A9 - Exploring the Moon

Question 1

Describe the Moon’s major internal divisions:

Answer 1

-same layers as Earth (apart from the partial melt region after the outer core), but notable differences:

-crust is much thicker than Earth’s (50km near side, 150km on far side)
-core is <25% of its radius (compared to Earth’s >50%)
-the core is offset by 2km towards its near side

Partial melt isn’t on the diagram, but it is after OC and before mantle

The fact that there are more maria on the near side is clear due to the thinner crust

Question 2

Describe how the near side is different to the far side of the Moon:

Answer 2

-far more maria
-less mountainous terrae (highlands)
-lower albedo (reflectivity)

Question 3

How has data been collected about the far side of the Moon?

Answer 3

-lunar libration (allows 59% of the entire surface to be visible)

-Luna 3
-Apollo 8

Question 4

Describe the Luna 3 mission:

Answer 4

-it was a flyby mission
-the first photo of the Moon’s far side was taken by Luna 3 in 1959

-very hard back then due to communication and camera focus/exposure difficulties

No digital cameras, so the photographic film had to be developed onboard

Question 5

Describe the Apollo 8 mission:

Answer 5

astronauts were flown around the Moon to take photos (including the famous Earthrise photo)

Question 6

Describe how a rocket would have to reach the Moon:

Answer 6

must use a powerful rocket that can produce enough thrust to reach escape velocity (the velocity needed for a body to escape from a gravitational field without undergoing any further acceleration)

Roughly 11.19km/s, or 25,000mph

Question 7

Name 3 hypotheses/theories that describe the formation of the Moon:

Answer 7

-Giant Impact Hypothesis (most popular)

-Capture Theory
-Co-accretion Theory

Question 8

Describe the Giant Impact Hypothesis:

Answer 8

-Earth (as a proto-planet) got hit by another Mars-sized proto-planet (called Theia)
-the ejected matter collected in orbit around Earth to form the Moon

Question 9

Describe the evidence that supports the Giant Impact Hypothesis:

Answer 9

the hypothesis explains the similar composition of the two bodies, and there are minerals on the Moon that can’t be formed unless there are very high temperatures involved (implying a high-energy collision)

Question 10

Describe the Capture Theory:

Answer 10

Moon formed elsewhere in the SS, but came by close enough to be captured by Earth’s gravity

Question 11

Describe the evidence for and against the Capture Theory:

Answer 11

-it is similar to how Mars got its moons

-however, the Moon’s composition would be very different if it were captured, but it is actually very similar

Question 12

Describe the Co-accretion Theory:

Answer 12

Moon formed in the same location from the same deposits of material that accreted around a common centre of gravity

Question 13

Describe the evidence for and against the Co-accretion Theory:

Answer 13

-it may be true since the Moon is tidally locked

-but it would also suggest that they would be made from the same material, but they aren’t exactly the same