What is the Moon Like? Chapter 28.2

The Moon is different than other moons: The Moon is different than other moons: It is large (especially compared to the size of Earth) 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 is more dense (It’s rocky while most moons are rock/ice mixtures It orbits farther from the planet than most moons It orbits farther from the planet than most moons

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 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 The surface is covered in impact craters There are so many craters because there is no erosion on the Moon to erase them. There are so many craters because there is no erosion on the Moon to erase them.

The dark areas are called “mare (pl: maria)” and consist of basalt. The dark areas are called “mare (pl: maria)” and consist of basalt. The light areas are called “highlands.” The light areas are called “highlands.” Analogy: maria are like oceanic crust, highlands are like continental crust. Analogy: maria are like oceanic crust, highlands are like continental crust. The maria are generally smoother and therefore younger than the highlands. The maria are generally smoother and therefore younger than the highlands. Maria form when impact craters fill with lava. Maria form when impact craters fill with lava.

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

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

Simultaneous Formation Theory states that the Moon formed in orbit around the Earth at the same time Earth Formed. Simultaneous Formation Theory states that the Moon formed in orbit around the Earth at the same time Earth Formed. This explains the chemical similarities with Earth. This explains the chemical similarities with Earth. We would expect the same ratio of iron-to- silicates as the Earth but the Moon is much lower in iron. We would expect the same ratio of iron-to- silicates as the Earth but the Moon is much lower in iron.

Impact Theory states that a Mars-sized object collided with Earth early in it’s formation. The material knocked loose formed the moon. Impact Theory states that a Mars-sized object collided with Earth early in it’s formation. The material knocked loose formed the moon. This would explain why the chemical properties of the Moon and Earth are similar 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 explains the relative lack of iron on the Moon (the crust is what was knocked loose) This is the most accepted theory This is the most accepted theory