ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

1. The primary purpose of the passage is to

ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

2.  The passage asserts which of the following about the claim that A1H84001 originated on Mars?

ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

3. The passage suggests that the fact that A1H84001 has been on Earth for 13,000 years has been used by some scientists to support which of the following claims about A1H84001?

ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

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?

ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

5. Which of the following best describes the function of the last sentence of the first paragraph?

ln 1994, a team of scientists led by David McKay began studying the meteorite A1H84001, 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 A1H84001, the first ever found in Martian rock. Organic molecules—complex, carbon-based compounds form the basis for terrestrial life. The organic molecules found in A1H84001 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 13,000 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 A1H84001, contrary to what one would expect from terrestrial contamination. The sceptics’ 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 PAHs. 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 A1H84001 is more similar to the combinations produced by decaying organisms than to those originating from nonbiological processes.

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