Transcript Document

What is the Moon Like?
Chapter 28.2
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The Moon is different than other moons:
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It is large (especially compared to the size of
Earth)
It is more dense (It’s rocky while most moons
are rock/ice mixtures
It orbits farther from the planet than most
moons
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The Moon is the brightest object in the
night sky, even though it doesn’t reflect
much light. It’s albedo is about 7%
(Earth’s is about 31%)
The surface is covered in impact craters
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There are so many craters because there is
no erosion on the Moon to erase them.
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The dark areas are called “mare (pl:
maria)” and consist of basalt.
The light areas are called “highlands.”
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Analogy: maria are like oceanic crust,
highlands are like continental crust.
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The maria are generally smoother and
therefore younger than the highlands.
Maria form when impact craters fill with
lava.
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There are three basic theories of the
formation of the moon:
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Capture Theory
Simultaneous Formation Theory
Impact Theory
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Capture Theory states that the Moon
formed somewhere else in the solar
system and was captured by Earth’s
gravity.
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Other planets have captured moons
This theory doesn’t explain why the Moon and
Earth’s chemistry is so similar
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Simultaneous Formation Theory states
that the Moon formed in orbit around the
Earth at the same time Earth Formed.
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This explains the chemical similarities with
Earth.
We would expect the same ratio of iron-tosilicates as the Earth but the Moon is much
lower in iron.
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Impact Theory states that a Mars-sized
object collided with Earth early in it’s
formation. The material knocked loose
formed the moon.
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This would explain why the chemical
properties of the Moon and Earth are similar
This explains the relative lack of iron on the
Moon (the crust is what was knocked loose)
This is the most accepted theory