1. Respond to the following: How did the moon get there?
In your notes…
Respond to the following:
How did the moon get there?

2. Capture Theory
Capture- A large object wandered into our early solar system and was captured in the Earth’s gravitational field.
Problems: What could slow the object down enough for the Earth to grab on to it? Why does the Moon have a similar composition?
Both the Earth and the “rogue body” were fully formed
Rogue body wandered into our solar system & was captured by Earth’s gravitational pull
Problem – Earth’s gravitational pull isn’t strong enough to slow a body the size of the moon down enough to capture it into orbit. The moon would have kept on going.
Problem – The moon is made up of the same materials as Earth’s crust and we don’t find that anywhere else in the solar system.

3. Problem – no evidence that the Earth was ever spinning that fast
Fission Theory
That the Earth was spinning so quickly that a bulge formed and was thrown off to form the moon.
Problem – no evidence that the Earth was ever spinning that fast
While Earth was still in a molten state early in it’s formation, it was spinning so fast that a “magma bulge” formed and was flung off into space
This magma bulge eventually cooled and became our moon

4. Co-accretion or Simultaneous Formation
Simultaneous Formation- The Moon and Earth formed at the same time.
Problems: The Earth is iron rich and the Moon isn’t.
The moon is younger than the Earth.
In the area where we are in space, the Earth and moon both formed at the same time and were made of the same materials available in the area
Problem – Earth has a huge iron core compared to the size of Earth. The moon has a very tiny iron core. If they both formed at the same time from the same materials the iron would most likely be more evenly distributed
Problem – Since astronauts brought back moon rocks during the Apollo missions, radio carbon date testing has been done on samples that confirm the moon is younger than the Earth. They did not form at the same time. 5

5. Describe what is happening in this video clip.
The moon
The Big Whack
Describe what is happening in this video clip.
The Big Whack
Describe what is happening in this video clip.
Video clip no longer works, info is still there. 6

6. Most accepted theory today!
Impact Theory
The Impact Theory of the moon’s formation
Earth’s moon formed from a collision between the early Earth and a Mars-sized object
Most accepted theory today!
Earth was a formed body in space
Impactor was Mars-sized
Hit Earth at an off-center angle and almost missed hitting Earth
Impactor was absorbed into Earth’s core and thought to be made of the same materials as Earth
After impact, Earth grew by ~ 25%
Ejected material was thrown outside the Roche Radius and began to orbit Earth
Earth developed a ring system
Moon eventually coalesced from ejected material in orbit

7. Theories for Formation of the Moon
IMPACT THEORY
Video is 6:25
Earth was a formed body in space
Impactor was Mars-sized
Hit Earth at an off-center angle and almost missed hitting Earth
Impactor was absorbed into Earth’s core and thought to be made of the same materials as Earth
After impact, Earth grew by ~ 25%
Ejected material was thrown outside the Roche Radius and began to orbit Earth
Earth developed a ring system
Moon eventually coalesced from ejected material in orbit

8. EVIDENCE Contain similar rocks
Moon rocks lack water – evaporated in space as a result of high temperatures during impact.
Density of the moon is lower that Earth’s ( moon is made of crust and mantle material)
Moon - small iron core

9. OTHER THEORIES
Of Lunar Formation

10. Moonlet Condensation Theory
Earth struck by many comets/asteroids in early solar system formation
Ejected material formed rings around the Earth each time
Rings condensed into moonlets
Moonlets eventually collided/merged with each other
Similar to Impact Theory except that instead of 1 giant impact forming a huge debris ring that coalesced into the moon, many small impacts created small debris rings that coalesced into small moonlets. Over time, these moonlets coalesced into the moon we see today.
Scientists who proposed this theory argue that if a huge Mars-sized object struck Earth, there should be at least some remnants of differing chemical composition among the rocks on Earth and our moon. Where did the pieces from that huge impactor go? (This presumes that Earth and the mars-sized object were not already made of the same materials as an “Earth Twin” planet

11. EVIDENCE Contain similar rocks
Moon rocks lack water – evaporated in space as a result of high temperatures during impact.
Density of the moon is lower that Earth’s ( moon is made of crust and mantel material)
Moon - small iron core
NO evidence of the “Impact Theory” impactor found
Impactors hit Earth at various angles but always appropriate to throw enough debris into space
Ejected material was thrown outside the Roche Radius and began to orbit Earth
Material
Earth developed a ring system
Moonlet formed
Another impact happened and blasted more material beyond the Roche radius
Another moonlet formed
Process repeats forming many moonlets
Moon eventually coalesced from moonlet material in orbit
NOTE: This is a brand new theory. It is still being evaluated at this time so no specific problems with this theory have yet been identified.

12. What are some major observations/noticeable features of the moon?
What do you believe some of these features may be or be caused by?
Maria
Highlands
Maria are dried lava beds left over from early volcanism that existed on the early moon and are at lower elevation than the highlands
Highlands are more heavily cratered than the mare (seas) on the moon and are at higher elevation. They reflect more sunlight and are brighter on the surface
Craters form when objects from space impact on the lunar surface and create a “divot”
Craters

13. So, the same side of the moon is always facing us!
Earth’s Moon
Features
3,475 km (2,150 miles) in diameter (1/4 of Earth’s)
Similar to Earth’s mantle rocks (crust)
Revolution 27 days, 8 hours
Rotation 27 days, 7.2 hours
So, the same side of the moon is always facing us!
Tidally locked

14. Measurement Earth Moon Mean diameter 12,742 km 3,476 km Volume
x 1012 km3
2.199 x 1010 km3
Mass
x 1024 kg
7.349 x 1022 kg
Mean density
5.515
3.342
Surface gravity
9.78 m/s2
1.62 m/s2
Escape velocity
11.2 km/s
2.38 km/s
Visual albedo
0.367
0.12
Visual magnitude
-3.86
+0.21
The Moon has approximately 1/4 Earth's diameter, 1/50 Earth's volume, and 1/80 Earth's mass. Earth is very dense overall (it is the densest planet in the Solar System), but the Moon is light for its size. The difference is partly because Earth has a large core of iron and other heavy metallic elements, while the Moon has only a small core, if it has a core at all. The Moon's surface gravity is 1/6 of Earth's, and escape velocity from the surface is about 1/5 of Earth's.

15. Apollo 15 Feather and Hammer
Apollo 14 Golf
Feather & Hammer video works

16. Locations of Apollo missions
Most are in Maria

17. Cartoon
Create a cartoon of 3 or more frames which depicts the theory of moon formation you most agree with.
Give a written description of what is happening in each slide.
Discuss why you chose this theory of moon formation.