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Juggernaut_86
- Senior | Next Rank: 100 Posts
- Posts: 33
- Joined: Mon Feb 15, 2010 3:40 pm
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 Mc-Kay team announced that ALH84001, which scientists generally agree originated on MArs, contained compelling evidence that life once existed on Mars. The evidence includes the discovery of organic molecules in ALH84001, the first ever found in Martian rock. Organic molecules- complex, carbon-based compounds- form the basis of terrestrial life. The organic molecules found in ALH84001 are polycyclic aromatic hydrocarbons, or PAHs. When microbes die, their organic material often decays into PAHs.
Skepticism about the McKay team's claim remains, however. For example, ALH84001 has been on Earth for 13000 years, suggesting to some scientists that its PAHs might have resulted from terrestrial contamination. However, 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 skeptics' strongest argument however, is that processes unrelated to organic life can easily produce all the evidence found by McKay's team, including PAHs. For example, star formation produces PAH's. Moreover, PAHs frequently appear in other meteorites, and no one attributes their presence to life 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 nonbiological processes.
Ques) The passage asserts which of the following about the claim that ALH84001 originated on Mars?
(A) It was initially proposed by the McKay team of scientists.
(B) It is not a matter of widespread scientific dispute.
(C) It has been questioned by some skeptics of the McKay team's work.
(D) It has been undermined by recent work on PAHs.
(E) It is compatible with the fact that ALH84001 has been on Earth for 13000 years.
OA after some thoughts....please..
Thanks!
Skepticism about the McKay team's claim remains, however. For example, ALH84001 has been on Earth for 13000 years, suggesting to some scientists that its PAHs might have resulted from terrestrial contamination. However, 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 skeptics' strongest argument however, is that processes unrelated to organic life can easily produce all the evidence found by McKay's team, including PAHs. For example, star formation produces PAH's. Moreover, PAHs frequently appear in other meteorites, and no one attributes their presence to life 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 nonbiological processes.
Ques) The passage asserts which of the following about the claim that ALH84001 originated on Mars?
(A) It was initially proposed by the McKay team of scientists.
(B) It is not a matter of widespread scientific dispute.
(C) It has been questioned by some skeptics of the McKay team's work.
(D) It has been undermined by recent work on PAHs.
(E) It is compatible with the fact that ALH84001 has been on Earth for 13000 years.
OA after some thoughts....please..
Thanks!
