Jupiter, the fifth planet from the Sun and the largest in the solar system, is orbited by 69 moons, including lo, Europa, Ganymede, and Callisto. Europa, which is of the same size as our Moon, shows crisscrossing cracks in the surface that change on time scales of weeks or months. To expert geologists and planetary scientists, this behavior implies that Europa has a surface made almost entirely of water ice, like a giant Antarctic ice sheet enclosing an entire world. And the changing appearance of the cracks in this icy surface leads to a startling conclusion: the ice apparently floats on a worldwide ocean. Only by assuming the existence of liquid beneath the icy surface can scientists satisfactorily explain what they have seen, thanks to the stunning successes of the Voyager and Galileo spacecraft, which were sent to study Jupiter and its moons. Since we observe changes on the surface all around Europa, we may conclude that a worldwide ocean of liquid must underlie that surface.
What liquid could this be, and why should that substance remain liquid? Impressively, planetary scientists have reached two fairly firm additional conclusions: the liquid is water, and it remains liquid because of tidal(gravitational) effects on Europa produced by the giant planet Jupiter. The fact that water molecules are more abundant than ammonia, ethane, or methyl alcohol makes it the likeliest substance to provide the liquid beneath Europa’s ice, and the existence of this frozen water likewise implies that more water exists in the immediate neighborhood. But how can water remain a liquid, when the solar-induced temperatures in Jupiter’s vicinity are only about-150° Celsius? Europa’s interior remains relatively warm because tidal forces from Jupiter and the two large moons nearby, lo and Ganymede, continuously flex (bend) the rocks within Europa as this moon changes its position with respect to neighboring objects. At all times, the sides of lo and Europa closest to Jupiter feel a stronger force of gravity from the giant planet than the sides farthest away. These differences in force slightly elongate the solid moons in the direction facing Jupiter. But as the moons’ distances from Jupiter change during their orbits, Jupiter’s tidal effect-the difference in force exerted on the near side and the far side-also changes, producing small pulses in their already distorted shapes. This changing distortion heats the moons’interiors. Like a rubber ball, for example a squash ball or a racquet ball, continually being deformed by impact, any system that undergoes continuing structural stress will have its internal temperature rise.
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
Astrobiologists(scientists who look for extraterrestrial life) therefore view Europa’s worldwide ocean as a prime target for investigation. No one knows the ice cap’s thickness, which might range from a few dozen meters to about a kilometer or more. Given the abundance of life within Earth’s oceans, Europa remains the most tantalizing place in the solar system to search for life outside of Earth. Indeed, scientists have begun to envision a space probe that lands, finds (or cuts) a hole in the ice, and drops a submersible camera to see if primitive life exists below.
1
Jupiter, the fifth planet from the Sun and the largest in the solar system, is orbited by 69 moons, including lo, Europa, Ganymede, and Callisto. Europa, which is of the same size as our Moon, shows crisscrossing cracks in the surface that change on time scales of weeks or months. To expert geologists and planetary scientists, this behavior implies that Europa has a surface made almost entirely of water ice, like a giant Antarctic ice sheet enclosing an entire world. And the changing appearance of the cracks in this icy surface leads to a startling conclusion: the ice apparently floats on a worldwide ocean. Only by assuming the existence of liquid beneath the icy surface can scientists satisfactorily explain what they have seen, thanks to the stunning successes of the Voyager and Galileo spacecraft, which were sent to study Jupiter and its moons. Since we observe changes on the surface all around Europa, we may conclude that a worldwide ocean of liquid must underlie that surface.
According to paragraph 1， why do scientists think that a liquid ocean exists under Europa’s surface?
AOther moons orbiting Jupiter have worldwide liquid oceans.
BThe cracks on Europa’s surface change repeatedly over time.
CScientists have identified areas of liquid water on Europa’s surface.
DWater ice on the surface of Europa is similar to a giant Antarctic ice sheet.
2
Jupiter, the fifth planet from the Sun and the largest in the solar system, is orbited by 69 moons, including lo, Europa, Ganymede, and Callisto. Europa, which is of the same size as our Moon, shows crisscrossing cracks in the surface that change on time scales of weeks or months. To expert geologists and planetary scientists, this behavior implies that Europa has a surface made almost entirely of water ice, like a giant Antarctic ice sheet enclosing an entire world. And the changing appearance of the cracks in this icy surface leads to a startling conclusion: the ice apparently floats on a worldwide ocean. Only by assuming the existence of liquid beneath the icy surface can scientists satisfactorily explain what they have seen, thanks to the stunning successes of the Voyager and Galileo spacecraft, which were sent to study Jupiter and its moons. Since we observe changes on the surface all around Europa, we may conclude that a worldwide ocean of liquid must underlie that surface.
Paragraph 1 supports all of the following statements about Europa EXCEPT:
AIt is the fifth-largest moon orbiting Jupiter.
BIt is one of Jupiter’s 69 moons.
CIt is about as big as Earth’s Moon.
DIt has been studied with the help of spacecraft.
3
What liquid could this be, and why should that substance remain liquid? Impressively, planetary scientists have reached two fairly firm additional conclusions: the liquid is water, and it remains liquid because of tidal(gravitational) effects on Europa produced by the giant planet Jupiter. The fact that water molecules are more abundant than ammonia, ethane, or methyl alcohol makes it the likeliest substance to provide the liquid beneath Europa’s ice, and the existence of this frozen water likewise implies that more water exists in the immediate neighborhood. But how can water remain a liquid, when the solar-induced temperatures in Jupiter’s vicinity are only about-150° Celsius? Europa’s interior remains relatively warm because tidal forces from Jupiter and the two large moons nearby, lo and Ganymede, continuously flex (bend) the rocks within Europa as this moon changes its position with respect to neighboring objects. At all times, the sides of lo and Europa closest to Jupiter feel a stronger force of gravity from the giant planet than the sides farthest away. These differences in force slightly elongate the solid moons in the direction facing Jupiter. But as the moons’ distances from Jupiter change during their orbits, Jupiter’s tidal effect-the difference in force exerted on the near side and the far side-also changes, producing small pulses in their already distorted shapes. This changing distortion heats the moons’interiors. Like a rubber ball, for example a squash ball or a racquet ball, continually being deformed by impact, any system that undergoes continuing structural stress will have its internal temperature rise.
Which of the following causes “continuing structural stress”in Europa?
AThe effects of low solar-induced temperatures on Europa’s liquid water
BThe gradual increase of Europa’s internal temperature over time
CThe tidal forces from Jupiter and other moons in Europa’s vicinity
DThe deformation caused by impact from objects hitting Europa’s surface
4
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
The word “guarantee” in the passage is closest in meaning to
Acreate
Bsuggest
Censure
Dmaintain
5
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
Why does the author provide the information that Europa “undergoes less tidal flexing than lo”?
ATo explain why Europa has liquid water and lo does not
BTo help readers understand how much farther Europa is from Jupiter than lo is
CTo illustrate an effect of compounds released by lo’s volcanoes
DTo suggest that Europa’s main source of heat is very different from lo’s
6
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
The phrase “more modestly”in the passage is closest in meaning to
Ain a more predictable way
Bin a more limited way
Cmore evenly
Dmore infrequently
7
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
Paragraph 3 suggests which of the following about the early Earth?
AIt was a frozen ice world.
BIt was farther from the Sun than today’s Earth is.
CIt had no erupting volcanoes, surface fissures, or plate tectonics.
DIt was more geologically active than today’s Earth is.
8
With a distance from the Sun that would otherwise guarantee a forever-frozen ice world, the stress level inside lo (Jupiter’s nearest moon)earns it the title of the most geologically active place in the entire solar system-complete with erupting volcanoes, surface fissures, and plate tectonics. Some have compared modern-day lo to the early Earth, when our planet was still extremely hot from its episode of formation. Inside lo, the temperature rises to the point that volcanoes continually blast foul-smelling compounds of sulfur and sodium many miles above the satellite’s surface. Io in fact has too high a temperature for liquid water to survive, but Europa, which undergoes less tidal flexing than lo because it is farther from Jupiter, heats more modestly, though still significantly. In addition, Europa’s worldwide ice cap puts a pressure lid on the liquid below, preventing the water from evaporating and allowing it to exist for billions of years without freezing. So far as we can tell, Europa was born with its water ocean and ice above, and has maintained that ocean, close to the freezing point but still above it, for the four and a half billion years since its formation.
According to paragraph 3， all of the following statements about Europa’s ocean are true EXCEPT:
AIt has grown much larger in the four and a half billion years since it was formed.
BIt remains liquid in part because of pressure from ice above it.
CIt is only a little warmer than the freezing point of water.
DIt has always existed since Europa was formed.
9
Jupiter, the fifth planet from the Sun and the largest in the solar system, is orbited by 69 moons, including lo, Europa, Ganymede, and Callisto. [■] Europa, which is of the same size as our Moon, shows crisscrossing cracks in the surface that change on time scales of weeks or months. [■] To expert geologists and planetary scientists, this behavior implies that Europa has a surface made almost entirely of water ice, like a giant Antarctic ice sheet enclosing an entire world. And the changing appearance of the cracks in this icy surface leads to a startling conclusion: the ice apparently floats on a worldwide ocean. [■] Only by assuming the existence of liquid beneath the icy surface can scientists satisfactorily explain what they have seen, thanks to the stunning successes of the Voyager and Galileo spacecraft, which were sent to study Jupiter and its moons.[■] Since we observe changes on the surface all around Europa, we may conclude that a worldwide ocean of liquid must underlie that surface.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Some of them have generated interest from scientists because of their unusual characteristics.
Where would the sentence best fit？Click on a square sentence to the passage.
10
Scientists have studied the characteristics of some of Jupiter’s moons.
AOf Jupiter’s 69 moons, lo and Europa are the largest of the four that geologists and planetary scientists believe to contain water in some form.
BThe force of Jupiter’s gravity continuously distorts Europa and lo in different ways depending on where the moons are in their orbits around the planet, and this causes flexing of rocks within the moons.
CIn our solar system, lo is the most geologically active place and too hot to have liquid water, while Europa, with its water, is the most promising place to find extraterrestrial life.
DEuropa is completely covered by ice floating on water that remains liquid because the interior of the moon is warm.
ESpacecraft have provided a great deal of information on Europa, and scientists now hope to send space probes to lo and some of Jupiter’s other moons that have been more difficult to investigate.
FThe cracks in Europa’s icy surface lead some scientists to believe that its ice cap is slowly melting, which is one reason that its oceans continue to exist and grow.
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