AST109 Chp 10 (Exam #3) – Flashcards
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anorthosite
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Rock commonly found in ancient, cratered highlands on the Moon
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Capture Theory (of Moon's formation)
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The hypothesis that the Moon was gravitationally captured by Earth
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Center of Mass
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The point between a star and a planet, or between two stars, around which both objects orbit
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Co-create Theory (of Moon's formation)
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The hypothesis that Earth and the Moon formed at the same time from the same material
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Collisional Ejection Theory (of Moon's formation)
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The hypothesis that the Moon formed from material ejected from Earth by the impact of a large asteroid
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Far side (of the Moon)
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The side of the Moon that faces perpetually away from Earth
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Fission Theory (of Moon's formation)
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The hypothesis that the Moon was pulled out of a rapidly rotating proto-Earth
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Impact Breccia
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A type of rock formed from other rocks that were broken apart, mixed, and fused together by a series of meteoritic impacts
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Impact Crater
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A circular depression on a planet or satellite caused by the impact of a meteoroid
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Libration
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An apparent rocking of the Moon whereby an Earth-based observer can, over time, see slightly more than one-half the Moon's surface
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Lunar Highlands
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Ancient, high-elevation, heavily cratered terrain on the Moon
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Mare
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Latin for "sea"; a large, relatively crater-free plain on the Moon
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Mare Basalt
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A type of lunar rock commonly found in the mare basins
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Moonquake
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Sudden, vibratory motion of the Moon's surface
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Regolith
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The layer of rock fragments covering the surface of the Moon
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Synchronous Rotation
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The rotation of a body with a period equal to its orbital period; also called 1-to-1 spin-orbit coupling
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Terminator
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The line dividing day and night on the surface of the Moon or a planet; the line of sunset or sunrise
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Terrae
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Cratered lunar highlands
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Transient Lunar Phenomena
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A flash of light that can occur when meteorites as small as 10 cm hit the lunar surface. Enough heat is generated in the impact to produce light visible from Earth by the naked eye
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Volatile Element
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An element with low melting and boiling points
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T/F: The Moon is less than one Earth-diameter from the Earth.
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False
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T/F: The Moon orbits around the exact center of the Earth.
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False
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T/F: The gravitational force that the Earth feels from the Moon is the same as the gravitational force that the Moon feels from the Earth.
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True
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T/F: The Earth and the Moon form an orbiting system in the same way that the Earth and the Sun form an orbiting system.
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True
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T/F: The Moon's orbit around the Earth is a perfect circle.
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False
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How do the diameters of the Earth and the Moon compare?
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The Earth's is bigger.
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How much of the Moon do we never see from the surface of the Earth?
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About Half
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Put the following lengths in the correct order: the diameter of the Earth, the diameter of the Moon, the distance between the Earth and the Moon.
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Moon diameter, Earth diameter, Earth-Moon distance
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The Moon's diameter is about equal to the distance (along the Earth's surface) between New York City and which other city? (Hint: you can estimate this from your knowledge of geography!)
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Las Vegas, Nevada, USA
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Which of the following characteristics of the Moon is caused by the pull of gravity from the Earth?
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the time the Moon takes to orbit the Earth
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T/F: Astronomers have always agreed on a theory of how the Moon formed.
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False
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T/F: There are many different lines of evidence that can be used to test theories of how the Moon was formed.
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True
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T/F: The collisional ejection theory says that the Moon formed as a result of an object the size of Mars colliding with the Earth.
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True
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T/F: The Moon exploration program was begun for political reasons as well as scientific reasons.
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True
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T/F: Evidence that astronauts really did walk on the Moon can be seen clearly in videos that they took at the time.
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True
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T/F: Only one person (the American astronaut Neil Armstrong) has ever walked on the Moon.
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False
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How did American scientists select the best possible landing sites for human missions to the Moon?
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by photographing most of the Moon's surface from an orbiting robotic spacecraft
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Who sent robotic missions to the Moon?
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the United States, the Soviet Union, Japan, and the European Space Agency
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The average diameter of the Moon is 3476 km and its mass is 7.35 1022 kg. What is its average density (in kg/m3)?
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3344
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The average density of the Moon's surface material is about 2900 kg/m3. Knowing this, what does its overall average density tell you about the amount of iron in the lunar interior compared to Earth's interior?
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Since the Moon's overall average density is only a little larger than its surface density, its interior density must also be just a little larger than its overall density. Thus it must contain little iron, compared to Earth.
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Why do Moonquakes occur more frequently when the Moon is at perigee than at other locations along its orbit?
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At perigee the Moon is closest to Earth, feels the strongest gravitational pull from Earth, and its interior experiences its maximum tidal distortion.
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Why is Earth geologically active whereas the Moon is not?
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Larger bodies retain internal heat energy longer than smaller bodies. Thus Earth has retained more of the internal heat energy from its formation than has the Moon, and this internal heat powers geologic activity. Also, Earth's interior is heated by radioactive decay to a greater extent than the Moon's interior.
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What evidence do we have that the Moon has a more solid interior than does Earth?
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We have done seismic wave studies of the Moon as we have of Earth, and the results suggest a more solid interior for the Moon.
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What evidence do we have that the Moon's interior is not completely solid?
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Our seismic studies have detected Moonquakes, and these require movement that could not happen in a completely solid interior.
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What criticisms can you make of the "cold moon" theory?
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-The denser materials of the maria can only have come from inside the Moon.
-The compositions of the maria and the highlands are not the same.
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What criticisms can you make of the "hot moon" theory?
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The impact breccias are certainly not volcanic.
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How do Earth rocks and Moon rocks compare?
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The Moon rocks contain no water, whereas all Earth rocks contain some water. In addition, Moon rocks are basalt or anorthosite, whereas some Earth rocks are carbonate.
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Rocks found on the Moon are between 3.1 and 4.47 billion years old. By contrast, the majority of Earth's surface is made of oceanic crust that is less than 200 million years old, and the very oldest Earth rocks are about 4 billion years old. If Earth and the Moon are essentially the same age, why is there such a disparity in the ages of the rocks on the two worlds?
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The Moon's surface has been essentially unchanged for billions of years, but Earth's surface is being continually re-formed. The oceanic crust, in particular, is subducted at plate boundaries and replenished at mid-ocean ridges.
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Lunar maria can be formed when
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lava from inside the Moon flows to the surface following a large meteor impact.
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Why do most scientists favor the collisional ejection theory of the Moon's formation?
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Most scientists favor the collision ejection theory because this theory accounts for all the facts, such as the Moon's composition and nearly circular orbit, better and more naturally than do the other theories. A theory that simultaneously solves problems of the similarities and differences between Earth and the Moon is a superior theory.
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Some people who supported the fission theory of lunar formation proposed that the Pacific Ocean basin is the scar left when the Moon pulled away from Earth. Why is this idea probably wrong?
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Because of plate tectonics, the Pacific Ocean basin is a temporary feature on Earth's surface.
