EASC 108 Lecture Notes - Lecture 15: Smog, Appalachian Mountains, Ecliptic
31 Mar 2017
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Document Summary
Most of large & medium sized moons (density > 2g/) probably formed in accretion disks of the planets: all spherical, rotate and revolve in respective ecliptic plane" of each planet in same direction of planets" rotations. Composed of ~50/50 rocky materials & large water ice (no h or he) Small moons have irregular shapes & no orbital pattern; probably captured moons. Terrestrial planets: 75-90% of craters caused by asteroid impact. Few asteroids reach jupiter, virtually none reach saturn: cratering rates should be very low. Jupiter"s gravity partly shields inner solar system from comets: so more cometary impacts in the outer solar system. Jupiter: most impacts come from jupiter family" comets: objects diverted from. Saturn: most impacts come from long-period comets from the oort cloud (1000-100,000 au) Gravity of planet: pull comets inward bigger the planet, the stronger the effect: inner moons of jupiter & saturn have high cratering rates than terrestrial planets while distant moons would have lower rate.
