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In 1994 a team of scientists led by

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New post 22 Dec 2017, 20:30
Hi all,

Any one can help me explain the answer of question 4. My answer is B, not E (OA). What is wrong in B? Why is E correct?
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New post 28 Dec 2017, 22:50
Can anyone explain me Question - 5.

I was confused between option A and option B.
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New post 31 Dec 2017, 18:07
2
thingocanhnguyen wrote:
Hi all,

Any one can help me explain the answer of question 4. My answer is B, not E (OA). What is wrong in B? Why is E correct?

Quote:
4. The passage suggests that if a meteorite contained PAHs that were the result of terrestrial contamination, then one would expect which of the following to be true?

(A) The meteorite would have been on Earth for more than 13,000 years.
(B) The meteorite would have originated from a source other than Mars.
(C) The PAHs contained in the meteorite would have originated from nonbiological processes.
(D) The meteorite would contain fewer PAHs than most other meteorites contain.
(E) The PAHs contained in the meteorite would be concentrated toward the meteorite’s surface.

Refer to the following sentence: "McKay’s team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination." The word "contrary" suggests that we would expect the opposite to be true if the PAHs were the result of terrestrial contamination. In other words, if the PAHs were the result of terrestrial contamination, the concentration of PAHs would likely DECREASE as one looks deeper into (i.e. moves towards the center of) the meteorite. This matches choice (E).

This makes intuitive sense--imagine a huge ball of rock that lands on Earth with no PAHs. If the rock then becomes contaminated with PAHs while sitting on Earth for thousands of years, we would expect the contamination to affect the surface and then perhaps gradually seep in towards the center.

As for choice (B), if a meteorite contains PAHs that were a result of terrestrial contamination, then we would know nothing of its origin. Maybe it came from Mars, maybe it came from anywhere else in the galaxy. All we would know is that those terrestrial PAHs should not be viewed as evidence of LIFE wherever the meteorite came from. For example, if scientists could PROVE that the PAHs in ALH84001 were a result of terrestrial contamination, this would not change the generally accepted fact that ALH84001 came from Mars. It would simply mean that the PAHs are not evidence of life on Mars.

RMD007 wrote:
Can anyone explain me Question - 5.
Quote:
5. Which of the following best describes the function of the last sentence of the first paragraph?

(A) It identifies a possible organic source for the PAHs found in ALH84001.
(B) It describes a feature of PAHs that is not shared by other types of organic molecules.
(C) It explains how a characteristic common to most meteorites originates.
(D) It suggests how the terrestrial contamination of ALH84001 might have taken place.
(E) It presents evidence that undermines the claim that life once existed on Mars.

I was confused between option A and option B.

The last sentence of the first paragraph is: "When microbes die, their organic material often decays into PAHs." (a microbe is a microorganism).

So if you have microorganisms (i.e. bacteria) that die and decay, you'll often be left with PAHs. The presence of PAHs could be viewed as evidence that life may have existed. Thus, this sentence identifies a possible organic source (e.g. microbes) for the PAHs found in the ALH84001, as stated in choice (A).

As for choice (B), the sentence does not describe a FEATURE of PAHs or how PAHs differ from other types of organic molecules.

I hope that helps!
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New post 14 Jan 2018, 09:34
GMATNinja wrote:
thingocanhnguyen wrote:
Hi all,

Any one can help me explain the answer of question 4. My answer is B, not E (OA). What is wrong in B? Why is E correct?

Quote:
4. The passage suggests that if a meteorite contained PAHs that were the result of terrestrial contamination, then one would expect which of the following to be true?

(A) The meteorite would have been on Earth for more than 13,000 years.
(B) The meteorite would have originated from a source other than Mars.
(C) The PAHs contained in the meteorite would have originated from nonbiological processes.
(D) The meteorite would contain fewer PAHs than most other meteorites contain.
(E) The PAHs contained in the meteorite would be concentrated toward the meteorite’s surface.

Refer to the following sentence: "McKay’s team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination." The word "contrary" suggests that we would expect the opposite to be true if the PAHs were the result of terrestrial contamination. In other words, if the PAHs were the result of terrestrial contamination, the concentration of PAHs would likely DECREASE as one looks deeper into (i.e. moves towards the center of) the meteorite. This matches choice (E).

This makes intuitive sense--imagine a huge ball of rock that lands on Earth with no PAHs. If the rock then becomes contaminated with PAHs while sitting on Earth for thousands of years, we would expect the contamination to affect the surface and then perhaps gradually seep in towards the center.

As for choice (B), if a meteorite contains PAHs that were a result of terrestrial contamination, then we would know nothing of its origin. Maybe it came from Mars, maybe it came from anywhere else in the galaxy. All we would know is that those terrestrial PAHs should not be viewed as evidence of LIFE wherever the meteorite came from. For example, if scientists could PROVE that the PAHs in ALH84001 were a result of terrestrial contamination, this would not change the generally accepted fact that ALH84001 came from Mars. It would simply mean that the PAHs are not evidence of life on Mars.

RMD007 wrote:
Can anyone explain me Question - 5.
Quote:
5. Which of the following best describes the function of the last sentence of the first paragraph?

(A) It identifies a possible organic source for the PAHs found in ALH84001.
(B) It describes a feature of PAHs that is not shared by other types of organic molecules.
(C) It explains how a characteristic common to most meteorites originates.
(D) It suggests how the terrestrial contamination of ALH84001 might have taken place.
(E) It presents evidence that undermines the claim that life once existed on Mars.

I was confused between option A and option B.

The last sentence of the first paragraph is: "When microbes die, their organic material often decays into PAHs." (a microbe is a microorganism).

So if you have microorganisms (i.e. bacteria) that die and decay, you'll often be left with PAHs. The presence of PAHs could be viewed as evidence that life may have existed. Thus, this sentence identifies a possible organic source (e.g. microbes) for the PAHs found in the ALH84001, as stated in choice (A).

As for choice (B), the sentence does not describe a FEATURE of PAHs or how PAHs differ from other types of organic molecules.

I hope that helps!



Hello GMATNinja

i Refered to the following sentence: "McKa y’s team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination." and chose D :-)

if concentration increases than it is from MARS, if contrary ---> if concentration decreasses, that means tha meteorite would contain fewer PAHs than most other meteorites contain ? no :? i was sure about my answer :)
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New post 15 Jan 2018, 07:29
Timing: 7 minutes 14 second.
All correct answers. It seems like LSAT reading practice helps me a lot.
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New post 17 Jan 2018, 18:11
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dave13 wrote:
Hello GMATNinja

i Refered to the following sentence: "McKa y’s team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination." and chose D :-)

if concentration increases than it is from MARS, if contrary ---> if concentration decreasses, that means tha meteorite would contain fewer PAHs than most other meteorites contain ? no :? i was sure about my answer :)

First of all, we do not know that it is from Mars just because concentration of PAHs increases with depth. If the PAHs were the result of terrestrial contamination, the concentration of PAHs would likely DECREASE as one looks deeper into (i.e. moves towards the center of) the meteorite. However, just because this is NOT the case does not necessarily mean the meteorite is from Mars.

Also, how the concentration varies with depth does not tell us anything about the TOTAL amount of PAHs in the meteorite. For example, imagine one meteorite with PAHs from terrestrial contamination and, thus, a higher concentration of PAHs toward the surface. Another meteorite could have PAHs from organic molecules and a higher concentration towards the center. However, the TOTAL number of PAHs in the second meteorite could be less than, equal to, or greater than the total number of PAHs in the first meteorite.

Again, how the concentration varies with depth doesn't tell us anything about the TOTAL number of PAHs. The first meteorite (terrestrial contamination) might have MORE total PAHs than the second (PAHs formed from organic life). Based on the information in the passage, we have no idea whether (D) would be true.

I hope that helps!
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New post 09 Jun 2018, 07:32
GMATNinja wrote:
dave13 wrote:
Hello GMATNinja

i Refered to the following sentence: "McKa y’s team has demonstrated that the concentration of PAHs increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination." and chose D :-)

if concentration increases than it is from MARS, if contrary ---> if concentration decreasses, that means tha meteorite would contain fewer PAHs than most other meteorites contain ? no :? i was sure about my answer :)

First of all, we do not know that it is from Mars just because concentration of PAHs increases with depth. If the PAHs were the result of terrestrial contamination, the concentration of PAHs would likely DECREASE as one looks deeper into (i.e. moves towards the center of) the meteorite. However, just because this is NOT the case does not necessarily mean the meteorite is from Mars.

Also, how the concentration varies with depth does not tell us anything about the TOTAL amount of PAHs in the meteorite. For example, imagine one meteorite with PAHs from terrestrial contamination and, thus, a higher concentration of PAHs toward the surface. Another meteorite could have PAHs from organic molecules and a higher concentration towards the center. However, the TOTAL number of PAHs in the second meteorite could be less than, equal to, or greater than the total number of PAHs in the first meteorite.

Again, how the concentration varies with depth doesn't tell us anything about the TOTAL number of PAHs. The first meteorite (terrestrial contamination) might have MORE total PAHs than the second (PAHs formed from organic life). Based on the information in the passage, we have no idea whether (D) would be true.

I hope that helps!



HI GMAT Ninja,

Could you explain why for question 3, B is wrong? The passage clearly said since this meteorite has been on earth for 13,00 years, which means PAHS might have been because pf terrestial contamination, which are nonbiological processes.
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New post 23 Jun 2018, 08:11
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bondtradercu wrote:
HI GMAT Ninja,

Could you explain why for question 3, B is wrong? The passage clearly said since this meteorite has been on earth for 13,00 years, which means PAHS might have been because pf terrestial contamination, which are nonbiological processes.

No problem, bondtradercu.

Quote:
3. The passage suggests that the fact that ALH84001 has been on Earth for 13,000 years has been used by some scientists to support which of the following
claims about ALH84001?

We need to confirm why scientists are referencing the amount of time that ALH84001 has been on Earth. Let's start with a close look at this part of the passage:

    "...ALH84001 has been on Earth for 13,000 years, suggesting to some scientists that its PAHs might have resulted from terrestrial contamination.
  • terrestrial means "from Earth." In the passage itself, we've read that "Organic molecules...form the basis for terrestrial life."
  • If the PAHs ALH84001 resulted from terrestrial contamination, then these PAHs might not have been present in ALH84001 before it landed on Earth.

Consequently, the correct choice will be a claim suggesting that PAHs were not present in the meteorite until after it landed on Earth. This is directly in line with why the author brings up the number of years ALH84001 has been on Earth and what that fact implies to some scientists.

Quote:
(B) ALH84001 contains PAHs that are the result of nonbiological processes.

This choice is almost the opposite of what we're looking for. If ALHF84001 contains PAHs that result from non biological processes (like star formation), then it would follow that these PAHs were present in ALHF84001 before it landed on Earth. That's why we eliminate (B).

Quote:
(C) ALH84001 may not have contained PAHs when it landed on Earth.

This choice is much more in line with what we've read, which is why it's the best answer choice.
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New post 27 Sep 2018, 22:19
1
1
P1 - a rock found - Martian - organic + PAH
P2 - 2 opposition argument of P1 - evidence to break them.
main point - a theory is given and a debate an a topic is going on.

1. The primary purpose of the passage is to:

(A) describe new ways of studying the possibility that life once existed on Mars - no
(B) revise a theory regarding the existence of life on Mars in light of new evidence - no; this one is little part of the passage.
(C) reconcile conflicting viewpoints regarding the possibility that life once existed on Mars - in part it is true, but those viewpoints were broken later that is not covered.
(D) evaluate a recently proposed argument concerning the origin of ALH84001 - very weak; also not evaluate of this argument.
(E) describe a controversy concerning the significance of evidence from ALH84001 - best of the lot.
-----------------------------------------

2. The passage asserts which of the following about the claim that ALH84001 originated on Mars?
multiple claims made in both p1 and p2.

(A) It was initially proposed by the McKay team of scientists. - no; it was known prior to that.
(B) It is not a matter of widespread scientific dispute. - yes; all accepted that it was from mars. no dispute there.
(C) It has been questioned by some skeptics of the McKay team’s work. - no one did that.
(D) It has been undermined by recent work on PAHs. - no.
(E) It is incompatible with the fact that ALH84001 has been on Earth for 13,000 years. - no.

-----------------------------------------
3. The passage suggests that the fact that ALH84001 has been on Earth for 13,000 years has been used by some scientists to support which of the following claims about ALH84001?
PT - That this rock must have contaminated by now.

(A) ALH84001 may not have originated on Mars. - no
(B) ALH84001 contains PAHs that are the result of nonbiological processes. - no
(C) ALH84001 may not have contained PAHs when it landed on Earth. - yes; should be best of the lot.
(D) The organic molecules found in ALH84001 are not PAHs. - no
(E) The organic molecules found in ALH84001 could not be the result of terrestrial contamination. - yes; but 13000 yes has nothing to do with this fact.

------------------------------------------

4. The passage suggests that if a meteorite contained PAHs that were the result of terrestrial contamination, then one would expect which of the following to be true?
PT - from top to inside, contamination should decrease.

(E) The PAHs contained in the meteorite would be concentrated toward the meteorite’s surface. - yes

-------------------------------------------

5. Which of the following best describes the function of the last sentence of the first paragraph?
last sentence - The organic molecules found in ALH84001 are poly cyclic aromatic hydrocarbons, or PAHs. When microbes die, their organic material often decays into PAHs.

(A) It identifies a possible organic source for the PAHs found in ALH84001. - yes

-------------------------------------------

6. The passage suggests that McKay’s team would agree with which of the following regarding the PAHs produced by non organic processes?
Yet McKay’s team notes that the particular combination of PAHs in ALH84001 is more similar to the combinations produced by decaying organisms than to those originating from non biological processes.

(D) These PAHs are likely to be found in combinations that distinguish them from the PAHs produced by organic processes. - yes
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New post 10 Oct 2018, 04:21
8 Minutes , 35 Seconds , got 5 correct out of 6 . Q4 is a sneaky one !
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