Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Minor Bodies of the Solar System Table of Contents Section 1 Earth’s Moon Section 2 Movements of the Moon Chapter 28

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 Objectives List four kinds of lunar surface features. Describe the three layers of the moon. Summarize the three stages by which the moon formed.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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 to study 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.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lunar Vital Statistics Mean Distance of Moon from Earth – –238,712 mi (384,400 km) Greatest Distance of Moon from Earth (Apogee) - 252,586 mi (406,740 km) Shortest Distance of Moon from Earth (Perigee) - 221,331 mi (356,410 km) Circumference - 6,790 mi. (10,930 km.) –0.27 of Earth's circumference Diameter - 2,160 mi. (3,476 km.) –0.27 of Earth's diameter

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lunar Vital Statistics Mass - 8 x tons (7.35 x kg) Mass Ratio (Earth Moon) Mean Density lb/ft³ (3.34 g/cm³) –0.6 Earth's density Gravity at Surface ft/s² (1.62 m/s²) –1/6 Earth's gravity

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lunar Vital Statistics Orbital Direction –east (counterclockwise) Mean Orbital Speed – –2,287 mi/h (3,683 km/h) Daily Sidereal Motion – ° Synodic Month – – days (29 days, 12 hr. 44 min, 2.8 sec.)

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lunar Vital Statistics Rotational Period - –27 days, 7hr, 43min. 11.5sec Surface Temperature – day = 273 F (120 C) –night = - 244F (-153 C) Estimated Age –4.6 billion years Flight Time from Earth –60 to 70 hours Increase in Mean Distance from Earth –1.5 inches per year (3.8 cm per year)

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 The Lunar Surface mare a large, dark area of basalt on the moon –basalt – dark igneous (volcanic ) rock Any feature of the moon is referred to as lunar. Highlands Light areas are made of anorthosite; a light colored igneous rock Maria - plains of dark, solidified lava ; formed more than 3 billion years ago when lava slowly filled basins that were created by massive asteroids.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Basalt formation on Earth

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 The Lunar Surface Craters, Rilles, and Ridges crater a 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.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Apollo 17, 1972

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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. –Seismometers were left on the moon by astronauts – / /

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Like, Earth, the moon has three compositional layers: the crust, the mantle, and the core.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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 far side than the near sided 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Earth’s Moon Chapter 28 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Movements of the Moon Chapter 28 Objectives Describe the shape of the moon’s orbit around Earth. Explain why eclipses occur. Describe the appearance of four phases of the moon. Explain how the movements of the moon affect tides on Earth.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Movements of the Moon Chapter 28 The Earth-Moon System, continued The Moon’s Elliptical Orbit apogee in the orbit of a satellite, the point at which the satellite is farthest from Earth perigee in 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 28 The Earth-Moon System Section 2 Movements of the Moon

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Movements of the Moon Chapter 28 Eclipses, continued eclipse an 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Movements of the Moon Chapter 28 Eclipses, continued Solar Eclipses solar eclipse the 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Antartica, August 11 solar eclipse; taken from the Mir space station. The two bright spots that appear on the upper left are thought to be Jupiter and Saturn.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Movements of the Moon Chapter 28 Eclipses, continued Lunar Eclipses lunar eclipse the 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu January 15, 2010, Kanyakumari at the southern tip of India.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 28 Phases of the Moon Section 2 Movements of the Moon

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 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.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 28 Causes of Tides Section 2 Movements of the Moon

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