#13 - Concept Reference, Strengthen

[Administrator]

Complete Question Explanation
(See the complete passage discussion here: lsat/viewtopic.php?t=50)

The correct answer choice is (A)

The question stem asks which answer choice gives the most strength to the view that the LHB was limited to the Earth and Moon, consistent with the third theory of LHB, so it would include a relatively brief event that was confined to the Earth-Moon system. The problem with this theory is the Mars rock. How would a scientist explain the rock from Mars if LHB was confined to the Earth-Moon system? Any other evidence of LHB outside the Earth-Moon system would tend to weaken the third theory. Conversely, lack (or disproof) of such evidence would strengthen the theory of confinement to the Earth-Moon system.

Answer choice (A): This is the correct answer choice. If further testing shows that it is unlikely that Mars experienced any increase in projectile intensity of during the LHB (about 4 billion years ago), this would tend to weaken the assertion that Mars was involved, which makes it more likely that the effects of the LHB were not felt beyond the Earth and Moon.

Answer choice (B): Since there doesn’t appear to be much issue with the notion that there was such a bombardment that included both Earth and the Moon, such a discovery would probably do little to alter current hypotheses, and certainly wouldn’t help to disprove any possibility of other planetary bodies being affected by the LHB, so this answer choice is incorrect.

Answer choice (C): As with answer choice (B), this might strengthen the conclusions about the involvement of the Earth and the Moon, but wouldn’t help to disprove the inclusion of other planetary bodies in the phenomenon.

Answer choice (D): Although the Mars rock provides evidence for the assertion that Mars was involved with the LHB, the author cautions that further evidence needs to be gathered before conclusions can be drawn. The discovery of an alternate explanation for the origin of the Mars rock might tend to strengthen a theory that states that LHB is exclusive to the Earth-Moon system, but it would not serve to disprove other theories that are not restricted to the Earth-Moon system, so this answer choice is incorrect.

Answer choice (E): While this evidence would help to explain what was really represented by the LHB (the conclusion of billions of years of heavy bombardment), it would not support the view that the LHB was confined to the Earth and the Moon, so this answer choice is incorrect.

[Sdaoud17]

How come NOt D ? I mean D can support the View LHB was limited to Earth and the Moon ?

PS : can you tell me why the other answer also are incorrect.

[Nikki Siclunov]

You need to support the view that the LHB was a relatively brief event limited to the Earth-Moon system (third theory of LHB). The problem with this theory is the Mars rock: if the event were confined to the Earth-Moon system, how do you explain the rock?

(A) is correct. If additional evidence shows no increase in the intensity of bombardment of Mars during the LHB, this would weaken the assertion that Mars was involved, thus supporting the view that the effects of the LHB were not felt beyond the Earth-Moon system.

(B) is incorrect, because there is no issue with the notion that the bombardment included both Earth and the Moon. The issue is whether the LHB was limited to the Earth-Moon system or not.

(C) is like (B) - both strengthen the notion that the Earth and the Moon were involved, but neither disproves the inclusion of other planetary bodies in the phenomenon.

I agree that (D) is attractive. However, the discovery of an alternate explanation for the origin of the Mars rock would not serve to disprove other theories that are not restricted to the Earth-Moon system. Mars could still have been involved, even if this one particular rock actually originated in the Moon. By comparison (A) essentially disproves the notion that Mars was involved in the LHB, which better supports the theory that the LHB was limited to the Earth-Moon system.

(E) only supports the theory that the LHB occurred, but not that it was confined to the Earth-Moon system.

[Sdaoud17]

thank you

[leahaddad]

I'm a little confused on this one. I ruled out A because theory 2 believed that there was always a high volume bombardment happening, so from my understanding, A could also lend to their theory because even though there wasn't evidence of an INCREASE in heavy bombardment, it could have meant that bombardment stayed at the same rate as it had.

Thus, I chose D because I felt it was strongest.

What did I miss?

[Luke Haqq]

Hi leahaddad!

This question stem asks us to select the answer choice that, "if true, would lend the most support to the view that the LHB was limited to the Earth and the Moon." In other words, we want to find an answer choice that strengthens the particular causal relationship that the LHB impacted only the Earth and Moon but not other planets in the inner solar system:

Cause Effect
LHB surface evidence on the Earth and Moon (only on the Earth and Moon)

Answer choice (A) states, "An extensive survey of craters on Mars shows very little evidence for an increase in the intensity of projectiles striking Mars during the period from three billion to five billion years ago." This strengthens the above causal relationship by buttressing that the cause leads to the particular effect claimed (impacts only on the Earth and the Moon). The passage defines the LHB as a "vigorous bombardment of debris approximately four billion years ago," so if the LHB had affected Mars, then one would expect a change in intensity of projectiles striking it during that period. Even if the intensity of bombardment had stayed the same, this would still suggest that the LHB wasn't a factor.

By contrast, answer choice (D) states, "Based on further testing, scientists conclude that the rock believed to have originated on Mars actually originated on the Moon." Even if this were the case, the passage makes clear (e.g., line 55) that the single rock is hardly conclusive evidence, though it might be suggestive. If the rock were ascertained actually to come from the Moon rather than Mars, this might buttress the view that the LHB indeed impacted the Earth and Moon, but not the view that it impacted only the Earth and Moon but not other bodies in the inner solar system.

[Duval]

Hello!

I chose D because I felt that eliminating the factor of the Mars rock was the strongest approach. However, I do understand why D is not airtight in providing strongest support, but I did not feel A was much stronger. The reason I eliminated A though was because of the phrase "increase in intensity". I didn't see how proving there was no increase in intensity of projectiles means that a rock from Mars couldn't have made it to earth. Existing intensity of projectiles hitting Mars could have already been sufficient to knock debris loose. The passage tells us that rocks from Mars are rare, but there was no part of the passage that indicated this was because projectile intensity was the cause (perhaps the orbits of Mars and Earth rarely line up for debris to hit Earth, perhaps there are so few projectiles hitting Mars that debris itself is rare, etc.). I also don't feel A properly addresses the 'relatively brief duration' that the passage mentions either. I see how A could be the correct answer, but I feel that A has the same issues as D in that it also isn't the strongest supporter, so I guess my question is how to address which is stronger when both are not optimal?

[KelseyWoods]

Hi Duval!

So, yes, the Mars rock lends some support to the idea that Mars was involved in the LHB. But, as the passage says, this was only one rock that might be from Mars and really we would need more rocks before conclusions could be made. Essentially, this one rock merely suggests that it is possible that Mars was involved in the LHB but is not enough by itself to prove or disprove anything. And even being able to determine the rock is in fact from the moon would still not have a big effect because, again, just one rock.

Answer choice (A) provides stronger support for the theory that Mars was not involved in the LHB because it says that Mars doesn't have the kind of craters that would suggest it was part of the LHB. If Mars was part of the LHB, whether or not any Mars rocks made it to Earth, Mars should have the same type of crater evidence to show that it was part of the LHB, like we find on the moon. If there isn't any evidence on the surface of Mars that it was part of the LHB, then the Mars rock becomes pretty irrelevant.

Hope this helps!

Best,
Kelsey

[queenbee]

Hi
I didnt select (A) because Mars is not the only other planet in the solar system. What about Venus? Even if we eliminate mars there are other planets that could be part of LHB. The passage references a potential rock from mars on earth (D). So if we discredit that, we are still just looking at the debris between the moon and earth. Would you please let me know why this logic is wrong? is there some other queue that would indicate there is another reason why (D) is wrong? I am definitely struggling on when we can make think beyond the passage and when we can't.
Thank you!

[Adam Tyson]

It looks like you may have been seeking an answer that would PROVE that the LHB was limited to the Earth and Moon, queenbee, but that's not what we are required to do with a Strengthen question. All we need from the correct answer is some evidence that would support the claim. If the entire inner solar system was involved, then we would expect Mars to have signs of cratering. After all, the whole thing about the Mars rock on Earth is supposed to be evidence that the LHB included some impacts on the surface of Mars, right? So if Mars has no signs of an increase in intense cratering during the time the LHB supposedly happened, that would strongly suggest that Mars was not involved, lending at least some (fairly strong) support to the idea that it was just the Earth and Moon that were affected.

Answer D is very weak, because we already know that the rock in question was not very persuasive. If it wasn't strong evidence that Mars was involved, then taking it away won't be strong evidence that Mars was not involved. Or, put another way, taking that rock out of the equation doesn't tell us that Mars and the rest of the inner solar system were not involved. It just tells us that we don't have any evidence (yet) on Earth to show that it was.

Answer A is a very powerful answer. If something that should be there if the LHB was more widespread is not present, that's a big reason to believe that the LHB was not so widespread.