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Moon: A Fascinating Celestial Body

Explore the Moon's temperature, features, exploration timeline, origin theories, surface composition, and energy dynamics in this informative astronomy lecture. Discover intriguing facts about the Moon's history and characteristics.

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Moon: A Fascinating Celestial Body

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  1. The Moon Astronomy 311 Professor Lee Carkner Lecture 13

  2. Temperature of Earth • Temp of Earth from energy balance • TE = [RS/(2 DS)]½ TS • TE = [6.96X108 / (2)(1.496X1011)]½ (5778) • TE = 278.7 K • TF = 1.8TK -460 = (1.8)(278.7)-460 • TF = 41.6 F • Actual Earth temp = 288 K • T = (1.8)(288)-460 = 58.4 F • Earth has an atmosphere, not all of the energy radiated by the Earth gets out

  3. Temperature of Earth • How much energy does Earth emit? • P = sAT4 = s4pRE2T4 • P = (5.67X10-8)(4p)(6.38X106)2(288)4 • P = 1.995X1017 W • What happens if diameter of Earth doubles? • Earth emits more energy • But, Earth also absorbs more energy • T does not depend on Earth size • TE = [RS/(2 DS)]½ TS

  4. Luna -- The Goddess of the Moon • Since ancient times the Moon has been thought to affect behavior (“lunatic”, “moonstruck”) • There is no good evidence for this however

  5. Principle Features of the Moon • Maria • maria is Latin for seas • arrangement of maria produces the “man-in-the-moon” • Highlands • Craters • circular impact structures • range in size from few hundred km to microscopic

  6. Moon Facts • Size: 3476 km diameter • Orbit: 384,000 km • Description: small, airless, cratered • surface is similar to Mercury

  7. Timeline of Moon Exploration • Luna 1 (USSR, 1959) first spacecraft to fly by the Moon • Luna 2 (USSR, 1959) • Luna 9 (USSR, 1966) first lunar lander • Luna 10 (USSR, 1966) • Apollo 8 (USA, 1968) first manned orbiter • Apollo 11 (USA, 1969) • Luna 16 (USSR), 1970) first automated sample return

  8. Near and Far Sides of the Moon

  9. Why is the Moon Airless? • Gravity • Thermal motions • All molecules have a velocity proportional to their temperature • The Moon has no atmosphere because this velocity is too large for its gravity to overcome

  10. The Surface of the Moon • Maria: • covered with dark colored mare basalt • similar to lava on Earth • Highlands: • covered with light colored anorthosite • very old (more than 4 billion years) • Moon rocks are similar in many ways to Earth rocks, but are depleted in volatiles

  11. Mare Basalt and Anorthosite

  12. Tycho and Rays

  13. Falling Bodies • Real impactors get their energy from their very high orbital velocities • A body dropped from a height has potential energy: PE = mgh • 1000 grams = 1 kg • g = 9.8 m/s2 • h is the height above the surface in meters

  14. Energy KE = ½mv2 • Where v is the velocity at impact in meters per second • The kinetic energy at impact must equal the potential energy at the drop point

  15. The Moon’s Interior • Moon is much less active than the Earth • Moon is much less dense than the Earth • Moon once had a magnetic field but does not today, indicating that the core has solidified

  16. Inside The Moon

  17. Moon Formation Theories

  18. Collisional Ejection Theory • The collision put large amounts of debris in orbit, which formed into the Moon • Energy from impact depleted the Moon in volatiles • The ejected material was mostly mantle rock, so the Moon has a very small core

  19. 4.6 billion years ago: 4.6-3.8 billion years ago: ~3.8 billion years ago: large impacts produce mare basins 3.8-3.1 billion years ago: 3 billion years ago-present core solidified, no more magnetic field small amounts of cratering A History of the Moon

  20. Next Time • Read Chapter 10

  21. Summary • Moon was formed 4.6 billion years ago when large impactor hit the Earth • Moon has a low density because it has only a small iron core • Moon has become tidally lock so that only the near-side faces Earth • Most of our information about the Moon comes from the Apollo missions

  22. Summary: Surface • Maria • large impacts produced basins which then filled with lava • darker, denser and younger than the highlands • Highlands • regions that have not experienced large impacts or lava • lighter, less dense and older than the Maria • Large numbers of impacts have covered the surface with craters and regolith (dust)

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