier-looking spots -- I wonder if those are places where there's some topography to the rings.

--Emily

(P.S. Thanks, Stu. Having all of y'all's commentaries to start from makes things easy.)

These are ridiculously spectacular images. Sorry if someone has already mentioned this, but there appears to be a correlation between the length of the ring shadow and the brightness of clumps in this ring, which certainly makes sense.

We can also obtain information about the extent of structures perpendicular to the rings elsewhere, by the absence of visible shadows. Where we can't see ring shadows, any shadow present must have a length of order 1 pixel or less. Using the figures quoted above (7 km/pixel scale, 1.9 degree sun angle), that means any structures elsewhere must be less than roughly 200 metres in height. Of course this limit will improve as the sun angle decreases...

When CASSINI launched I never expected THIS!

A leapin and hoppin on a moom shadow ......... (thanks for that Emily... have not listened to the Cat in years)...
SO... just cannot stop the leapin and hoppin in my minds eye now.. a rainbow bridge of cascading light and shadows, along a bumpy grainy plain that sails off to the limits of our current vision.....

I am blown away.... how grand!!!!

Craig

APOD today. The 'preliminary hypothesis' link goes to Emily's blog, and 'jagged shadows' comes straight here.

EDIT: Oh no . . . the 'cast' link goes to Cat Stevens . . .

Here's another calculation. I wanted to know roughly how fast the relative motions are between these jostling clumps.

Taking the peak amplitude of the displacement from the ring plane as 2 km and the radius and orbital velocity of the outer B ring as 117600 km and 17970 m/s respectively I get:

Maximum perpendicular velocity (whilst crossing the ring plane) = 2 x 17970 / 117600 = 0.3 m/s.

So, even for particles or clumps rising and falling exactly in antiphase, collision velocities would be less than 1 m/s.

Makes you realise just how gentle most of the rest of the rings must be.

A few years ago the BBC produced a series called "Space Odyssey" (re-christened "Voyage To The Planets" for overseas markets) and while it wasn't 10000% accurate scientifically, it did feature some truly breathtaking images and visuals, such as an astronaut flying through Saturn's rings...

http://www.youtube.com/watch?v=tTrh26hBUlQ

The Saturn's rings EVA begins at 4.53 if you want to skip to that part.

The series got quite a lot of stick for being cheesy and melodramatic, but I've watched it again and again, just because it inspires such wonder when I do. Well worth checking out the DVD, or trawling YouTube for the rest of it.

Hey, that is indeed a beautiful animation of the ring particles, thanks Stu. (Best watched with the sound off though.)

The great wall of Saturn...

At the right side of the third frame there's a round spot, as if a free moonlet was casting a shadow on the wall of dust. To the left of it, a pillar of dust and its shadow seems to appear.

Click to view attachment

Uh oh....

Just noticed that myself and was going to post, but I see you beat me to it. Good observation. I think the background shadow you are attributing to the "pillar" might actually be the shadow of the moonlet instead. The shadows should appear at an angle to the corresponding foreground objects since this section of the ring is not directly parallel to the sun. Just my thoughts.

I don't see it. All I see is the resize filter smoothing out unresolvable pixel values. A dark pixel inside a brighter area will tend to look circular, especially with the bicubic resample filter.

I haven't done my own processing yet, but it appears it might be in the other images and moving. I don't know the time separation between the images so it's difficult to tell if the apparent object is moving at a constant rate. What caught my initial attention was the appearance of what appears to be a corresponding shadow in the last frame at an angle consistent with the shadows of the other ring objects. I agree though, with the resolution we have it could just be an illusion or a artifact of the image processing.

OK, after further review I concur it's a processing artifact.

I was going to say that..

I started this thread because I was really blown away by the images of the outer edge of the B ring. I correctly guessed that many UMSFers would be fascinated as well. However, I didn't (and don't) believe finding the images scooped the Cassini team in any way. They had predicted that protuberances in the rings would cast informative shadows. See the following Cyclops news release of March 23, 2009.LINK

Excerpts from the Cyclops news release:
[During equinox, Saturn's moons can shadow the rings], especially those whose orbits are inclined with respect to the equator, begin to intersect the planet's rings. When this occurs, the equinox period has essentially begun, and any vertical protuberances within the rings, including small embedded moons and narrow vertical warps in the rings, will also cast shadows on the rings. At exactly the moment of equinox, the shadows of the rings on the planet will be confined to a thin line around Saturn's equator and the rings themselves will go dark, being illuminated only on their edge. The next equinox on Saturn, when the sun will pass from south to north, is Aug. 11, 2009. … Because of these unique illumination circumstances, Cassini imaging scientists have been eager to observe the planet and its rings around the time of equinox, and Cassini's first extended mission, which began on July 1, 2008, and extends to Sept. 30, 2010, was intended to gather observations during this time. Hence, its name: Cassini Equinox Misson. … Cassini imaging scientists first predicted when and where the moons' shadows would fall on the rings and then planned special imaging sequences to target those locations. … More than just pretty pictures, these observations and others to come could provide valuable information regarding the presence of any deviations across the rings from a perfectly flat wafer-like disk. Working outward from the planet, the main rings are named C, B, and A. Saturn's ring system is wide, spanning hundreds of thousands of miles or kilometers. But the main rings are perhaps only 10 meters (30 feet) thick, and they lie inside the F ring which is vertically thicker than the A, B and C rings, making the determination of interior vertical deviations difficult when imaging the rings edge-on.

Assuming Bjorn Jonsson's calculations are correct (post 17), the outer edge of the B ring is warped approximately 3 km which is large compared to 10 meter ring thickness mention above. We at UMSF are certainly having a lively discussion and doing great things with the images, but I am quite sure that the Cassini team recognized the significance of these images as soon as they hit the ground. It may take the scientists a while to comment, but I'm sure they are all over this and planning additional sequences to get just the right images for publication.

Perfectly said Floyd.

For the majority of contributors, UMSF'ers are armchair explorers only and for us it's just fun to ponder the possibilities and guess at what we are seeing. The Cassini team like all the other mission scientists and engineers are the experts, and they tell us the facts when they know them. We respect and appreciate the fact that they even share this data with the public at all. For the moment, we are just the wide-eyed audience on the outside looking at the magic they produce.

More vertical relief here?
http://saturn.jpl.nasa.gov/multimedia/imag...9/N00133497.jpg

Looks like it, nice catch. I wonder if Daphnis' slight inclination is forcing these waves to also have vertical excursions or if it's merely piling up of material somehow forcing it to spread vertically.

I'm not even sure these are the first images showing these shadows. I haven't checked every raw JPG image (far from it) - others here who have done so may know better. The shadows shouldn't just magically appear once the solar elevation angle drops below 2 degrees, they should be visible at higher angles as well - I wouldn't be surprised if they first appeared several months ago.

There probably were hints of the shadows for some time now, but it comes down to the observations executed, distance, etc. Also, these shadows could be a fairly localized phenomenon for all we know, not extending around the entire ring circumference.

In a way, spotting them is similar to Enceladus' geysers - they've been there all along but it took a combination of factors to make them noticeable.

Trawling through recent Daphnis images it looks like some shadows of disturbances were already visible on this image from January 31st:
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00128822.jpg

I don't suppose that's the earliest example either.