EASC 108 Lecture Notes - Lecture 14: Shepherd Moons, Roche Limit, Amorphous Carbon
29 Mar 2017
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Document Summary
Rings occur within 2-3 radii away (roche limit: region where gravity of planet so strong that materials cannot stay together to form a moon. Planet"s gravity pulls in material, moons" gravities push and pull in opposite direction. Tug-of-war holds rings in place (for a while: tidal forces near planet prevent small molecules from accreting into larger moons, moonlets are occasionally disrupted by impacts, ongoing small impacts blast off dust and debris to form the rings. Location: within 2-3 radii of saturn (roche tidal zone) Origin: strong tidal force in the roche tidal zone prevents particles from accreting into large object, wandering moon strayed too close to planet and was torn apart by tidal forces. Motions: all particles in the ring orbit the planet according to kepler"s laws. Rings extend from 6,630 to 120,700 km above saturn"s equator. Composed of 93% water ice and 7% amorphous carbon.
