EASC 108 Lecture Notes - Lecture 8: Surface Gravity, Regolith, Basalt
18 Dec 2015
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Document Summary
Earth"s pull slowed rotation of the moon ( tidally locked ) Moon"s pull is slowing rotation of the year by 0. 7 sec/year. Moon is getting farther from the earth by 3. 8 cm/year. Solid layer just below surface no plate tectonics. Smaller than earth so less internal energy, less geological activity. Moon probably had a weak magnetic field early in history. 30,000 craters with telescopes, millions visible from orbit. Due to impactors a few km across. Crater formation: impact : meteorite penetrate 2-3 times it"s own diameter, before being stopped and vaporized. Surface rocks melted and shattered and seismic waves travel through: material vaporized and excavated ( up to several 100 times mass of. Ejecta/debris fall over surrounding area, possibly forming secondary moon impactor ) craters: modifications: Slumping of crater walls to form terraces. Can use cratering patterns to determine relative age of surface. Highlands have many more craters; mare have fewer craters.
