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

by Nancy Atkinson on April 12, 2009

Saturn ring shadows. Credit: NASA/Cassini

Saturn ring shadows. Credit: NASA/Cassini


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 UnmannedSpaceflight.com 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/UnmannedSpaceflight.com

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


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 UnmannedSpaceflight.com for this amazing find! Great work!

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

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