GEOL 212 Lecture Notes - Lecture 53: Tidal Force, Ernest Hemingway, Polar Regions Of Earth
26 Dec 2017
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Density and moment of inertia indicate roughly equal amounts of ice and heavier stuff (silicates and metals). Core: made of iron sulfide and iron. Magnetic surprise: the galileo spacecraft determined that ganymede"s magnetic field is roughly three times that of mercury. It seems to be generated by electrical currents in a europa-style sub- surface ocean of salt water. In ganymede"s case, this ocean is separated from the surface by a thick icy lithosphere. Lithosphere tectonics: we have mentioned the dichotomy of its surface between ancient crater-saturated terrain, and slightly younger grooved terrain reminiscent of europa"s surface. Tectonically, ganymede seems to be a large fossilized version of europa. Ganymede"s wild time is long past and both the ancient dark terrain and the grooved terrain are quite ancient. Compositionally, the smaller icy worlds are like callisto or ganymede - up to one half ice in addition to rock and metals.
