EASC 108 Lecture Notes - Lecture 9: Regolith, Asthenosphere
29 Mar 2017
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Document Summary
Only world visited by humans so far. Earth"s pull slowed rotation of the moon tidally locked: moon"s pull is slowing rotation of earth by ~ 0. 7 sec/year. Earth"s pull also slowing the moon"s orbital velocity: moon is getting further from the earth by 3. 8 cm/year. Composition of moon similar to earth"s mantle but very little metal (iron, nickel) Surface material: regolith : pulverized by constant impacts. ~2500 samples brought back by astronauts; ~800lbs total. All rocks are igneous (i. e. , from molten processes) Moon probably had a weak magnetic field in early history. Solid thin layer just below surface no plate tectonics. Smaller than earth less internal energy, less geological activity. ~30,000 visible with small telescopes, millions visible from orbit origin: interplanetary debris sizes: largest 100s km diam: due to impactors a few km diam large craters often produce central peaks . Impact: meteorite penetrates 2-3 times its own diameter before being stopped and vaporized.
