1. The Moon
Astronomy 311
Professor Lee Carkner
Lecture 13

2. Luna -- The Goddess of the Moon
Since ancient times the Moon has been thought to affect behavior (“lunatic”, “moonstruck”)

3. Viewing the Moon from the Earth
The Moon is the nearest celestial body to the Earth and appears largest in the sky

4. Features of the Moon

5. Principle Features of the Moon
Maria
maria is Latin for seas
Highlands
Craters
range in size from few hundred km to microscopic

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

7. The Moon’s Orbit The Moon is tidally locked
The same side of the Moon always faces the Earth

8. Timeline of Moon Exploration
Luna 1 (USSR, 1959)
Luna 2 (USSR, 1959)
Luna 9 (USSR, 1966)
Luna 10 (USSR, 1966)
Apollo 8 (USA, 1968)
Apollo 11 (USA, 1969)
Luna 16 (USSR), 1970)

9. The Apollo Program
Explored the Moon from 1968 (Apollo 8 orbiter) to 1972 (Apollo 17)

10. Why is the Moon Airless?
The Moon has no atmosphere because its gravitational pull is too weak to keep the molecules from escaping
Moon may have frozen water in the permanent shadows of polar craters

11. The Surface of the Moon Maria: Highlands:
similar to lava on Earth
Highlands:
Entire Moon is also covered in dust from meteor bombardment called regolith

12. Mare Basalt and Anorthosite

13. Cratering and Impacts
The most common feature on the Moon’s surface are craters
Every object in the solar system has been extensively bombarded in the past

14. Heavy Bombardment Period
Early solar system had many small planetesimals and pieces of planetesimals
Happened between 4.6 and 3.8 billion years ago

15. Forming a Crater Impactor hits surface and is vaporized
Middle floor of crater often rebounds (central peak)

16. The Moon’s Interior
Apollo missions left behind seismometers to study moonquakes
Moon once had a magnetic field but does not today, indicating the presence of a small iron core that has solidified

17. Inside The Moon

18. How Did The Moon Form?
What does our formation theory need to explain?

19. Moon Formation Theories

20. Collisional Ejection Theory
Moon was formed when a large (Mars sized) impactor hit the young Earth
The collision put large amounts of debris in orbit, which formed into the Moon

21. Moon Formation Impact

22. Moon Creation Simulation

23. A History of the Moon 4.6 billion years ago:
3 billion years ago-present

24. 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

25. Summary: Surface Maria Highlands
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)