IELTS Academic Reading Practice 76

 
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This reading practice simulates one part of the IELTS Academic Reading test. You should spend about twenty minutes on it. Read the passage and answer questions 1-14.

Questions 1-5

Complete each sentence with the correct ending A-L from the box below.

Write the correct letter A-L in boxes 1-5 on your answer sheet.

NB You may use any letter more than once.

1 Dwarf planets …
2 Callisto …
3 Scientists expected that …
4 The four moons of Jupiter …
5 Ganymede ...

  1. Callisto may be a rocky body rather than an icy one
  2. are likely to have been born from a circumplanetary disk.
  3. has a core that consists mainly of rock and metal.
  4. originated from remnants of asteroids captured by Jupiter’s gravitational pull.
  5. are smaller than asteroids that orbit Jupiter
  6. Callisto to be differentiated.
  7. has surface temperature that is constant at all times of the day.
  8. Callisto could not differentiate because it was frozen solid
  9. are larger than asteroids and orbit the sun
  10. has the same mass and diameter as the planet Mercury
  11. is the satellite closest to Jupiter's surface
  12. completes one rotation every seventeen days.
Questions 6-10

Do the following statements agree with the information given in the reading passage? In boxes 6-10 on your answer sheet, write

TRUE   if the statement agrees with the information
FALSE   if the statement contradicts the information
NOT GIVEN   if there is no information on this

6. A spate of technological developments with telescopes and telescopic photography leading to the discovery of 13 moons.
7. The further away the surface ice is from the Sun, the more its temperature differs from that of the warmer ice on Earth.
8. Ganymede’s interior is not fully solid.
9. Each generation of moons thickened the circumplanetary disk.
10. The large moons of Jupiter gradually broke up into small irregular-shaped moons.
Questions 11-14

Choose the correct letter, A, B, C or D.

Write your answers in boxes 11-14 on your answer sheet.

11 How do scientists know that Callisto is made up largely of ice?

12 how is Callisto different from all other planet-sized objects in the solar system?

13 Each of the following provides evidence about Ganymede's interior EXCEPT

14 The differences in how Callisto and Ganymede evoked are most probably due to differences in their …


Answer Sheet
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The Moons of Jupiter

For most, the largest planet in our solar system, Jupiter, is best known for its vast size. However, Jupiter is also remarkable for many moons which orbit around it. Well-known astronomer Galileo Galilei was the first to discover the four most famous moons, though they were given their present names by another astronomer of the time, Simon Marius. The names of Jupiter's remaining moons were inspired by conquests, gods, lovers, and family. Some of the moons are comparable in size to small asteroids, while the Galilean moons are closer to the size of Earth’s moon. If orbiting the sun rather than the planet Jupiter, these four moons might be large enough to be considered dwarf planets. Since the initial discovery of Jupiter’s moons, scientists’ fascination with them has continued for centuries, with questions surrounding the moons’ relatively unknown origins, as well as their variable qualities.  

In the year 1609, Galileo Galilei made his first attested discovery of the moons. By using a 30x magnification telescope, the following year Galileo became the first to more closely observe what are now known as the Galilean moons. The four moons, Ganymede, Callisto, Io, and Europa, were the first objects ever discovered in our solar system which orbited neither the Earth nor the Sun, and this remained the case until the year 1892 when E.E. Barnard discovered the moon Amalthea. Throughout the 20th century, advancements in technology related to telescopes and telescopic photography brought about the discovery of another 13 moons by the year 1979. That same year, the United States reached Jupiter with space probes launched previously to begin further observations of the planet.

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 in 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. 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.

According to scientists, there may have been other moons similar in size and mass to the Galilean moons orbiting Jupiter over the course of the planet’s history. Early moons could have been formed by a circumplanetary disk, gathered by different types of gas and solid debris, similar to a protoplanetary disk. Over a period of time, it seems there may have been generations of large moons as a result of the circumplanetary disk. The disappearance of these past larger moons may be explained by many generations of large moons which caused the disk to thin, until eventually the Galilean moons were the only ones able to be protected by an orbital resonance. Apart from the four larger Galilean moons, Jupiter’s other current moons most likely formed by asteroids passing the planet which were then captured into orbit. Groups of these small moons are most likely the remains of asteroids which broke apart either by collisions with other small moons or by the stress of being captured into orbit. Overall, Jupiter’s accumulation of numerous moons over millions of years can best be attributed to its mass and gravitational pull.

Reading Passage Vocabulary
The Moons of Jupiter

For most, the largest planet in our solar system, Jupiter, is best known for its vast size. However, Jupiter is also remarkable for many moons which orbit around it. Well-known astronomer Galileo Galilei was the first to discover the four most famous moons, though they were given their present names by another astronomer of the time, Simon Marius. The names of Jupiter's remaining moons were inspired by conquests, gods, lovers, and family. Some of the moons are comparable in size to small asteroids, while the Galilean moons are closer to the size of Earth’s moon. If orbiting the sun rather than the planet Jupiter, these four moons might be large enough to be considered dwarf planets. Since the initial discovery of Jupiter’s moons, scientists’ fascination with them has continued for centuries, with questions surrounding the moons’ relatively unknown origins, as well as their variable qualities.  

In the year 1609, Galileo Galilei made his first attested discovery of the moons. By using a 30x magnification telescope, the following year Galileo became the first to more closely observe what are now known as the Galilean moons. The four moons, Ganymede, Callisto, Io, and Europa, were the first objects ever discovered in our solar system which orbited neither the Earth nor the Sun, and this remained the case until the year 1892 when E.E. Barnard discovered the moon Amalthea. Throughout the 20th century, advancements in technology related to telescopes and telescopic photography brought about the discovery of another 13 moons by the year 1979. That same year, the United States reached Jupiter with space probes launched previously to begin further observations of the planet.

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 in 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. 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.

According to scientists, there may have been other moons similar in size and mass to the Galilean moons orbiting Jupiter over the course of the planet’s history. Early moons could have been formed by a circumplanetary disk, gathered by different types of gas and solid debris, similar to a protoplanetary disk. Over a period of time, it seems there may have been generations of large moons as a result of the circumplanetary disk. The disappearance of these past larger moons may be explained by many generations of large moons which caused the disk to thin, until eventually the Galilean moons were the only ones able to be protected by an orbital resonance. Apart from the four larger Galilean moons, Jupiter’s other current moons most likely formed by asteroids passing the planet which were then captured into orbit. Groups of these small moons are most likely the remains of asteroids which broke apart either by collisions with other small moons or by the stress of being captured into orbit. Overall, Jupiter’s accumulation of numerous moons over millions of years can best be attributed to its mass and gravitational pull.

 
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