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.
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.
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:
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.