Reading comp PrepTest 132 · Section 3 · Question 9

Topic: Science

Paragraph 1

• Paragraph note
  • A phenomenon and why it’s important
• Views, minor Meta-Structures, and the author's attitude
  • Phenomenon - Craters on Moon hint at Late Heavy Bombardment (LHB) 4b years ago - Should have struck Earth, too
  • Importants - Life couldn’t survive until it was over

Paragraph 2

• Paragraph note
  • Three theories about the LHB are stated
• Views, minor Meta-Structures, and the author's attitude
  • Theory 1 - Large body broke up and hit inner solar system
  • Theory 2 - LHB was really billions of years of debris hitting inner solar system
  • Theory 3 - Large body in Earth/Moon broke up and hit those bodies

Paragraph 3

• Paragraph note
  • New evidence supporting a theory
• Views, minor Meta-Structures, and the author's attitude
  • New evidence - Rock on Earth might be from Mars, from around 4b years ago
  • Explanation - Bombardment through inner solar system dislodged rock and sent to Earth
  • Further studies needed for confirmation

Main Point: Though there are many theoretical approaches that explain the Moon’s craters and the LHB (how long it lasted; what astronomical bodies it hit), new evidence suggests that the LHB happened throughout the inner solar system, though more research is needed before that conclusion can be drawn with certainty.

Lines 4-7 - The phenomenon

Line 17 - Theory 1 introduced

Line 21 - Theory 2 introduced

Line 31 - Theory 3 introduced

Lines 40-44 - New evidence introduced

Lines 51-53 - Implications of the new evidence

Lines 53-57 - More studies needed

Phenomenon/Explanation - This passage falls into a common Meta-Structure for Science passages - the Phenomenon/Explanation structure. In this structure, a phenomenon is noted, and explanations - usually causal - are noted. The Author’s preferred explanation tends to serve as the main point. Here, the Phenomenon is described in Paragraph 1, and three approaches are described in Paragraph 2. The Author then presents new evidence in Paragraph 3 that lines up with two of the theories (see our discussion in the Last Thoughts? section), though she’s not fully committed to that view (Lines 53-57). So the main point is a little muddled here, as the Author’s explanation is partial (it addresses the scope of the LHB but not the time period - again, see the discussion in Last Thoughts?) and she thinks more studies are needed to reach the conclusion. This is all reflected in our main point, as written out above.

This is a tough passage because of Paragraph 2, where three theories are outlined. If you didn’t think about how those theories overlap, and how they relate to Paragraph 3, the questions would be exceptionally difficult, so let’s talk about that now.

Looking at the three theories, while they are multifaceted, there are two elements that each speaks to - the time period of the “LHB,” and how widespread it was:

• Theory 1 - It was a short time period when a single body broke apart, and it hit the entire inner solar system
• Theory 2 - It was a long time period (billions of years), and it hit the entire inner solar system
• Theory 3 - It was a short time period when a single body broke apart, and it was limited to the Earth and Moon

Note that each theory has something in common with each other theory!

Now, how does this relate to Paragraph 3? The evidence there supports the view that Mars was hit during the LHB, which suggests that the strikes spread throughout the inner solar system. This supports both Theories 1 and 2 while arguing against Theory 3. Without this view into how the theories relate and how the new evidence overlaps with them, you’d be in trouble for the questions!