Cassini’s Indirect Image of Boulders and Moonlets in Saturn’s Rings

Take a look at this — it is absolutely stunning. A couple of weeks ago, Anne wrote an article about moon shadows on Saturns rings. Because Saturn is approaching its equinox, in August the rings will “disappear” from our view from Earth, as the rings will be exactly edge-on. But as the rings ease into alignment with the sun, Saturn’s moons cast their shadows across the rings, growing longer as equinox approaches. See in the image above, a shadow is cast on the rings, likely by either the moon Mimas or Tethys. But the eagle-eyed folks over at also noticed something else in this raw image from the Cassini spacecraft. Notice the area right near the middle of the image where the rings look kind of fuzzy? That’s not just camera blur; those are more shadows, created by thousands of boulders or moonlets in the ring! Amazing! We’ve never actually seen the small objects that make up the rings — and we still haven’t — but we’re seeing the shadows they are creating! Let’s zoom in for a closer look:

Shadows on the rings, closer. Credit: NASA/Cassini/
Shadows on the rings, closer. Credit: NASA/Cassini/

Wow! As one of the members of UnmannedSpaceflight said, “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.” Let’s zoom in a little more:
Saturn's rings closer yet. Credit: NASA/Cassini
Saturn's rings closer yet. Credit: NASA/Cassini

The UnmannedSpaceflight crew has even created animations from combining several of the raw images sent back by Cassini. In the first movie, it doesn’t look like the moonlet shadows are moving at all, but in a more zoomed in version, it is obvious the shadows are moving as the objects orbit around Saturn. As Stuart Atkinson at Cumbrian Sky said, for a long time we’ve speculated that Saturn’s rings would look a bit like this, close up:
Artist concept of Saturn's rings. Image courtesy NASA/JPL/University of Colorado
Artist concept of Saturn's rings. Image courtesy NASA/JPL/University of Colorado

And now we have the first image of the ring objects, or at least the shadows they create.

Head nod to Stuart Atkinson for the tip, and congrats to the sharp eyes (and image editing prowess) at for this amazing find! Great work!

23 Replies to “Cassini’s Indirect Image of Boulders and Moonlets in Saturn’s Rings”

  1. Very cool!

    So, we are looking at a very narrow band of tightly packed rocks on the outer edge of the dense ring, I guess…. not quite like the aertist’s conjecture, which depicts the whole ring as rocks… which is what I imgined until recently what it would look like.

  2. This is MAGIC!

    Most grateful to all who are responsible for bringing it together on Earth!

  3. Absolutely astonishing. For years I’ve been lamenting the fact that, for all the amazing detail we’ve seen in the rings, we’ve never really resolved individual boulders or piles of rubble. These images make me feel a LOT better!

    The wonders I have seen in my life …

  4. Eventually, it will be discovered that Hydrogen Metal, migrated from the compressive core area of Saturn to the rings, and the most common crystalline metal in the Universe is what is being viewed, in part.

    It’s a room temperature superconductor, not found on earth, or crust planets, that will be “mined”, so to speak in the future.

    It has phenomenal properties, as yet undreamed of, by present day science.


  5. so the ring section the bright ring is casting shadows onto will be thinner than the bright ring?, and the “rocks” are not breaking each other down into fine dust as was theorised for the rest of the rings formation…or if they are then the bright ring is not very old (destroyed moonlet?)

  6. Wow, this great stuff. It’s almost like reading a graph: long shadows = large boulders, small shadows = small boulders.

    I love astronomy.

  7. It´s the largest vinyl record ever! I wonder what those modulations will sound like! I suspect it´s all small rocks packed up radially with gaps and longitudinally with aggregate clumps

  8. Indeed, GREAT PHOTOS and ARTIST RENDERING. But, you carbon copies should go there soon to see it close-up.
    Saturn’s a unique and beautiful planet, and equally special are the big moons.

  9. Err… Nancy, I’m also eagle-eyed…

    Take a look at this — its absolutely stunning.

    … but in a more zoomed in version, its obvious the shadows are…

    In both cases, it should be it’s, as in it is; not “its”. 🙂

  10. Hmm.! Makes one wonder now about Saturn’s ‘rings of rocks and boulders.’ Maybe we are witness to some super-slow accretion of ring material into a new moon of Saturn. Hey! Who knows! Planetary rings might be one of several precursors to moon formations.

  11. Looks like the show is about to begin. Cassini is about to proceed with a 4 month imaging campaign centered around the August 11th ring crossing. The Rings Equinox campaign (as it’s officially named) will focus on high-res imaging of the ring system, looking for embedded moons, moonlets or even individual ring particles (which they might have found, given the article & relevant images). Some details of the Ring Equinox campaign can be found here: . Hats off to Nancy, and Stu Atkinson for bringing this story to light. On a related note, while perusing the computerized ‘artist concept” of Saturn’s rings, I thought of those hardy space artists rendering this scene WITHOUT the direct aid of a computer.( for the record, I see computers as another tool in the artist’s toolkit. Some of my favorite images are completely digital. Space art evolves!). This makes me appreciate all-the-more paintings of Saturn’s ring system by Don Dixon, Ludek Pesek and others for whom this must have been a time consuming, tedious, pointillistic avenue to create these paintings. BTW, I also know that major ground observatories and Hubble have time allocated around the ring crossing date of August 11 to hunt for embedded moons and moonlets. Can’t wait!

  12. Prime:

    It also dissolves into normal hydrogen when again under normal pressure…

  13. Boring.

    WTF is going on??? You are all acting like we’ve just discovered another Earth.

  14. well, they haven`t discovered another Earth, what they have discovered is thousands of rocks casting a shadow onto the inner rings of Saturn, which opens up a huge barrel of questions and brings some common theories into question, it might be boring to some people, but its probably a pivotal discovery about the structure of the rings around Saturn.

    its boring in the same way that a pile of graphite in a tennis court is, just don`t go to Hiroshima for your holidays

  15. Sorry, but if you think that seeing bizarre new structures and details inside the most glorious system of rings in our solar system, in this, the International Year of Astronomy, is “boring” then you’re in the wrong place.

    One day, maybe in a generation’s time, maybe in a few centuries, manned ships will travel to Saturn, glide silently over the rings, and the passengers crowded at their windows will look down and see an incredible view of shadows being cast across the rings by the largest particles within them… and they’ll know that those shadows were first spotted waaaaay back in 2009, on black and white photographs taken by an unmanned spaceprobe called Cassini. Doesn’t that make the hairs on the back of your neck stand up?

    Every time we find something like this, every time we see something new, every time we receive new images from a probe orbiting another world we’re literally witnessing history being made. That’s why stories like this are so fascinating and so exciting.

  16. There is nothing bizzare about bunch of rocks casting a shadow. Also, the detail is pretty shitty (lol at camera blur). The latest videos (made from pics) from Mars were pretty cool but this???

    Hahaha, you are insane. What the hell are you talking about? Just getting into outer space would be pretty amazing for anybody, but it has nothing to do with shitty shadows on Saturn’s rings.

    You guys should re-evaluate what’s amazing and what’s not.

  17. Thanks Stu for that excellent description of a future tour over Saturn’s rings. For some here on earth only the awe brought by extraterrestrial contact, or discovery of an earth-like planet will generate excitement. However, for the rest of us – even the modest indirect detection of boulders tumbling around our beloved ringed giant fires our imagination and gives cause for celebration.

  18. HeadAroundU:

    […] Hahaha, you are insane. What the hell are you talking about? Just getting into outer space would be pretty amazing for anybody, but it has nothing to do with shitty shadows on Saturn’s rings. […]

    Obviously, HeadAroundU must have his head where the Sun doesn’t shine!


  19. Can anyone define the point at which a boulder becomes a moonlet? I have read of some pretty small objects being called moonlets.

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