Official Explanation
1. The passage is primarily concerned with which of the following?
Difficulty Level: 600
Explanation
(A) There is no widely accepted theory, just speculation. Plus, that speculation is more positive than negative! (Out of scope)
(B) The passage does discuss a potential theory (that there may once have been life on Mars), but the passage itself does not initiate any debate. Rather, it reports on various findings and opinions of others. (Out of scope)
(C) The earliest mentioned interest in Mars was in the mid-seventeenth century; this is not recent. (One word off)
(D) CORRECT.The passage does describe various discoveries made in the mid-seventeenth and mid-nineteenth centuries, as well as more recently, concerning the possibility of life on Mars.
(E) The passage does discuss this, but the rovers are passage detail; they are not the overall point of the passage. (True but not right)
2. Each of the following discoveries is mentioned in the passage EXCEPT
Difficulty Level: 700
Explanation
The question indicates that four of the answers are mentioned in the passage, so this is a detail EXCEPT question. The entire passage is about discoveries, so go straight to the first answer choice and try to find it in the passage.
(A) CORRECT. The passage says only that wind erosion or carbon dioxide may be responsible for certain geological landforms, not that they are. This is an unusual form of an Extreme answer: though the word are is not an extreme word itself, it is more extreme than may. (Extreme)
(B) True. The first paragraph says that Mars no longer possessed a global magnetic field.
(C) True. The second paragraph says that Mars rovers Opportunity and Spirit…discovered geological evidence of past water activity.
(D) True. The first paragraph states that scientists discovered similarities to Earth, including the length of day.
(E) True. The first paragraph states that scientists discovered similarities to Earth, including the… axial tilt.
3. The passage suggests which of the following about polar ice caps?
Difficulty Level: 500
Explanation
The word suggests points to an inference question. The passage mentions polar ice caps in the first paragraph:
As early as the mid-seventeenth century, astronomers observed polar ice caps on Mars, and by the mid-nineteenth century, scientists discovered other similarities to Earth, including the length of day and axial tilt.
The second half of the sentence states that scientists discovered other similarities to Earth, implying that polar ice caps are also a similarity between the two planets.
(A) The passage does mention carbon dioxide, but not in the context of polar ice caps. (Mix-up)
(B) The passage does not provide any information about the content of polar ice caps. (Out of scope)
(C) CORRECT. The sentence says that scientists discovered other similarities to Earth, implying that the earlier discovery (polar ice caps) is also similar to what is found on Earth.
(D) The passage mentions length of day and axial tilt as examples of other similarities to Earth, but it does not indicate that those had anything to do with the formation of polar ice caps. (Out of scope)
(E) It's possible that someone might believe this, but the passage does not provide any information to indicate that conditions were once very different. (Out of scope)
4. It can be inferred from the passage that scientists would be more likely to suspect that Mars once held life if there were evidence of which of the following features?
Difficulty Level: 600
Explanation
This is an inference question. Both paragraphs discuss characteristics that are possible indicators of life. Because there are so many, go straight to the answers and try to find them in the passage. But first, remind yourself that the passage also discusses characteristics that are incompatible with life. Read carefully!
(A)The second paragraph mentions that carbon dioxide oceans, rather than water, might be responsible for certain land forms, and the passage makes clear that water is an important indicator of possible life. Carbon dioxide oceans, then, would weaken the evidence for water presence, and so would not increase the chances of life. (Direct contradiction)
(B) The first paragraph mentions celestial radiation and solar wind in the context of a scenario in which there is not life. (Direct contradiction)
(C) You might posit that abundant sunlight would improve the odds of life, but the passage does not provide any information about this. (Out of scope)
(D) The passage does not provide any information about volcanic eruptions. (Out of scope)
(E) CORRECT. The first paragraph indicates that Mars, unlike Earth, does not have a substantial global magnetic field and presents this information as a negative in the debate about life on Mars. The implication, then, is that a global magnetic field would be positive evidence in favor of life on Mars.
Hope it helps