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ASTR-3040: Astrobiology

ASTR-3040: Astrobiology. The Habitability of Earth. Day 5. Homework. Due Tue. Feb. 8 Chapter 4: 3, 9, 18 21, 27, 32 37, 42, 46 49, 50, 54. Chapter - 4. Geology & Life Earth is unique within our solar system Moderate Temperatures (slight greenhouse effect) ‏ Abundant water

marcia-stephenson
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ASTR-3040: Astrobiology

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  1. ASTR-3040: Astrobiology The Habitability of Earth Day 5

  2. Homework • Due Tue. Feb. 8 • Chapter 4: • 3, 9, 18 • 21, 27, 32 • 37, 42, 46 • 49, 50, 54

  3. Chapter - 4 • Geology & Life • Earth is unique within our solar system • Moderate Temperatures (slight greenhouse effect)‏ • Abundant water • Protective atmosphere • Relatively stable environment • Contrast Moon, Mercury, Venus, Mars (Fig 4.1)‏ • Distance from Sun • Volcanism & Plate Tectonics • Magnetic field

  4. Mars Mercury Moon Venus

  5. The History of Life on Earth • Geological Record – fossils and rock layers • 3 basic types of rock (Fig 4.2)‏ • Igneous – molten rock that cools and solidifies • Basalt,Granite • Metamorphic – transformed under Pressure/Temperature • Marble, Slate • Sedimentary – gradual compression of sediments • Important to fossil studies – slow buildup with fossils. • Limestone, Sandstone • Rock Cycle (Fig 4.3) + 4.4, 4.5, 4.6

  6. The History of Life on Earth • Rock Analysis • 3 basic types of rock • Mineralogical – identify minerals in the rock • Chemical – determine the elemental composition • Isotopic – ratio of different isotopes - gives formation age • Radioactive Dating (Fig 4.7)‏ • Half-life – probability (Fig 4.8; Table 4.1; Example 4.1)‏ • Parent – Daughter isotopes • Compare with geological record • Sometimes, find organic material (Jurassic Park) (Fig. 4.9)‏

  7. The Geological Time Scale Al26 Mg26 is important for early heating of Earth's core.

  8. The History of Life on Earth • 4 Eons (Fig 4.10)‏ • Hadean - “Hellish” • Archean - “Ancient Life” • Proterozoic - “Earlier Life” • Phanerozoic – Visible Life” • Age of the Earth – oldest rocks 4.0 Gyr • “Zircons” (Fig 4.11) ~4.4 Gyr • Suggest the crust separated from interior ~4.5 Gyrs • Moon rocks ~4.4 Gyr • Therefore, Moon existed by this time.

  9. Hadean Earth, Dawn of Life • 3 generations of atmospheres • Primary – H, He • Planet formation • Secondary – CO2, H2S, SO2, H2O... • Outgassing (Fig 4.12), Comet delivery(?)‏ • Tertiary – N2, O2, H2O • Modified by life

  10. Hadean Earth, Dawn of Life • Late Heavy Bombardment – ~3.9 Gyr ago • Relatively quiet between formation and LHB • Since then, protected by Jupiter • Sterilizing Impacts • 350-400 km in diameter (Fig 4.13)‏ • Completely vaporize the oceans • Global surface temperature rise 2000 C (3600 F)‏ • Last ~4.2-3.8 Gyr ago

  11. Impact Energies and these are the small ones

  12. 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 • Al26 ==> Mg26 contributed a lot of early heat

  13. Geology & Habitatbility • Plate Tectonics (Fig 4.15)‏ • What is it? • What causes it? • Evidence • Continental edge fits (Fig 4.16)‏ • Seafloor spreading • Two types of crust • Seafloor crust – young, high density basalt, thin • Continental crust - old, lower density granite, thick • Figs 4.18 - 4.23

  14. 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)‏ • Figs 4.24 - 4.25

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

  16. Homework • Due Thur. Feb. 10 • Chapter 5: • 4, 6, 14, 20, 25, 27, 33, 37, 42, 47, 48, 49, 51

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