1. ASTR-1010 Planetary Astronomy Day - 26

3. Announcements Smartworks Chapter 7: Due Friday, March 26. 1 st Quarter Observing Nights: Tues & Thurs, March 23 & 25 -- 7:30pm Lab next week: Rotation Rate of Mercury

4. A Model of the Earth We model the Earth’s interior by studying earthquakes. Sound moves at different speeds through different materials. P (primary) waves travel through solids and liquids. S (secondary) waves go through solids only. Earth’s layers are: crust, mantle, liquid outer core, solid inner core

5. The Earth’s Interior

6. Geology & Habitatbility Earth's Interior – Seismic waves (Fig 4.14)‏  Crust – lowest density, Al, Si, Ca  Mantle – rocky “plastic”  Outer Core – molten  Inner Core – solid, Fe, Ni Earth's Interior – Differentiation  Melting and sedimentation of heavy material to core  Al 26 ==> Mg 26 contributed a lot of early heat

7. The Earth’s Interior Layers: –Crust: continents (low density silicates) and basins (basalt: higher iron content). –Mantle. –Core (iron, nickel and other dense materials). Produced by differentiation in the early Earth: dense materials sink; low-density materials rise.

9. Geology & Habitatbility Plate Tectonics  What is it?  What causes it? Evidence  Continental edge fits  Seafloor spreading  Two types of crust Seafloor crust – young, high density basalt, thin Continental crust - old, lower density granite, thick

10. Earth: Tectonism and Magnetism Laboratory: mid-Atlantic ridge. Plates spreading apart, new material rises in the gap. Solidifying material shows magnetic field at the time. Direction of the field reverses periodically. Rock ages reveal rates of continental drift.

11. Mid-Atlantic Ridge

14. Tectonism Interior heat flows to the surface, producing volcanoes and motion of continental plates. Crustal plates are moved around by convection. Convection = rising and falling of hot/cold material. Motion of interior material also generates magnetic fields. Planet rotation may also be important.

16. Earth’s Magnetic Field

17. Magnetic Field Loss of Atmosphere  Thermal escape – light favored over heavy  Impacts  Solar wind stripping Cause  Electrically conducting interior fluid layer  Convection in the fluid layer  Moderate to fast rotation (dynamo effect)

18. Magnetosphere & Solar Wind Magnetosphere  Protects surface and atmosphere from direct impact  Van Allen Belts Trapped charged particles Directed down to earth at poles