In 1994, a team of scientists led by David Mckay began studying

In 1994, a team of scientists led by David Mckay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984. Two years later, the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars. This evidence includes the discovery of organic molecules in ALH84001, the first ever found in Martian rock. Organic molecules—complex, carbonbased compounds—form the basis for terrestrial life. The organic molecules found in ALH84001 are polycyclic aromatic hydrocarbons, or PAH’s. When microbes die, their organic material often decays into PAH’s.
Skepticism about the McKay team’s claim remains, however. For example, ALH84001 has been on earth for 13,000 years, suggesting to some scientists that its PAH’s might have resulted form terrestrial contamination. However, McKay’s team has demonstrated that the concentration of PAH’s increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination. The skeptic’s strongest argument, however, is that processes unrelated to organic life can easily produce all the evidence found by McKay’s team, including PAH’s. For example, star formation produces PAH’s. Moreover, PAH’s frequently appear in other meteorites, and no one attributes their presence to life processes. Yet McKay’s team notes that the particular combination of PAH’s in ALH84001 is more similar to the combinations produced by decaying organisms than to those originating form nonbiological processes.






I have lots of problems and doubts with the practice questions below… can someone tell me whether my way of thinking is correct or not??



The primary purpose of the passage is to
A. describe new ways of studying the possibility that life once existed on Mars
B. revise a theory regarding the existence of life on Mars in light of new evidence
C. reconcile conflicting viewpoints regarding the possibility that life once existed on Mars
D. evaluate a recently proposed argument concerning the origin of ALH84001
E. describe a controversy concerning the significance of evidence from ALH84001

AjiteshArun
I have doubt in Q1 though I marked it correct
I didn't understand the meaning of option C
I googled the meaning of reconcile it is to make friendly relation but what actually the sentence is trying to mean can you please brief ?
Reconcile has a different meaning here. It means "to show that two seemingly contradictory things are somehow compatible".

Here is a more accurate look at the meaning of reconcile (the first meaning on that page).

"Reconcile conflicting viewpoints regarding X" means "show how conflicting viewpoints about X could be compatible with each other (even though they are "conflicting")".

I just still confused about the explanation above….
For me, I chose option ‘’C’’ at first
However, after reading the article/passage again, I find some clues in paragraph one which I just don’t know whether can offer a more plausible explanation to the correct option E….

the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars…..so only McKay team hold the view that ‘’life once existed on Mars ‘’

Skepticism about the McKay team’s…skeptics focus mainly on ‘’PAH’’, so two side’s argument is mainly focus on “is that processes unrelated/related to organic life (can easily) produce all the evidence found by McKay’s team, including PAH’s.”,not ‘’life once existed on Mars ‘’







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?

(A) ALH84001 may not have originated on Mars.
(B) ALH84001 contains PAHs that are the result of nonbiological processes.
(C) ALH84001 may not have contained PAHs when it landed on Earth.
(D) The organic molecules found in ALH84001 are not PAHs.
(E) The organic molecules found in ALH84001 could not be the result of terrestrial contamination.


Subject: In 1994, a team of scientists led by David McKay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984.
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 13,000 years, which means PAHS might have been because of terrestrial contamination, which are nonbiological processes.
No problem,

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 scienticists

(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).

(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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Sorry,I just cannot quite understand your (GMAT Ninja)"s explanation, and even this question perplex me for quite a long time...

my way of thinking is thus...

since this passage in second paragraph mention this:
ALH84001 has been on earth for 13,000 years, suggesting to some scientists that its PAH’s might have resulted form terrestrial(earth) contamination.--->so ''when''or ''before'' it landed on earth,ALH84001 may not have contained PAHs ...,it is after it landed on earth that ALH84001 start to have contained PAHs...
is my way of thinking correct or not???







The passage suggests that McKay’s team would agree with which of the following regarding the PAHs produced by non organic processes?

(A) These PAHs are not likely to be found in any meteorite that has been on Earth for 13,000 years or more.
(B) These PAHs are not likely to be found in any meteorite that originated from Mars.
(C) These PAHs are not likely to be produced by star formation.
(D) These PAHs are likely to be found in combinations that distinguish them from the PAHs produced by organic processes.
(E) These PAHs are likely to be found in fewer meteorites than the PAHs produced by organic processes.

Please see last sentence of paragraph2
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.

OE #6: It is an inference question McKay’s team notes in { lines 29–34 }that the PAH combinations produced by organic processes can be distinguished from those produced by non organic processes