NATS_3-26 - NATS March 26, 2009 Terrestrial Planet Geology...

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NATS March 26, 2009 - Terrestrial Planet Geology and Atmospheres o Why so different? Terrestrial planets all formed out of similar material: rock and metal Their surfaces look very different Why? - A Look Inside o Drills can penetrate about 1% of the Earth’s interior depth o Seismic waves traveling through the Earth can reveal the interior composition o The waves will refract or diffract depending on the type of material (and how much) they encounter as they travel through the Earth o Other planets can be probed less directly (although we do measure seismic waves on the Moon too) o Satellites can also measure the gravitational field of planets at different places, and piece together the density structure that way o Earth: The liquid outer core bends P waves  But stops S waves  - Basic Structure o Core Highest density material, made of heavy metals like Iron, Nickel, Platinum, etc. May be liquid and/or solid. On Earth, the “inner core” is solid, and is surrounded by a liquid “outer core” o Mantle Rocky material surrounding the core, made of minerals like quartz. Because the deep mantle is under pressure and is
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at higher temperature, it is “softer” than layer above it, and can deform and “flow” (similar to glaciers) o Crust Outer layer, made of lower density rocks like granite and basalt o Lithosphere The rigid rock layer that floats on the softer rock beneath. Usually includes the crust and part of the mantle. o Planets like Earth, Venus, Mars have all of these components, but at different ratios - Differentiation o Densest material inside: why? o Piece of iron atop piece of ice: what happens? Nothing would happen. It’s just like stacking blocks. o Liquid iron dropped into liquid water: what happens? Would sink to the bottom o Liquids differentiate: gravity pulls denser material to the bottom (against buoyancy) o Earth and other terrestrial planets must have been hot enough to melt! -
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NATS_3-26 - NATS March 26, 2009 Terrestrial Planet Geology...

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