Self-study
P1
A vigorous debate in astronomy centers on an epoch in planetary history that was first identified by analysis of rock samples obtained in lunar missions. ██████████ ██████████ ████ ███ █████ ███████ ██ ███ ████ ████ ███████ ██ █ ████████ ███████████ ██ ██████ █████████████ ████ ███████ █████ █████████ █████████ ████ █████ ███████████ ██████ ███████████ ████ ████ ███████████ ████ ████████ ███ ████
Phenomenon ·
Late heavy bombardment
4 billion years ago, Moon and Earth were both massively bombarded with projectiles.
P2
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Hypothesis 1 ·
Large asteroid or comet disintegration
Evidence: size of lunar craters is large, suggests a large asteroid or comet broke apart and bombarded inner solar system with debris.
Hypothesis 2 ·
"LHB" is just a part of an even longer period of bombardment
"LHB" is part of a continuous bombardment that lasted billions of years. "LHB" just happened to be last and hence obliterated evidence of earlier impacts.
Hypothesis 3 ·
LHB only affected Earth-Moon system
Contra hypothesis 1 which claims that LHB affected entire inner solar system (Mars, Earth, Venus, and Mercury).
P3
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Evidence Supporting Hypothesis 1 ·
Mars rock found on Earth
Mars rock dates to same time as LHB, suggesting that Mars experienced bombardment too
Conclusion ·
LHB wasn't just an Earth-Moon phenomenon
At least Mars experienced it too.
Further Research ·
To decide between the different hypotheses
Passage Style
Critique or debate
Phenomenon-hypothesis (RC)
10.
The author mentions that the ███
a
support a particular ██████ ██ ███ ██████ ██ ███ ███
The phrase in question is not mentioned in the context of any particular theory about the extent of the LHB. Additionally, all three theories discussed in P2 account for projectiles hitting Earth, so the purpose of this phrase isn’t to support a particular theory.
b
question the lack ██ ███ ████████ █████ ██ █████
The passage does not question the lack of LHB evidence found on Earth, so (B) can’t be the purpose of the phrase. This just isn’t something that the passage tries to do.
c
advocate certain scientific ██████ ███ ███ ███████ ██ ████ ██ █████
P1 only says that life could not have survived until the LHB ended––this is the extent of the discussion of the origins of life on Earth. The passage does not advocate any scientific models for the origins of life, so (C) can’t be the purpose of the phrase in question.
d
provide a reason ███ ██████████ ███ ██████████ ██ ████████ ███ ███
This is the purpose of the phrase. The fact that the projectiles from the bombardment should have struck Earth meant that life couldn’t have survived on Earth until the end of the LHB. This tells us why scientists care about studying the LHB: it has important implications for understanding the history of life on Earth.
e
introduce additional support ███ ███ ██████ ██ ███ ███
This phrase does not occur in the context of evidence for the dating of the LHB. This isn’t the purpose of the phrase in question.