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2. Resources Chapter Presentation Visual Concepts Transparencies Standardized Test Prep Brain Food Video Quiz

3. Chapter 28 Minor Bodies of the Solar System Table of Contents Section 1 Earth’s Moon Section 2Movements of the Moon Section 3Satellites of Other Planets Section 4Asteroids, Comets, and Meteoroids

4. Chapter 28 Section 1 Earth’s Moon Objectives • Listfour kinds of lunar surface features. • Describethe three layers of the moon. • Summarizethe three stages by which the moon formed.

5. Chapter 28 Section 1 Earth’s Moon Exploring the Moon • satellite a natural or artificial body that revolves around planet. • moon a body that revolves around a planet and that has less mass than the planet does. • Seven of the planets in our solar system have natural satellites, or moons. Our moon is Earth’s satellite. • The Apollo space program sent six spacecraft tostudy the moon. Scientists were able to gather data about the moon’s weak gravity and its effect on astronauts, as well as data about the moon’s surface.

6. Chapter 28 Section 1 Earth’s Moon The Lunar Surface marea large, dark area of basalt on the moon • Any feature of the moon is referred to as lunar. • The light patches seen on the moon’s surface are called anorthosites. The darker areas are called maria. • Maria are plains of dark, solidified lava which forme more than 3 billion years ago when lava slowly filled basins that were created by massive asteroids.

7. Chapter 28 Section 1 Earth’s Moon The Lunar Surface Craters, Rilles, and Ridges cratera bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs • The surface of the moon is covered with craters, rilles, and ridges. Most of the craters formed when debris struck the moon about 4 billion years ago. • Rilles are long, deep channels that run through the maria. Rilles are thought to be leftover lava channels from the formation of the maria. • The moon’s surface also has several ridges, which are long, narrow elevations of rock that rise out of the surface and criss-cross the maria.

8. Chapter 28 Section 1 Earth’s Moon Reading check Name two features of the moon.

9. Chapter 28 Section 1 Earth’s Moon Reading check, continued Name two features of the moon. The moon’s features include maria, craters, ridges, and rilles.

10. Chapter 28 Section 1 Earth’s Moon The Lunar Surface, continued Regolith • The moon’s surface is very susceptible to meteorite hits because the moon has no atmosphere for protection. • Over billions of years, these meteorites crushed much of the rock on the moon’s surface into a layer of dust and small fragments called regolith. • The depth of regolith on the moon varies from 1 m to 6 m.

11. Chapter 28 Section 1 Earth’s Moon The Lunar Surface, continued Lunar Rocks • Lunar rocks are igneous, and most rocks near the surface are composed mainly of oxygen and silicon. • Rocks from the lunar highlands are light-colored, coarse-grained anorthosites that contain calcium and aluminum. • Rocks from the maria are fine-grained basalts and contain titanium, magnesium, and iron. • Breccia is found in both maria and the highlands. Lunar breccia formed when meteorites struck the moon.

12. Chapter 28 Section 1 Earth’s Moon The Interior of the Moon • The interior of the moon is less dense than the interior of earth. • Scientists have determined that the moon’s interior is layered by studying seismic information collected during moonquakes. • Like, Earth, the moon has three compositional layers: the crust, the mantle, and the core.

13. Chapter 28 Section 1 Earth’s Moon The Interior of the Moon, continued The Moon’s Crust • The side of the moon that faces Earth is called the near side, while the side of the moon that faces away from Earth is called the far side. • The moon’s crust is thicker on side than the other. • The crust on the near side is about 60 km thick. The crust on the far side is up to 100 km thick. • The difference in thickness was caused by the pull of Earth’s gravity during the formation of the moon.

14. Chapter 28 Section 1 Earth’s Moon Reading check Name two features of the far side of the moon.

15. Chapter 28 Section 1 Earth’s Moon Reading check, continued Name two features of the far side of the moon. The crust of the far side of the moon is thicker than the crust of the near side is. The crust of the far side also consists mainly of mountainous terrain and has only a few small maria.

16. Chapter 28 Section 1 Earth’s Moon The Interior of the Moon, continued The Moon’s Mantle and Core • Beneath the crust is the moon’s mantle. The mantle is thought to be made of rock that is rich in silica, magnesium, and iron. • Scientists think that the moon has a small iron core that has a radius of less than 700 km. • Studies of the core have shown that the moon’s rotation is not uniform and that the core is neither completely solid nor completely liquid.

17. Chapter 28 Section 1 Earth’s Moon The Formation of the Moon The Giant Impact Hypothesis • Most scientists agree that the moon formed in three stages. • The giant impact hypothesis states that the formation of the moon began when a large object collided with Earth more than 4 billion years ago. • The collision ejected chunks of Earth’s mantle into orbit around Earth. The debris eventually clumped together to form the moon. • This hypothesis explains when moon rocks share many of the chemical characteristics of Earth’s mantle.

18. Chapter 28 Section 1 Earth’s Moon The Formation of the Moon, continued Differentiation of the Lunar Interior • Early in its history, the lunar surface was covered by an ocean of molten rock. • Over time, the densest materials moved toward the center of the moon and formed a small core. • The least dense materials formed an outer crust. • The other materials settled between the core and the outer layer to form the moon’s mantle.

19. Chapter 28 Section 1 Earth’s Moon The Formation of the Moon, continued Meteorite Bombardment • When the moon first formed, it was bombarded with meteorites, creating craters and regolith on the moon’s surface. • About 3 billion years ago, less material struck the lunar surface, and few new craters formed. • Craters that have rays formed during the most recent meteor impacts. During this stage, virtually all geologic activity stopped on the moon.

20. Chapter 28 Section 1 Earth’s Moon The Formation of the Moon, continued Lava Flows on the Moon • After impacts on the moon’s surface foremd deep basins, lava flowed out of cracks, or fissures, in the lunar crust. • This lava flooded the crater basins to form maria. • The presence of maria suggest that fissure eruptions once characaterized the moon.

21. Chapter 28 Section 1 Earth’s Moon The Formation of the Moon, continued Lava Flows on the Moon • Because of the uneven thickness of the moon’s crust, more maria formed on the near side of the moon than on the far side. • Scientist do not yet know how magma formed in the lunar interior or how magma reached the surface because there is no evidence of plate tectonics on the moon. • Some scientists think the magma was formed by the large amount of energy that was produced by the long period of intense meteorite bombardment. Other scientists think radioactive decay of materials may have caused magma to form.

22. Chapter 28 Section 1 Earth’s Moon Formation of the Moon

23. Chapter 28 Section 1 Earth’s Moon Formation of the Moon

24. Section 2 Movements of the Moon Chapter 28 Objectives • Describethe shape of the moon’s orbit around Earth. • Explainwhy eclipses occur. • Describethe appearance of four phases of the moon. • Explainhow the movements of the moon affect tides on Earth.

25. Section 2 Movements of the Moon Chapter 28 The Earth-Moon System • Earth and the moon revolve around each other. Together they form a single system that orbits the sun. • The balance point of the Earth-moon system is located within the Earth’s interior, because Earth’s mass is greater than the moon’s mass. • This balance point is called the barycenter. The barycenter follows a smooth orbit around the sun.

26. Section 2 Movements of the Moon Chapter 28 The Earth-Moon System, continued The Moon’s Elliptical Orbit apogeein the orbit of a satellite, the point at which the satellite is farthest from Earth perigeein the orbit of a satellite, the point at which the satellite is closest to Earth • The orbit of the moon around Earth forms an ellipse, the distance between Earth and the moon varies over a month’s time. • When the moon is farthest from Earth, the moon is at apogee. When the moon is closest to Earth, the moon is at perigee.

27. Section 2 Movements of the Moon Chapter 28 The Earth-Moon System

28. Section 2 Movements of the Moon Chapter 28 The Earth-Moon System, continued Moonrise and Moonset • The moon appears to rise and set at Earth’s horizon because of Earth’s rotation on its axis. • The moon rises and sets 50 minutes later each night. This happens because of both Earth’s rotation and the moon’s revolution. • While Earth completes one rotation each day, the moon also moves in its orbit around Earth. It takes 1/29 of Earth’s rotation, or about 50 minutes, for the horizon to catch up to the moon.

29. Section 2 Movements of the Moon Chapter 28 The Earth-Moon System, continued Lunar Rotation • The moon’s revolution around Earth and its rotation on its axis take the same amount of time. • Because the rotation and revolution take the same amount of time, observers on Earth always see the same side of the moon. • The part of the moon illuminated by sunlight changes as the moon orbits Earth.

30. Section 2 Movements of the Moon Chapter 28 Reading check Why are we unable to photograph the far side of the moon from Earth?

31. Section 2 Movements of the Moon Chapter 28 Reading check, continued Why are we unable to photograph the far side of the moon from Earth? The far side of the moon is never visible from Earth, because the moon’s rotation and the moon’s revolution around Earth takes the same amount of time.

32. Section 2 Movements of the Moon Chapter 28 Eclipses, continued eclipsean event in which the shadow of one celestial body falls on another • Bodies orbiting the sun, including Earth and its moon, cast long shadows into space. An eclipse occurs when one body passes through the shadow of another. • Shadows cast by Earth and the moon have two parts: the inner, cone-shaped part of the shadow called the umbra and the outer part of the shadow called the penumbra.

33. Section 2 Movements of the Moon Chapter 28 Eclipses, continued Solar Eclipses solar eclipsethe passing of the moon between Earth and the sun; during a solar eclipse, the shadow of the moon falls on Earth. • During a total solar eclipse, the sun’s light is completely blocked by the moon. The umbra falls on the area of Earth that lies directly in line with the moon and the sun. • Outside the umbra, but within the penumbra, people see a partial solar eclipse. The penumbra falls on the area that immediately surrounds the umbra.

34. Section 2 Movements of the Moon Chapter 28 Eclipses, continued Effects of Solar Eclipses • During a total solar eclipse, the sunlight that is not eclipsed by the moon shows the normally invisible outer layers of the sun’s atmosphere. • This causes what is known as the diamond-ring effect, because the sunlight often glistens like the diamond on a ring. • If the moon is at or near apogee during a solar eclipse, the moon’s umbra does not reach Earth. This causes an “annual eclipse” in which a thin ring of sunlight is visible around the outer edge of the moon. • The brightness of this ring prevents observers from seeing the outer layers of the sun’s atmosphere.

35. Section 2 Movements of the Moon Chapter 28 Reading check What is one difference between a total solar eclipse and an annular eclipse?

36. Section 2 Movements of the Moon Chapter 28 Reading check, continued What is one difference between a total solar eclipse and an annular eclipse? During a total eclipse, the entire disk of the sun is blocked, and the outer layers of the sun become visible. During an annular eclipse, the disk of the sun is never completely blocked out, so the sun is too bright for observers on earth to see the outer layers of the sun’s atmosphere.

37. Section 2 Movements of the Moon Chapter 28 Eclipses, continued Lunar Eclipses lunar eclipsethe passing of the moon through Earth’s shadow at full moon • A lunar eclipse occurs when Earth is positioned between the moon and the sun and when Earth’s shadow crosses the lighted half of the moon. • When only part of the moon passes into Earth’s umbra, a partial lunar eclipse occurs. • When the entire moon passes through Earth’s penumbra, a penumbral eclipse occurs.

38. Section 2 Movements of the Moon Chapter 28 Eclipses, continued Frequency of Solar and Lunar Eclipses • As many as seven eclipses may occur during a calendar year. Four may be lunar, and three may be solar or vise versa. • Total eclipses of the sun and the moon occur infrequently. • Lunar eclipses are visible everywhere on the dark side of Earth. A total solar eclipse, can be seen only by observers in the path of the moon’s shadow as it moves across Earth’s lighted surface. A partial solar eclipse can be seen for thousands of kilometers on either side of the path of the umbra.

39. Section 2 Movements of the Moon Chapter 28 Solar and Lunar Eclipses

40. Section 2 Movements of the Moon Chapter 28 Phases of the Moon phase in astronomy, the change in the illuminated area of one celestial body as seen from another,celestial body; phases of the moon are caused by the changing positions of Earth, the sun, and the moon • As the moon revolves around Earth, different amounts of the near side of the moon, which faces Earth, are lighted. • Therefore, the apparent shape of the visible part of the moon varies.The varying shapes are called phases.

41. Section 2 Movements of the Moon Chapter 28 Phases of the Moon, continued Waxing Phases of the Moon • When the size of the lighted part of the moon is increasing, the moon is said to be waxing. • When a sliver of the moon’s near side is illuminated, the moon enters its waxing-crescent phase. • When a waxing moon becomes a semicircle, the moon enters its first-quarter phase. • When the lighted part of the moon’s near side is larger than a semicircle, the moon is in its waxing-gibbous phase. • At full moon, the entire near side of the moon is illuminated by the light of the sun.

42. Section 2 Movements of the Moon Chapter 28 Phases of the Moon, continued Waning Phases of the Moon • When the lighted part of the near side of the moon appears to decrease in size, the moon is waning. • When the moon is waning, but is still larger than a semicircle, the moon is in the waning-gibbous phase. • When the moon is waning, and it is a semicircle, the moon enters the last-quarter phase. • When only a sliver of the near side is visible, the moon enter the waning-crescent phase. After this phase, the moon becomes a new moon, in which no lighted area of the moon is visible from Earth.

43. Section 2 Movements of the Moon Chapter 28 Phases of the Moon, continued Time from New Moon to New Moon • The moon revolves around Earth in 27.3 days, however, the period from one new moon to the next one is 29.5 days. • This difference of 2.2 days is due to the orbiting of the Earth-moon system around the sun. • In the 27.3 days in which the moon orbits Earth, the two bodies move slightly farther along their orbit around the sun. So, the moon must go a little farther to be directly between Earth and the sun. About 2.2 days are needed for the moon to travel this extra distance.

44. Section 2 Movements of the Moon Chapter 28 Reading check Describe two phases of the waning moon.

45. Section 2 Movements of the Moon Chapter 28 Reading check, continued Describe two phases of the waning moon. When the lighted part of the moon is larger than a semicircle but the visible part of the moon is shrinking, the phase is called waning gibbous. When only a sliver of the near side is visible, the phase is a waning crescent.

46. Section 2 Movements of the Moon Chapter 28 Phases of the Moon

47. Section 2 Movements of the Moon Chapter 28 Lunar Phases

48. Section 2 Movements of the Moon Chapter 28 Tides on Earth • Bulges in Earth’s oceans, called tidal bulges, form because the moon’s gravitational pull on Earth decreases with distance from the moon. • As a result, the ocean on Earth’s near side is pulled toward the moon with the greatest force. • The solid Earth experiences a lesser force. • These differences cause Earth’s tidal bulges. Because Earth rotates, tides occur in a regular rhythm at any given point on Earth’s surface each day.

49. Section 2 Movements of the Moon Chapter 28 Causes of Tides

50. Section 3 Satellites of Other Planets Chapter 28 Objectives • Comparethe characteristics of the two moons of Mars. • Describehow volcanoes were discovered on Io. • Nameone distinguishing characteristic of each of the Galilean moons. • Comparethe characteristics of the rings of Saturn with the rings of the other outer planets.