Reading 3 "Life in Our Solar
System"
Although we can imagine life based on something other than carbon chemistry, we know of no examples to tell us how such life might arise and survive. We must limit our discussion to life as we know it and the conditions it requires. The most important requirement is the presence of liquid water, not only as part of the chemical reactions of life, but also as a medium to transport nutrients and wastes within the organism.
The water requirement {{U}}automatically{{/U}} eliminates many worlds in our solar system. The moon is airless, and although some data suggest ice frozen in the soil at its poles, it has never had liquid water on its surface. In the vacuum of the lunar surface, liquid water would boil away rapidly. Mercury too is airless and cannot have had liquid water on its surface for long periods of time. Venus has some traces of water vapor in its atmosphere, but it is much too hot for liquid water to survive. If there were any lakes or oceans of water on its surface when it was young, they must have evaporated quickly. Even if life began there, no traces would be left now.
The inner solar system seems too hot, and the outer solar system seems too cold. The Jovian planets have deep atmospheres, and at a certain level, they have moderate temperatures where water might condense into liquid droplets. But it seems unlikely that life could begin there. The Jovian planets have no surfaces where oceans could nurture the beginning of life, and currents in the atmosphere seem destined to circulate gas and water droplets from regions of moderate temperature to other levels that are much too hot or too cold for life to survive.
A few of the satellites of the Jovian planets might have suitable conditions for life. Jupiter's moon Europa seems to have a liquid-water ocean below its icy crust, and minerals dissolved in that water would provide a rich broth of possi- bilities for chemical evolution.
Nevertheless, Europa is not a
promising site to search for life because conditions may not have remained
{{U}}stable{{/U}} for the billions of years needed for life to evolve beyond the
microscopic stage.
If Jupiter's moons
interact gravitationally and modify their orbits, Europa may have been frozen
solid at some points in history. 
→ Saturn's moon Titan has an atmosphere of nitrogen, argon, and methane and may have oceans of liquid methane and ethane on its surface.
Although we can imagine life based on something other than carbon chemistry, we know of no examples to tell us how such life might arise and survive. We must limit our discussion to life as we know it and the conditions it requires. The most important requirement is the presence of liquid water, not only as part of the chemical reactions of life, but also as a medium to transport nutrients and wastes within the organism.
The water requirement {{U}}automatically{{/U}} eliminates many worlds in our solar system. The moon is airless, and although some data suggest ice frozen in the soil at its poles, it has never had liquid water on its surface. In the vacuum of the lunar surface, liquid water would boil away rapidly. Mercury too is airless and cannot have had liquid water on its surface for long periods of time. Venus has some traces of water vapor in its atmosphere, but it is much too hot for liquid water to survive. If there were any lakes or oceans of water on its surface when it was young, they must have evaporated quickly. Even if life began there, no traces would be left now.
The inner solar system seems too hot, and the outer solar system seems too cold. The Jovian planets have deep atmospheres, and at a certain level, they have moderate temperatures where water might condense into liquid droplets. But it seems unlikely that life could begin there. The Jovian planets have no surfaces where oceans could nurture the beginning of life, and currents in the atmosphere seem destined to circulate gas and water droplets from regions of moderate temperature to other levels that are much too hot or too cold for life to survive.
A few of the satellites of the Jovian planets might have suitable conditions for life. Jupiter's moon Europa seems to have a liquid-water ocean below its icy crust, and minerals dissolved in that water would provide a rich broth of possi- bilities for chemical evolution.
Nevertheless, Europa is not a
promising site to search for life because conditions may not have remained
{{U}}stable{{/U}} for the billions of years needed for life to evolve beyond the
microscopic stage.If Jupiter's moons
interact gravitationally and modify their orbits, Europa may have been frozen
solid at some points in history.
→ Saturn's moon Titan has an atmosphere of nitrogen, argon, and methane and may have oceans of liquid methane and ethane on its surface.
单选题
The word {{U}}automatically{{/U}} in the passage is closest in meaning to
【正确答案】
D
【答案解析】In this passage, naturally is a synonym for "automatically." Context comes from the prefix auto, which means "self" and the root matic, which is found in many words that refer to "machines."
单选题
The word {{U}}it{{/U}} in the passage refers to
【正确答案】
C
【答案解析】"The moon is airless, and although some data suggest ice frozen in the soil at its poles, it [the moon] has never had liquid water on its surface." The pronoun "it" does not refer to Choices A, B, or D.
单选题
Which of the following statements about the water on Venus is true?
【正确答案】
A
【答案解析】"Venus has some traces of water vapor in its atmosphere, but it is much too hot for liquid water to survive." Choice B is not correct because the water transformed to vapor, not ice. Ice refers to our moon, not to Venus. Choice C is not correct because the lakes or oceans evaporated quickly. Choice D is not correct because the airless atmosphere refers to Mercury, not to Venus.
单选题
The word {{U}}stable{{/U}} in the passage is closest in meaning to
【正确答案】
C
【答案解析】In this passage, constant is a synonym for "stable." Context comes from the contrast with "evolve" later in the sentence.
单选题
What can be inferred from the passage about the Jovian planets?
【正确答案】
B
【答案解析】Because Jupiter's moon is used as an example of satellites of Jovian planets, it must be concluded that Jupiter is a Jovian planet. Choice A is not correct because the satellites, not the planets, have conditions that support life. Choice C is not correct because the size of Europa is not mentioned. Choice D is not correct because the author draws no conclusion about the change of orbits. If orbits were modified, then a conclusion could be drawn about whether Europa was frozen.
单选题
According to paragraph 5, why would life on Titan be improbable?
【正确答案】
C
【答案解析】... life there may be unlikely because of the temperature. The surface of Titan is a deadly -179℃." Choice A is not correct because there are oceans of liquid methane and ethane. Choice B is true, but it is not the reason why life would be improbable. Choice D is not correct because it is the temperature, not the atmosphere, that is low.
单选题
Which of the sentences below best expresses the information in the
highlighted statement in the passage? The other choices change the meaning or
leave out important information.
【正确答案】
B
【答案解析】... the evidence did not demonstrate paraphrases "the results did not confirm."
单选题
The word {{U}}originated{{/U}} in the passage is closest in meaning to
【正确答案】
C
【答案解析】In this passage, begun is a synonym for"originated." Context comes from the root origin, which means "beginning."
单选题
Why does the author mention the meteorite ALH84001 in paragraph 6?
【正确答案】
C
【答案解析】"ALH84001 is important because a team of scientists studied it and announced in 1996 that it contained chemical and physical traces of ancient life on Mars." Choice A is not correct because the meteorite was found closer to twenty years ago. Choice B is not correct because the impact on Mars was not recent. Choice D is true, but it is not the reason why the author mentions the meteorite.
单选题
How will scientists confirm the existence of life on Mars?
【正确答案】
B
【答案解析】... conclusive evidence [of life] may have to wait until a geologist in a space suit can... open rocks... searching for fossils." Choice A is not correct because a geologist will travel in the spacecraft. Choice C is not correct because pictures are not mentioned as a way to confirm the existence of life on Mars. Choice D is not correct because the present conditions could be studied in a variety of ways, but conclusive evidence depends on a manned flight that will allow a geologist to study the physical evidence.
单选题
Which of the following statements most accurately reflects the
author's opinion about life in our solar system?
【正确答案】
C
【答案解析】"We are left to conclude that, so far as we know, our solar system is bare of life except for Earth." Choice A is not correct because the author states that our solar system is bare of life. Choice B is not correct because the evidence is not encouraging. Choice D is not correct because the search takes us to other planetary systems.
单选题
Look at the four squares [■] that show where the following sentence
could be inserted in the passage.
Such periods of freezing would probably prevent life from developing.
Where could the sentence best be added?
Click on a square [■] to insert the sentence in the passage.
Such periods of freezing would probably prevent life from developing.
Where could the sentence best be added?
Click on a square [■] to insert the sentence in the passage.
【正确答案】
C
【答案解析】Reference is a transitional device that connects the insert sentence with the previous sentence. Such periods refers to "some points in history." Choices A, B, and D are not correct because such periods does not refer to phrases in the sentences that precede the insert options.
填空题
Directions: An introduction for a short summary of
the passage appears below. Complete the summary by selecting the THREE answer
choices that mention the most important points in the passage. Some sentences do
not belong in the summary because they express ideas that are not included in
the passage or are minor points from the passage.
This question is worth 2 points.
Current evidence does not support the theory of life in our solar system.
·__________
·__________
·__________
A. The meteorite that was discovered in the Antarctic in the 1980s was thought to contain evidence of early life on Mars, but it was later disputed.
B. The planet that has the greatest proba- bility for life in the past or now is Mars, but more investigation is required to draw conclusions.
C. Europa has an ocean under the ice on the surface of the moon, which may contain the chemical combinations required for life to evolve.
D. Although some of the moons that revolve around Saturn and Jupiter have condi- tions that might support life, the evidence contradicts this possibility.
E. Other planetary systems must have life that is similar to that which has evolved on Earth because of the principles of carbon chemistry.
F. It is too hot for life on the planets near the Sun in the inner solar system and too cold on the planets most removed from the Sun in the outer solar system.
This question is worth 2 points.
Current evidence does not support the theory of life in our solar system.
·__________
·__________
·__________
Answer Choices
A. The meteorite that was discovered in the Antarctic in the 1980s was thought to contain evidence of early life on Mars, but it was later disputed.
B. The planet that has the greatest proba- bility for life in the past or now is Mars, but more investigation is required to draw conclusions.
C. Europa has an ocean under the ice on the surface of the moon, which may contain the chemical combinations required for life to evolve.
D. Although some of the moons that revolve around Saturn and Jupiter have condi- tions that might support life, the evidence contradicts this possibility.
E. Other planetary systems must have life that is similar to that which has evolved on Earth because of the principles of carbon chemistry.
F. It is too hot for life on the planets near the Sun in the inner solar system and too cold on the planets most removed from the Sun in the outer solar system.