1. Ch. 27 Sec. 2 The Moon

2. The Moon, Earth’s nearest neighbor in space, is unique among the moons in our solar system. Review Vocabulary lava: magma that flows onto the surface from the interior of an astronomical body

3. Astronomers have learned much about the Moon from observations with telescopes. However, most knowledge of the Moon comes from explorations by space probes and from landings by astronauts.

4. I. Exploring the Moon • 1957 1. First artificial satellite 2. Sputnik I (Soviet Union) 3. Yuri A. Gagarin a. First human in space b. 1961

5. B. United States 1. Project Mercury a. Alan B. Shepard, Jr 2. Project Gemini a. two-person crews

6. C. July 20, 1969 1. Apollo program (Apollo 11 mission) 2. Neil Armstrong and Edwin “Buzz” Aldrin After a gap of many years, scientists hope to return to the Moon before 2029

7. II. The Lunar Surface • Albedo 1. Reflected light from lunar surface (7%) a. Earth - average albedo of nearly 31% 2. Absorbed light heats surface a. 400K (127oC or 261oF) b. 100K (-173oC or -279oF)

8. B. “Man in the Moon” – produced by surface features • Lunar highlands a. Heavily cratered b. Light in color c. Mountainous

9. 2. Maria Dark in color Smooth plains (few craters) c. Rilles – valleylike structures meandering through maria (might be collapsed lava tubes)

10. C. Lunar craters Impact craters Returning material – ejecta a. Rays - trails of ejecta b. Radiate outward from impact

11. D. Lunar properties 1. Earth’s moon is unique among all the moons in the solar system. It is one of the largest moons compared to the radius and mass of the planet it orbits. It is a solid, rocky body, in contrast with the icy compositions of other moons of the solar system. The Moon’s orbit is farther from Earth relative to the distance of most moons from the planets they orbit.

12. 2. Composition – mostly silicates Highlands: lunar breccias i. fusion of smaller rocks during impacts ii. Plagioclase feldspar b. Maria: predominantly basalt with no water

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14. III. History of the Moon • 3.8 to 4.6 by (about the same age as Earth) • Heavily bombarded during first 800 my • Regolith: ground-up rock on lunar surface

15. Layered structure – inferred from seismic data Crust upper mantle – solid lower mantle - partlially molten Core – solid Fe

16. B. Formation of maria Lava filled in the large impact basins Younger than highlands (3.1 – 3.8 bya) Flowing lava filled rilles

17. C. Tectonics Although there is an annual moonquake of small magnitude, scientists think that the Moon is not tectonically active because the Moon has no active volcanoes and no significant magnetic field.

18. IV. Formation A. Impact 1. Large body (Mars sized) 2. 4.6 bya

19. B. Ejection • Earth mantle material • Impacting body material • Revolution began

20. 3. Formation • Cooling • More impacts • Lava formed maria

23. The Moon, Earth’s nearest neighbor in space, is unique among the moons in our solar system. • Astronomers have gathered information about the Moon using telescopes, space probes, and astronaut exploration. • Like Earth’s crust, the Moon’s crust is composed mostly of silicates.

24. Surface features on the Moon include highlands, maria, ejecta, rays, and rilles. It is heavily cratered. • The Moon probably formed about 4.5 bya in a collision between Earth and a Mars-size object.