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PSI's Amanda Hendrix Studies Saturn's Moons

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PSI Senior Scientist Amanda Hendrix is a member of Cassini’s Ultraviolet Imaging Spectrograph science team studying the wide diversity of Saturn’s moons. 
Above, Pan is one of the “UFO” moons of Saturn whose mid-section is cloaked in small, icy grains from the rings. Pan orbits within (and maintains) the Encke gap in Saturn’s A ring. Because Saturn’s gravity is so strong, it is only in a compact region around Pan’s equatorial region that Pan’s own gravity can keep this ring material from drifting away. 
Below, Daphnis is approximately 8 km in diameter and orbits in the Keeler gap (42 km wide) of Saturn’s A ring. Like Pan and Atlas, Daphnis appears to have a narrow ridge around its equator. Though Daphnis is small, its gravitational pull produces waves at the edges of the Keeler gap. The waves are within the plane of the ring and also out of the plane, due to Daphnis’ slight (0.0036°) orbital inclination. Out of the plane, ring particles are attracted toward the moon and then fall back into the ring plane as Daphnis moves away. Within the plane, the waves made by Daphnis in the inner edge of the gap precede it in orbit, while those on the outer edge lag behind it, due to the differences in relative orbital speed. 
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Below, this image shows Epimetheus. The outer edge of the A ring is shepherded and sculpted by resonances with the Janus/Epimetheus coorbitals. Janus and Epimetheus have a "horseshoe" orbital configuration: on average, they orbit at the same distance from Saturn, but at any given time either Epimetheus or Janus may be closer to Saturn; once every 4 years, they switch positions. The new image demonstrates fracture systems or striations on Epimetheus. There appear to be ripples of loose dark material; perhaps fine-grained material slid downhill into the regions between striations.
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June 19, 2017

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