The Moon's Origin and Characteristics

1. The Moon'sOrigin and Characteristics Arny, 3rd Edition, Chapter 3

2. Motivation • How do you think the Moon was created? Moonset on a clear desert morning Lesson 12: Chap 3, Sec 3.3 and 3.6 The Moon's Motions and Influence on Tides

3. OBJECTIVES • Describe the theories of the Moon’s origins. • Define and summarize the favored theory of the Moon’s origin. • Analyze how the evidence supports the different theories of the Moon’s origin. • What is the Moon’s size and composition? • How does the Moon compare and contrast with the Earth? • What is the Moon’s atmosphere like?

4. VOCABULARY • Debris • Basins • Vaporized • Simulation

5. Earlier Origin Theories • Captured Planet • Twin of Earth, forming side by side • Rapid spinning Earth threw off chunk

6. Favored Theory • Impact of Mars sized planet • Melted and vaporized materials • Left Earth’s core mostly intact • Explains both similarities and differences in composition • Could explain Earth’s tilted axis

7. Creation Steps • Collision • Ejected debris • Molten Moon starts to cool • Small asteroids from collision cause craters that blanket highlands regions • Larger asteroids formed maria basins which flooded with lava

8. Thought Question • What do you think the differences would be on Earth if we had no Moon?

9. Exploration • Apollo Moon landings (1969-1972) • 6 landings, 12 men walked on the Moon • What value was gained?

10. How big is the Moon? • Moon has ¼ the Earth’s diameter and circumference • Moon has 1/10 the Earth’s mass 3,500 km diameter 2,200 mi 6,800 mi circumference 11,000 km 12,800 km or 8,000 mi diameter 40,000 km or 25,000 mi circumference

11. How does the Moon’s composition compare and contrast with the Earth’s? • Moon’s interior is nearly inactive. • What explains this inactivity?

12. How does the Moon’s composition compare and contrast with the Earth’s?(cont’d) • Faster cooling • Less natural radioactive material to supply heat affects motions in interior and on surface

13. How does the Moon’s composition compare and contrast with the Earth’s?(cont’d) • Anything similar? • Core • Mantle • Crust • Anything different? • Symmetry • Liquid regions • Size

14. What are the effects of the Moon’s small size? (cont’d) • Is there a magnetic field? Why? • Is there an atmosphere? • How does its small size affect characteristics? • Are there volcanoes or moonquakes?

15. What are the effects of the Moon’s small size? (cont’d) VERY cold in the shade • No magnetic field • Small size, little iron in the core, lack of liquid core and internal rotation • No plate tectonics • Lack of atmosphere called a vacuum • Extreme temperatures • No volcanic activity to supply gases, plus weak gravity cannot hold gases VERY hot in the sun

16. What does the Moon’s surface look like? • Constant or varying appearance? • What are its major regions? • What other surface features are in these regions? Highlands Maria

17. What does the Moon’ssurface look like? (cont’d) • Major regions: • Highlands – hilly, light-colored regions, heavily cratered • Maria – look like “seas”; dark, congealed lava regions • The Moon has other surface features: • Craters – made by impacts • Rays – shattered rock thrown from crater formation • Rilles - canyons formed from cooling or lava flows • Regolith – fine, powdery soil Craters Rays Rille

18. What does the Moon’s surface look like? (cont’d) • Desolate surface • Unchanged for a long time • No wind, weather, erosion or other forces to change appearance

19. Lesson Review • Define and summarize the favored theory of the Moon’s origin. • How big is the Moon? • ¼ Earth’s diameter and circumference • How does the Moon’s composition compare and contrast with the Earth’s? • Nearly inactive • Not as much iron in core • Differentiated by Earth’s gravity • How did the Moon’s size affect its internal heat? • Faster cooling • Less internal heat ?

20. Lesson Review (cont’d) • Why does the Moon have no magnetic field? • Smaller size, less iron in the core, no liquid core or internal rotation • Why does the Moon have no atmosphere? • No volcanoes, no gases • Weaker gravity

21. Lesson Review (cont’d) • What does the Moon’s surface look like? • Desolate • Two major regions: • Highlands • Maria • Other surface features: • Craters • Rays • Rilles • Regolith

22. Activity—Questions for review • How big is the Moon? • How is the Moon’s interior different from the Earth’s interior? • Why doesn’t the Moon experience plate tectonics? • What are the lunar surface’s two main regions? • What are craters, rays, and rilles? • What is regolith?

23. Activity—Test yourself • The Moon’s diameter is ____ the Earth’s diameter. • The Moon’s surface layer consists of shattered rock chunks and powder from ________ _______. • Some molten material may be below the Moon’s mantle, but its _____ is smaller and contains less iron and nickel than Earth’s. • The Moon doesn’t have a ________ ______ because its core is small, has little iron, and probably doesn’t rotate much. • Because the Earth’s atmosphere is a ___________, the Moon’s surface gets very hot during the day and very cold at night.

24. Activity—Test yourself (cont’d) • The two main regions of the Moon’s surface are ______ and _______. • The __________ on the Moon are bright rugged areas pitted with craters. • The _________ are large, smooth, dark areas on the Moon’s surface. • Circular features on the Moon’s surface with a raised rim caused by meteor impacts are called ___________. • __________ are long, light streaks of pulverized rock radiating away from many craters on the Moon’s surface. • Canyons caused by cracking during cooling and lava flows are called ___________________.

25. Summary • Define and summarize the favored theory of the Moon’s origin. • How does the Moon’s size and composition compare and contrast with the Earth’s? • What effect does this difference have? • What is the Moon’s surface like? • What processes created the surface features?

26. Next • Done—the Moon’s origin and characteristics • Next—the Moon’s motions in space and relationship to ocean tides

27. Arny, 3rd Edition, Chapter 3 QUESTIONS?