What is the Moon Like?What is the Moon Like?

Chapter 28.2Chapter 28.2

The Moon is different than other The Moon is different than other moons:moons: It is large (especially compared to the It is large (especially compared to the

size of Earth)size of Earth) It is more dense (It’s rocky while most It is more dense (It’s rocky while most

moons are rock/ice mixturesmoons are rock/ice mixtures It orbits farther from the planet than It orbits farther from the planet than

most moonsmost moons

The Moon is the brightest object in The Moon is the brightest object in the night sky, even though it doesn’t the night sky, even though it doesn’t reflect much light. It’s reflect much light. It’s albedoalbedo is is about 7% (Earth’s is about 31%)about 7% (Earth’s is about 31%)

The surface is covered in impact The surface is covered in impact craterscraters There are so many craters because There are so many craters because

there is no erosion on the Moon to erase there is no erosion on the Moon to erase them.them.

The dark areas are called “mare (pl: The dark areas are called “mare (pl: maria)” and consist of basalt.maria)” and consist of basalt.

The light areas are called “highlands.”The light areas are called “highlands.” Analogy:Analogy: maria are like oceanic crust, maria are like oceanic crust,

highlands are like continental crust.highlands are like continental crust. The maria are generally smoother and The maria are generally smoother and

therefore younger than the highlands.therefore younger than the highlands. Maria form when impact craters fill Maria form when impact craters fill

with lava.with lava.

There are three basic theories of the There are three basic theories of the formation of the moon:formation of the moon: Capture TheoryCapture Theory Simultaneous Formation TheorySimultaneous Formation Theory Impact TheoryImpact Theory

Capture Theory Capture Theory states that the states that the Moon formed somewhere else in the Moon formed somewhere else in the solar system and was captured by solar system and was captured by Earth’s gravity.Earth’s gravity. Other planets have captured moons Other planets have captured moons This theory doesn’t explain why the This theory doesn’t explain why the

Moon and Earth’s chemistry is so similarMoon and Earth’s chemistry is so similar

Simultaneous Formation TheorySimultaneous Formation Theory states that the Moon formed in orbit states that the Moon formed in orbit around the Earth at the same time around the Earth at the same time Earth Formed.Earth Formed. This explains the chemical similarities This explains the chemical similarities

with Earth.with Earth. We would expect the same ratio of iron-We would expect the same ratio of iron-

to-silicates as the Earth but the Moon is to-silicates as the Earth but the Moon is much lower in iron.much lower in iron.

Impact TheoryImpact Theory states that a Mars- states that a Mars-sized object collided with Earth early sized object collided with Earth early in it’s formation. The material in it’s formation. The material knocked loose formed the moon.knocked loose formed the moon. This would explain why the chemical This would explain why the chemical

properties of the Moon and Earth are properties of the Moon and Earth are similarsimilar

This explains the relative lack of iron on This explains the relative lack of iron on the Moon (the crust is what was knocked the Moon (the crust is what was knocked loose)loose)

This is the most accepted theoryThis is the most accepted theory