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Planetary Geology

Planetary Geology. Planets Rock!. Goals. What determines why planets look the way they do. What are the 4 main process that affect a planet’s surface. How does planetary interior affect planetary atmospheres?. Why are planets different?. Different planets look different.

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Planetary Geology

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  1. Planetary Geology Planets Rock!

  2. Goals • What determines why planets look the way they do. • What are the 4 main process that affect a planet’s surface. • How does planetary interior affect planetary atmospheres?

  3. Why are planets different? • Different planets look different. • What determines this? • To understand the outside, you must understand the insides.

  4. Concept Test • The cores of the terrestrial worlds are made mostly of metal because ______. • the terrestrial worlds as a whole are made mostly of metal. • the core contained lots of radioactive elements that decayed into metals. • over billions of years, convection gradually brought dense metals downward to the core. • metals sunk to the centers a long time ago when the interiors were molten throughout. • None of the above.

  5. Internal Heat • Why is heat the driver of geological processes? • What is heat? • Think of temperature on an atomic scale. • Where do you expect change?

  6. Accretion • Planets form out of primordial cloud of gas and dust. • Atoms to dust to grains to rocks to asteroids to planetesimals to planets.

  7. Differentiation • Accreted material is all mixed. • Friction generates heat.

  8. Lithosphere – Radius at which rock is too cool to flow by convection.

  9. Concept Test • Given this description of planetary interiors, we expect: • Smaller planets should cool off faster than bigger ones. • Larger planets should have thinner lithospheres than smaller planets. • There should be fewer signs of geological activity on the surfaces of smaller planets compared to larger ones. • All of the above. • None of the above.

  10. How do we know? • How do we know what is really going on inside planets? • Look for signs of surface activity. Has anything changed recently? • Look for magnetic fields around planet. • Fluid core • Convection of fluid • Rapid rotation

  11. Comparative Planetology • 4 main surface altering processes • Cratering (exogenic) • Volcanism (endogenic) • Tectonics (endogenic) • Erosion (endogenic) • In order for endogenic processes to occur, energy must be available. • Small planets (and moons, and asteroids) generally have little internal heat, and, therefore, little endogenic activity. • Exogenic processes affect everything.

  12. Volcanoes

  13. Volcanoes

  14. Tectonics

  15. Plate Tectonics

  16. Erosion

  17. Alluvial Fan

  18. Craters

  19. New Surface vs. Old • Impacts happen over time. • Can date a surface by the number of craters on its surface. Date since last geologic activity. • Pot holes on road: • Many holes = old road. • Few holes = new road • Resurfacing = energy • One or more endogenic processes. • Another clue to insides.

  20. Why is Earth so Different? • Why do we have oceans of water? • Why doe we have an atmosphere with: • so little carbon dioxide? • so much O2 and N2?

  21. Atmosphere Origins • Outgassing • Volcanoes. • CO2 and H2O main gases. • Mt. St. Helens

  22. Concept Test • For which terrestrial planets is the main atmospheric gas one of the two main gases produced by outgassing? • Only Moon & Mercury • All five planets • Only Venus, Earth and Mars • Only Earth • Only Venus and Mars

  23. The Terrestrial Planets

  24. Goldilocks Planet • Delicate balance: Earth is just right. • No oceans without greenhouse gasses. • Without oceans too many greenhouse gasses. • Without oceans no life. • Without life, no ozone. • No ozone, no life. • How does Earth maintain this balance?

  25. Carbon Cycle Tectonics are crucial!

  26. Nature’s Thermostat • Carbon Cycle has negative feedback. • Increasing temperatures lead to feedback that decreases temperatures, etc. • Positive and negative feedbacks have nothing to do with desirability of outcome.

  27. Too Cool Less Rain Less CO2 dissolves in oceans. More CO2 builds up in atmosphere Increased greenhouse Heats Up.

  28. Too Warm More Rain More CO2 dissolves in oceans. Less CO2 builds up in atmosphere Decreased greenhouse Cool Down.

  29. Cycles

  30. Human Input • Affecting CO2 cycle. • Moving C from ground to air at increased rate. • No increase in rate of C from air to ground.

  31. Mars Today

  32. Positive Feedback • Fossil Fuels – Increase CO2 to atmosphere. • Deforestation – decrease CO2 from atmosphere • Increase CO2 – Increase greenhouse effect • Increase temp – Melting glaciers, ice sheets, polar caps • Less ice – lower planetary albedo • Lower albedo – Earth absorbs more light • More absorption – Increasing surface temperatures.

  33. Homework #6 • Due Monday January 30: • Read Bennett Chapter 6. • Do: Chapter 6 Quiz

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