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Jason DavisAugust 16, 2012

Daphnis cruises through the Keeler Gap

If you've been following Cassini lately, you've probably noticed a lot of rings pictures dominating the raw images. The spacecraft recently left Saturn's equatorial plane for an inclined orbit, which will allow it to capture polar views of the planet and its moons. It will also be making lots of rings observations.

When I see a big series of similar rings images, I'll often download them and splice them together to make a movie. While my results are hardly the stunning productions more experienced videographers have created, it's a fun way to watch the rings rotate, and occasionally you see something interesting happen.

I was doing just that with a set from August 14, and guess who wandered by? Hello, Daphnis! The tiny moon orbits Saturn in the Keeler Gap, which sits near the edge of the A ring. Its gravity tugs on the surrounding ring materials and produces gravitational ripples. I created a little animation to show its motion across Cassini's frame of view. The contrast and brightness have been altered to bring out more detail.

Daphnis cruises through the Keeler Gap

NASA / JPL / Space Science Institute / animation by Jason Davis

Daphnis cruises through the Keeler Gap
Saturn's moon Daphnis cruises through the Keeler Gap in this series of images taken by the Cassini spacecraft. The moon's gravity tugs on the surrounding ring material, creating ripples.

If you aren't terribly impressed with my animation, you're forgiven. But consider this: you're looking at a moon only 8 kilometers wide sitting in a gap of 42 kilometers. And those ripples Daphnis creates are not just horizontal; they have a vertical component as well, ranging up to 1.5 kilometers out of the ring plane. The rings are typically only 10 meters thick. Here's an angled shot Cassini captured in 2009 that shows shadows created by the moon and the ripples:

Daphnis' striking shadows

NASA / JPL / SSI

Daphnis' striking shadows
Saturn's moon Daphnis tugs on surrounding ring materials, casting dramatic shadows across the outer section of the planet's A ring. This image was captured by Cassini in August 2009.

Remember, these images are available to the public! Check out Cassini's raw images section and see for yourself what surprises are waiting to be discovered.

Read more: Cassini, amateur image processing, Saturn's small moons, Saturn

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Jason Davis

Journalist and Digital Editor for The Planetary Society
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