UniverseUniverseEighth EditionEighth Edition

Roger A. Freedman • William J. Kaufmann III

CHAPTER 10CHAPTER 10Our Barren MoonOur Barren Moon

Online quizzes from Chapters 9 Online quizzes from Chapters 9 and 10 due Monday 10/18and 10 due Monday 10/18

Online Quiz from Chapter 11 due Online Quiz from Chapter 11 due Wednesday 10/20Wednesday 10/20

HW Update

Some areas of the Moon are relatively smooth, Some areas of the Moon are relatively smooth, whereas other areas are heavily cratered. This is whereas other areas are heavily cratered. This is because because

A.A. meteors did not strike the flat areas because meteors did not strike the flat areas because they are in the Earth’s shadow. they are in the Earth’s shadow.

B.B. weathering has smoothed parts of the Moon. weathering has smoothed parts of the Moon. C.C. plate tectonics has recycled parts of the lunar plate tectonics has recycled parts of the lunar

crust. crust. D.D. in some places lava flows have covered over in some places lava flows have covered over

older craters, leaving a smoother surface. older craters, leaving a smoother surface. E.E. tidal forces between the Earth and Moon tidal forces between the Earth and Moon

smoothed parts of the Moon. smoothed parts of the Moon.

Q10.4

Some areas of the Moon are relatively smooth, Some areas of the Moon are relatively smooth, whereas other areas are heavily cratered. This is whereas other areas are heavily cratered. This is because because

A.A. meteors did not strike the flat areas because meteors did not strike the flat areas because they are in the Earth’s shadow. they are in the Earth’s shadow.

B.B. weathering has smoothed parts of the Moon. weathering has smoothed parts of the Moon. C.C. plate tectonics has recycled parts of the lunar plate tectonics has recycled parts of the lunar

crust.crust.D.D. in some places lava flows have covered over in some places lava flows have covered over

older craters, leaving a smoother surface.older craters, leaving a smoother surface.E.E. tidal forces between the Earth and Moon tidal forces between the Earth and Moon

smoothed parts of the Moon. smoothed parts of the Moon.

A10.4

The astronaut footprint on the Moon shown in this The astronaut footprint on the Moon shown in this photograph will probablyphotograph will probably

A.A. exist for >10,000 years exist for >10,000 years because there is very little because there is very little weathering on the Moon. weathering on the Moon.

B.B. exist for >10,000 years exist for >10,000 years because the Moon’s surface because the Moon’s surface is hard and durable. is hard and durable.

C.C. exist for <10,000 years due to exist for <10,000 years due to erosion from wind in the erosion from wind in the tenuous lunar atmosphere. tenuous lunar atmosphere.

D.D. exist for <10,000 years due to exist for <10,000 years due to bombardment by large bombardment by large numbers of meteors. numbers of meteors.

E.E. Both C and D are correct.Both C and D are correct.

Q10.1

The astronaut footprint on the Moon shown in this The astronaut footprint on the Moon shown in this photograph will probablyphotograph will probably

A.A. exist for >10,000 years exist for >10,000 years because there is very little because there is very little weathering on the Moon.weathering on the Moon.

B.B. exist for >10,000 years exist for >10,000 years because the Moon’s surface because the Moon’s surface is hard and durable. is hard and durable.

C.C. exist for <10,000 years due to exist for <10,000 years due to erosion from wind in the erosion from wind in the tenuous lunar atmosphere. tenuous lunar atmosphere.

D.D. exist for <10,000 years due to exist for <10,000 years due to bombardment by large bombardment by large numbers of meteors. numbers of meteors.

E.E. Both C and D are correct.Both C and D are correct.

A10.1

Key Ideas Appearance of the Moon:Appearance of the Moon: The Earth-facing side of the The Earth-facing side of the

Moon displays light-colored, heavily cratered highlands Moon displays light-colored, heavily cratered highlands and dark-colored, smooth-surfaced maria. The Moon’s and dark-colored, smooth-surfaced maria. The Moon’s far side has almost no maria.far side has almost no maria.

Virtually all lunar craters were caused by space debris Virtually all lunar craters were caused by space debris striking the surface. There is no evidence of plate striking the surface. There is no evidence of plate tectonic activity on the Moon.tectonic activity on the Moon.

Key Ideas Internal Structure of the Moon:Internal Structure of the Moon: Much of our knowledge Much of our knowledge

about the Moon has come from human exploration in the about the Moon has come from human exploration in the 1960s and early 1970s and from more recent 1960s and early 1970s and from more recent observations by unmanned spacecraft.observations by unmanned spacecraft.

Analysis of seismic waves and other data indicates that Analysis of seismic waves and other data indicates that the Moon has a crust thicker than that of the Earth (and the Moon has a crust thicker than that of the Earth (and thickest on the far side of the Moon), a mantle with a thickest on the far side of the Moon), a mantle with a thickness equal to about 80% of the Moon’s radius, and a thickness equal to about 80% of the Moon’s radius, and a small iron core.small iron core.

Key Ideas The Moon’s lithosphere is far thicker than that of the The Moon’s lithosphere is far thicker than that of the

Earth.Earth. The lunar asthenosphere probably extends from the The lunar asthenosphere probably extends from the

base of the lithosphere to the core.base of the lithosphere to the core. The Moon has no global magnetic field today, although it The Moon has no global magnetic field today, although it

had a weak magnetic field billions of years ago.had a weak magnetic field billions of years ago.

Key Ideas Geologic History of the Moon:Geologic History of the Moon: The anorthositic crust The anorthositic crust

exposed in the highlands was formed between 4.3 and exposed in the highlands was formed between 4.3 and 4.0 billion years ago.4.0 billion years ago.

An era of heavy bombardment formed the maria basins An era of heavy bombardment formed the maria basins between 4.0 and 3.8 billion years ago, and the mare between 4.0 and 3.8 billion years ago, and the mare basalts solidified between 3.8 and 3.1 billion years ago.basalts solidified between 3.8 and 3.1 billion years ago.

The Moon’s surface has undergone very little change The Moon’s surface has undergone very little change over the past 3 billion years.over the past 3 billion years.

Key Ideas Meteoroid impacts have been the only significant Meteoroid impacts have been the only significant

“weathering” agent on the Moon. “weathering” agent on the Moon. The Moon’s regolith, or surface layer of powdered and The Moon’s regolith, or surface layer of powdered and

fractured rock, was formed by meteoritic action.fractured rock, was formed by meteoritic action. All of the lunar rock samples are igneous rocks formed All of the lunar rock samples are igneous rocks formed

largely of minerals found in terrestrial rocks. largely of minerals found in terrestrial rocks. The lunar rocks contain no water and also differ from The lunar rocks contain no water and also differ from

terrestrial rocks in being relatively enriched in the terrestrial rocks in being relatively enriched in the refractory elements and depleted in the volatile refractory elements and depleted in the volatile elements.elements.

Key Ideas Origin of the Moon:Origin of the Moon: The collisional ejection theory of the The collisional ejection theory of the

Moon’s origin holds that the proto-Earth was struck by a Mars-Moon’s origin holds that the proto-Earth was struck by a Mars-sized protoplanet and that debris from this collision coalesced sized protoplanet and that debris from this collision coalesced to form the Moon. This theory successfully explains most to form the Moon. This theory successfully explains most properties of the Moon.properties of the Moon.

The Moon was molten in its early stages, and the anorthositic The Moon was molten in its early stages, and the anorthositic crust solidified from low-density magma that floated to the crust solidified from low-density magma that floated to the lunar surface. The mare basins were created later by the lunar surface. The mare basins were created later by the impact of planetesimals and filled with lava from the lunar impact of planetesimals and filled with lava from the lunar interior.interior.

Tidal interactions between the Earth and Moon are slowing the Tidal interactions between the Earth and Moon are slowing the Earth’s rotation and pushing the Moon away from the Earth.Earth’s rotation and pushing the Moon away from the Earth.