9.1-9.6 2012-10-30.pdf

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Astronomy & Astrophysics
Michael Reid

Connecting Planetary Interiors and Surfaces Oct 25/12 Reading • Mercury, Venus, earth the moon and mars might have looked the same when they were young ◦ b.c they are made up of rocky material that condensed in the solar nebula • differences among terrestrial planets? ◦ this study is caclled planetary geology What are terrestrial planets like on the inside? • we cant see inside earth or any other planets • we still know about their interiors • for earth most info comes from seismic waves - vibrations that travel both interior and along the surface after an earthquake ◦ this offers clues • all terrestrial worlds have layered interiors • the interior is divided into three layers ◦ 1. Core: highest density material consisting primarily of metals such as nickel and iron. resides in the central core ◦ 2. Mantle: rocky material of moderate density - mostly materials that contain silicon, oxygen and other elements forms the thick mantle ◦ 3. Crust: the lowest density rock, such as granite and basalt (volcanic rock) • earths metallic core consists of 2 distinct regions: a solid inner core and a molten (liquid) outer core • planet's outer layer consists of cool and rigid rock called Lithosphere • lothosphere generally encompasses the crust and part of the mantle • benearth the lithosphere, warmer temp. make the rock softer allow it to deform and to flow much easily • 2 largest terrerstrial planets have thin lithosphere (earth and venus) • a thin lithosphere is brittle and can crack easily • a thick lithoshpere is much stronger ◦ making volcanic eruptions and the formation of mountain ranges What causes geological activity • the surfaces of terrestrial planets can change in time ◦ we use the term geological activity ◦ ex. we say that earth is geologically active b.c volcanic eruptinos, earthquaques erosion and other geological processes reshape the surface How Interiors Get Hot • hot interior contains a lot of thermal energy ◦ and the law of conservation of energy tells us that this energy musy have come from somewhere • sunlight is the primary heat source for terreztrial planets ◦ but they dont effect much ◦ 3 sources of interior heat ‣ 1. Heat of accretion: deposits energy brought in from afar by colliding planetismal ‣ 2. Heat from differentiantion: when a world undergoes differentiation, the sinking of dense material and rising of less - dense materioal means that mass moves inward losing gravitational potential energy ‣ 3. Heat from radioactive decay: the rock and metal that built the terrestrial worlds cotained radioactive isotopes of elements such as uranium, potassium and thorium ◦ 3 Sources of interior cooling: requires tran
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