Earth Sciences 1086F/G Lecture Notes - Lecture 6: George Darwin, Terrestrial Planet, Earth'S Rotation
3 Apr 2015
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Mercury has no natural satellite, venus also has none, earth has one (moon), and mars has two puny little misshapen ones. Compared to all other natural planet satellites, moon is unusual: Very large relative to the planet it orbits (earth) Abnormally low density for an object associated with a terrestrial planet. A core that amounts to 2-4% of its total mass, compared to 30% for earth"s core. It is actually very difficult to explain how a planet like earth could be partnered with a satellite like moon, and explaining the origin of moon is a very active area of research today. Prior to the 1970s, three hypotheses were tossed around but there was little hard evidence to support any one. The three suggestions were: moon broke off from a rapidly spinning earth. This was known as the fission hypothesis: earth and moon formed contemporaneously from the same material.
