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The Terrestrial Planets I

The Terrestrial Planets I. The Earth. Topics. Introduction Earth Density and Mass Structure Crust Tides Atmosphere. Introduction. Terrestrial Planets Small, rocky worlds Mercury Venus Earth Mars Comparative Planetology Helps us understand Weather Earthquakes Climate. Venus.

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The Terrestrial Planets I

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  1. The Terrestrial PlanetsI The Earth

  2. Topics • Introduction • Earth • Density and Mass • Structure • Crust • Tides • Atmosphere

  3. Introduction • Terrestrial Planets • Small, rocky worlds • Mercury • Venus • Earth • Mars • Comparative Planetology • Helps us understand • Weather • Earthquakes • Climate

  4. Venus Earth

  5. Basic Facts about Earth • Radius • About 6400 km • Shape   • Oblate spheroid • Polar radius 21 km shorter • Composition • Mostly made of materials denser than rock. • The average density is 5,520 kg/m3.

  6. Density = Mass / Volume • Mass of Earth • M = 6 x 1024 kg • Radius of Earth • R = 6.4 x 106 m • Volume of Earth • V = 4 p R 3 / 3 • V = 1.1 x 1021 m3

  7. Measuring the Earth’s Mass • In order to compute the Earth’s density we need • The Earth’s radius • The Earth’s mass • To measure the mass we need to consider • Newton’s laws of motion • Newton’s law of gravity

  8. Newton’s 2nd Law and the Law of Gravity m1 Newton’s 2nd Law Acceleration is Force divided by Mass (kg) R m2 Newton’s Law of Gravity

  9. Recap of Basic Units • Acceleration • meters per second per second: m / s2 • Mass • Kilograms: kg • Force = Mass x Acceleration • kg x m / s2 = Newton (N) • Gravitational Constant (G) • Gravity Force = G x mass x mass / distance2 • G has units: N x m2 / kg2

  10. All Objects Fall with Same Acceleration m R M (Earth mass)

  11. Measuring the Earth’s Mass – II • Radius of Earth is measured to be • R = 6.4 x 106 m • Newton’s constant is measured to be • G = 6.7 x 10-11Nm2/kg2 • The acceleration due to gravity at Earth’s surface is measured to be • a = 9.8 m/s2 Re-arrange to get M = 6 x 1024 kg

  12. Structure of Earth • Crust • Solid, thickness: 35-60km; silicates (Oxygen and Silicon compounds). • Mantle • Plastic, thickness: 2800 km; silicates (Oxygen, Silicon, Iron). • Outer Core • Liquid, thickness: 2400 km; metallic (Iron and Nickel) • Inner Core • Solid, thickness: 1200 km; metallic (Iron and Nickel). The density is about 14 g/cm3. Temperature 5000 K.

  13. Structure of Earth – II

  14. Structure of Earth – III • How have we determined the Earth’s structure? • By using seismology: The study of planetary vibrations; that is, studying the way seismic waves travel through the Earth's interior.  • P waves • Compression waves (like sound waves) – the waves oscillate along the direction of motion of the wave. These waves can travel through solids and liquids. • S waves • Transverse waves (like water waves) – the waves oscillate at right angles to the direction of motion. These waves can travel only through solids.

  15. Earth’s Fractured Crust

  16. Continental Drift • Plate Tectonics • In 1924, Albert Wegener proposed that the Earth’s plates are mobile. • Plates • Can collide and form folded mountains • Can sink beneath others • Can split apart and create rift valleys

  17. AST0616.jpg

  18. Fault Lines California Europa

  19. Tides • Gravitational Tides • Caused by the gravitational interaction between the Moon, Sun and the Earth Moon B C A

  20. How Much Sunlight per Second? • In direct sunlight, Earth receives about 1.3KW(1300 Watts) of power from the Sun. • 1 Watt = 1 Joule (of energy) per second • The cross-sectional area of Earth is given by pR2where R is the radius of Earth. • Total wattage = (Watts/unit area) x Area

  21. And the Answer Is… Total = (Watts / unit area) x Area =1300(W/m2) xp R2(m2) =1300(W/m2) x3.14x (6.4 x 106m)2 =1300 x 3.14 x 6.42 x 106x2W =1.67 x 1017W 167 Peta Watts (1015 W)

  22. ..That is.. • A hydrogen bomb releases about 4 x 1015 Joules • Energy received on Earth every second is equivalent to that released by the detonation of about 1.67 x 1017 J/s/ 4 x 1015 J40 H-bombs / s !

  23. The Coriolis Effect • Gustave Gaspard Coriolis (1792-1843) • First to study in detail the effect of planetary rotation on the movement of objects. • The Coriolis effect influences the movement of the atmosphere on rotating planets. 835 km/h 1,674 km/h

  24. Blue Skies and Beautiful Sunsets • Blue Skies • Nitrogen scatters blue light in all directions across the sky, but leaves the redder light largely unaffected • Beautiful Sunsets • When the Sun is low in the sky, and less bright, we see the residual red light that comes straight at us.

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