L12GH09_Terrestrial_Planets_I_-_Interior

L12GH09_Terrestrial_Planets_I_-_Interior - February 12,...

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Unformatted text preview: February 12, 2009 planetary interiors Terrestrial Planets I Lecture topics: planetary interiors structure, composition, heating Text Reading: Chapter 8 February 12, 2009 planetary interiors Now to larger SS bodies... Material learned so far can/will be applied to the rest of the SS: planets and satellites What do we know so far?? 9 how to determine distance, physical size 9 radiation both reflected and emitted (BB) 9 composition from reflected light, direct samples, density 9 heating and cooling 9 age, history 9 physical properties vs. orbit, location in SS, other?? February 12, 2009 planetary interiors Interiors some questions How might we learn about the interior structure of the Earth, or other planets? What observations can you make to do this? What calculations can be used? Earth why is the mean density of Earth > the density of crustal rocks? Why is Earths interior hot? Why is Earth hotter than the interiors of other terrestrial bodies? Why do planets have magnetic fields? How do properties of the interior affect planetary surfaces? their atmospheres? What type of data do we have for Earth that we do not have for the other planets? Why? February 12, 2009 planetary interiors Densities A good guess to the composition can be obtained from the mean bulk density Since planetary interiors are under great pressure, the densities are greater than the standard, uncompressed densities of the component elements. Planet bulk unc unc / bulk Mercury 5430kg/m 3 5300kg/m 3 0.976 Venus 5240 4000 0.763 Earth 5520 4100 0.743 Moon 3360 3300 0.982 Mars 3940 3700 0.939 Mercury has the highest content of dense elements (Fe, Mg) Moon and Mars have uncompressed densities similar to various silicates. Low fraction of iron and other metals. February 12, 2009 planetary interiors Densities If we can measure the densities of surface rocks, we can tell something about how differentiated a planet is On small asteroids, the surface rock has density similar to the bulk density. They have a relatively uniform composition. Moon: surface rocks have density of ~2800 kg/m 3 . Indicates the possibility of an iron core Earth surface rocks also have density of ~2800 kg/m 3 . There must be much more iron in the interior....
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This note was uploaded on 04/15/2009 for the course PHYS 275 taught by Professor Harris during the Winter '09 term at Waterloo.

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L12GH09_Terrestrial_Planets_I_-_Interior - February 12,...

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