托福阅读TPO42真题Part3阅读原文
Callisto and Ganymede
From 1996 to 1999, the Galileo spacecraft passed through the Jovian system, providing much information about Jupiter's satellites. Callisto, the outermost of Jupiter's four largest satellites, orbits the planet in seventeen days at a distance from Jupiter of two million kilometers. Like our own Moon. Callisto rotates in the same period as it revolves, so it always keeps the same face toward Jupiter. Its noontime surface temperature is only about -140°C, so water ice is stable on its surface year-round. Callisto has a diameter of 4.820 kilometers, almost the same as that of Mercury. Its mass is only one-third as great, which means its density must be only one-third as great as well. This tells us that Callisto has far less of the rocky metallic materials found in the inner planets and must instead be an icy body through much of its interior.
Callisto has not fully differentiated, meaning separated into layers of different density materials. Astronomers can tell that it lacks a dense core from the details of its gravitational pull on the Galileo spacecraft during several very close flybys. This fact surprised scientists, who expected that all the big icy moons would be differentiated. It is much easier for an icy body to differentiate than for a rocky one, since the melting temperature of ice is so low. Only a little heating will soften the ice and get the process started, allowing the rock and metal to sink to the center and the slushy ice to float to the surface. Yet Callisto seems to have frozen solid before the process of differentiation was complete.
Like our Moon's highlands, the surface of Callisto is covered with impact craters. The survival of these craters tells us that an icy object can form and retain impact craters m its surface. In thinking of ice so far from the Sun, it is important not to judge its behavior from that of the much warmer ice we know on Earth; at the temperatures of the outer solar system, ice on the surface is nearly as hard as rock, and behaves similarly. Ice on Callisto does not deform or flow like ice in glaciers on Earth. Callisto is unique among the planet-sized objects of the solar system in its absence of interior forces to drive geological evolution. The satellite was born dead and has remained geologically dead for more than four billion years.
Ganymede, another of Jupiter's satellites and the largest in our solar system, is also cratered, but less so than Callisto. About one-quarter of its surface seems to be as old and heavily cratered; the rest formed more recently, as we can tell by the sparse covering of impact craters as well as the relative freshness of the craters. Ganymede is a differentiated world, like the terrestrial planets. Measurements of its gravity field tell us that the rock and metal sank to form a core about the size of our Moon, with a mantle and crust of ice floating above it. In addition, the Galileo spacecraft discovered that Ganymede has a magnetic field, the signature of a partially molten interior. Ganymede is not a dead world, but rather a place of continuing geological activity powered by an internal heat source. Much of its surface may be as young as half a billion years.
The younger terrain is the result of tectonic and volcanic forces Some features formed when the crust cracked, flooding many of the craters with water from the interior. Extensive mountain ranges were formed from compression of the crust, forming long ridges with parallel valleys spaced one to two kilometers apart. In some places older impact craters were split and pulled apart. There are even indications of large-scale crustal movements that are similar to the plate tectonics of Earth.
Why is Ganymede different from Callisto? Possibly the small difference in size and internal heating between the two led to this divergence in their evolution. But more likely the gravity of Jupiter is to blame for Ganymede's continuing geological activity. Ganymede is close enough to Jupiter that tidal forces from the giant planet may have episodically heated its interior and triggered major convulsions on its crust.
托福阅读TPO42真题及答案Part3阅读题目
paragraph 1
From 1996 to 1999, the Galileo spacecraft passed through the Jovian system, providing much information about Jupiter's satellites. Callisto, the outermost of Jupiter's four largest satellites, orbits the planet in seventeen days at a distance from Jupiter of two million kilometers. Like our own Moon. Callisto rotates in the same period as it revolves, so it always keeps the same face toward Jupiter. Its noontime surface temperature is only about -140°C, so water ice is stable on its surface year-round. Callisto has a diameter of 4.820 kilometers, almost the same as that of Mercury. Its mass is only one-third as great, which means its density must be only one-third as great as well. This tells us that Callisto has far less of the rocky metallic materials found in the inner planets and must instead be an icy body through much of its interior.
1.According to paragraph 1, which of the following statements about Callisto is true?
A.It is the satellite closest to Jupiter's surface
B.Its surface temperature is constant at all times of the day.
C. It has the same mass and diameter as the planet Mercury
D. It completes one rotation every seventeen days.
2. According to paragraph 1, how do scientists know that Callisto is made up largely of ice?
A. A sample of its interior was taken by the Galileo spacecraft in the late 1990s
B. It has too low a density to contain much rocky metallic material
C. With a noontime surface temperature of only about .140° C. the ice on it never melts
D. All of the bodies in the Jovian system are icy, because they are so far from the Sun.
paragraph 2
Callisto has not fully differentiated, meaning separated into layers of different density materials. Astronomers can tell that it lacks a dense core from the details of its gravitational pull on the Galileo spacecraft during several very close flybys. This fact surprised scientists, who expected that all the big icy moons would be differentiated. It is much easier for an icy body to differentiate than for a rocky one, since the melting temperature of ice is so low. Only a little heating will soften the ice and get the process started, allowing the rock and metal to sink to the center and the slushy ice to float to the surface. Yet Callisto seems to have frozen solid before the process of differentiation was complete.
3.Why does the author provide the information that “It is much easier for an icy body to differentiate than for a rocky one”?
A. To support the claim that all of the big icy moons are differentiated
B. To suggest that Callisto may be a rocky body rather than an icy one
C. To explain why scientists expected Callisto to be differentiated
D. To refute the claim that Callisto could not differentiate because it was frozen solid
4.All of the following questions are answered in paragraph 2 EXCEPT:
A.Why was Callisto frozen solid before differentiation was complete?
B.What allows the process of differentiation to get started?
C. Why is it easier for an icy body to differentiate than a rocky one?
D. How do astronomers know that Callisto lacks a dense core?
paragraph 3
Like our Moon's highlands, the surface of Callisto is covered with impact craters. The survival of these craters tells us that an icy object can form and retain impact craters m its surface. In thinking of ice so far from the Sun, it is important not to judge its behavior from that of the much warmer ice we know on Earth; at the temperatures of the outer solar system, ice on the surface is nearly as hard as rock, and behaves similarly. Ice on Callisto does not deform or flow like ice in glaciers on Earth. Callisto is unique among the planet-sized objects of the solar system in its absence of interior forces to drive geological evolution. The satellite was born dead and has remained geologically dead for more than four billion years.
5. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
A. It should not be assumed that surface ice has the same characteristics wherever it is found
B. Surface ice and rock are much more similar in temperature in the outer solar system than they are on Earth.
C. The further away surface ice is from the Sun, the more its temperature differs from that of the warmer ice on Earth
D. In the cold of the outer solar system, surface ice is so hard it behaves more like rock than like the warmer ice on Earth
6.According to paragraph 3, how is Callisto different from all other planet-sized objects in the solar system?
A. It can form and retain impact craters on its icy surface
B. It has ice glaciers that do not flow or deform.
C. It has never had the interior forces required for geological evolution.
D. It is more than four billion years old.
paragraph 4
Ganymede, another of Jupiter's satellites and the largest in our solar system, is also cratered, but less so than Callisto. About one-quarter of its surface seems to be as old and heavily cratered; the rest formed more recently, as we can tell by the sparse covering of impact craters as well as the relative freshness of the craters. Ganymede is a differentiated world, like the terrestrial planets. Measurements of its gravity field tell us that the rock and metal sank to form a core about the size of our Moon, with a mantle and crust of ice floating above it. In addition, the Galileo spacecraft discovered that Ganymede has a magnetic field, the signature of a partially molten interior. Ganymede is not a dead world, but rather a place of continuing geological activity powered by an internal heat source. Much of its surface may be as young as half a billion years.
7.The word “signature” in the passage is closest in meaning to
A.primary cause
B.end result
C.identifying mark
D.by-product
8. According to paragraph 4, each of the following provides evidence about Ganymede's interior EXCEPT
A. Ganymede's large size
B. measurements of Ganymede's gravity field
C. the fact that Ganymede has a magnetic field
D. the fact that Ganymede continues to be geologically active
paragraph 5
The younger terrain is the result of tectonic and volcanic forces Some features formed when the crust cracked, flooding many of the craters with water from the interior. Extensive mountain ranges were formed from compression of the crust, forming long ridges with parallel valleys spaced one to two kilometers apart. In some places older impact craters were split and pulled apart. There are even indications of large-scale crustal movements that are similar to the plate tectonics of Earth.
9.The word “Extensive” in the passage is closet in meaning to
A.Unusual
B.Large
C.New
D.Steep
10. Paragraph 5 supports each of the following statements about Ganymede EXCEPT:
A. All water on it has always been frozen solid.
B. There is evidence that part of its crust once broke open
C. Its crust has been subject to forces that have created mountains and valleys.
D. Some of its older craters have been split apart by more recent geological activity
paragraph 6
Why is Ganymede different from Callisto? Possibly the small difference in size and internal heating between the two led to this divergence in their evolution. But more likely the gravity of Jupiter is to blame for Ganymede's continuing geological activity. Ganymede is close enough to Jupiter that tidal forces from the giant planet may have episodically heated its interior and triggered major convulsions on its crust.
11. According to paragraph 6, the differences in how Callisto and Ganymede evoked are most probably due to differences in their
A. size and internal heating
B. distance from Jupiter
C. chemical and physical composition
D. age
12.Look at the four squares [■] that indicate where the following sentence could be added to the passage.
The?difference?between?Ganymede?and?Callisto,?however,?extend?much?further?below?the? surface?of?the?satellites.
Where would the sentence best fit? Click on square [■] to add the sentence to the passage
Ganymede, another of Jupiter's satellites and the largest in our solar system, is also cratered, but less so than Callisto. [■] About one-quarter of its surface seems to be as old and heavily cratered; the rest formed more recently, as we can tell by the sparse covering of impact craters as well as the relative freshness of the craters. [■] Ganymede is a differentiated world, like the terrestrial planets. [■] Measurements of its gravity field tell us that the rock and metal sank to form a core about the size of our Moon, with a mantle and crust of ice floating above it. [■] In addition, the Galileo spacecraft discovered that Ganymede has a magnetic field, the signature of a partially molten interior. Ganymede is not a dead world, but rather a place of continuing geological activity powered by an internal heat source. Much of its surface may be as young as half a billion years.
13. Directions:An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selected THREE answer choices that express the most important ideas in the passage.Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.This question is worth 2 points.
Drag your choices to the spaces where they belong. To review the passage, click on View Text
Between 600 B.C. and 450 B.C., Athens changed the distribution of political power between the aristocracy and ordinary citizens.
Callisto
Ganymede
阅读三
Answer Choices
A. It has a core that consists mainly of rock and metal.
B. It may have formed as recently as half a billion years ago
C. Its interior is not fully solid
D. Its evolution has probably been strongly influenced by Jupiter's gravity
E. It always keeps the same face toward Jupiter as it orbits the planet
F. Its crust is covered by slow-moving glaciers
G. Its entire surface is heavily cratered
托福阅读TPO42真题及答案Part阅读答案：
1-5 D B C A D 6-10 C C A B A 11-12 B B
13 Callisto：EG;Ganymede：CAD