Mars’s Disappearing Atmosphere
For about the first billion years of its life, Mars was probably a watery planet. There are signs of past water in surface features, such as dried riverbeds, and in minerals that could only have formed in the presence of water. For there to have been water, early Mars must have had a thick atmosphere secured by a magnetic field. While Mars and Earth seem superficially similar, Earth has a magnetic field that helps to protect and retain its atmosphere, whereas Mars lost its magnetic field long ago, and its atmosphere is about 100 times thinner than Earth’s. Mars’s atmosphere may have disappeared in two different ways: up into space, and down into the ground (to become locked up within rocks and soil.) Observations by the spacecraft MAVEN have suggested that an “escape to space,” in which the solar wind (electrically charged particles streaming out from the Sun) strips away material from the upper parts of a planetary atmosphere, is probably most to blame. This process is still taking place today with what is left of the Martian atmosphere.
The solar wind streams into Mars’s vicinity, interacts with its atmosphere, and removes its uppermost ions (charged particles), dragging them out into space. The early Sun was far more volatile and active than the later Sun, flinging out bursts of radiation and producing solar storms far more frequently. This could have made any atmospheric stripping up to 20 times more devastating. Once Mars’s magnetic field switched off, after half a billion years or so, the planet’s upper atmosphere would have been naked, lacking its former shield. The solar wind could have streamed in and ionized molecules at a far higher rate, stripping them away faster.
There is also the fact that Mars is smaller, is less heavy, and thus has lower surface gravity than Earth. Accordingly, the planet simply struggles to keep hold of as much atmospheric material as Earth can. Mars’s atmosphere also may have been blasted out into space by the disastrous collisions with large objects we know to have taken place during its early history (which in turn would have made subsequent impacts even more destructive due to the thinner Martian atmosphere, continuing and worsening the cycle). In a less exciting scenario, Mars’s atmosphere might have just spun off into space of its own accord-the molecules may have swirled around and around, colliding and transferring energy between themselves, growing faster and faster until they moved fast enough to escape.
At least some of Mars’s atmosphere is thought to have headed down into the planet’s surface layer, interacting with the soil and combining with the elements present there, a process known as sequestration. We see signs of this process in the few Martian meteorites we have found here on Earth and in the explorations of the United States space agency’s Curiosity rover, which saw further signs when it arrived on Mars and began to study the soil and atmosphere in earnest. However, we have found that this is unlikely to have been a dominant process; we would expect the heavier parts of Mars’s atmosphere to have disappeared if it were, as they would have sunk down and been the ones to interact with the Martian surface. We see the opposite: instead of an atmosphere filled with lighter forms of the constituent elements, we see heavier ones. This suggests that Mars’s atmosphere was stripped from above and not below, thus removing more of the lighter elements and leaving the heavier ones behind. We would also expect to find carbonates, compounds that are a consequence of sequestration, in the Martian soil, but despite our various searches these do not seem to be present in large amounts.
We are still unsure of exactly what happened with Mars’s atmosphere but are fairly confident that the planet was once wrapped in a far thicker atmosphere that allowed the planet to stay warm and pressurized enough to support bodies of running and standing water. Mars’s ancient atmosphere was likely different in composition, with a far higher amount of oxygen, a necessary component of water We know this because we have found minerals in old Martian rock that need either an oxygen-rich environment or one with microorganisms present in order to form, and we do not believe it to have been the latter.
1
For about the first billion years of its life, Mars was probably a watery planet. There are signs of past water in surface features, such as dried riverbeds, and in minerals that could only have formed in the presence of water. For there to have been water, early Mars must have had a thick atmosphere secured by a magnetic field. While Mars and Earth seem superficially similar, Earth has a magnetic field that helps to protect and retain its atmosphere, whereas Mars lost its magnetic field long ago, and its atmosphere is about 100 times thinner than Earth’s. Mars’s atmosphere may have disappeared in two different ways: up into space, and down into the ground (to become locked up within rocks and soil.) Observations by the spacecraft MAVEN have suggested that an “escape to space,” in which the solar wind (electrically charged particles streaming out from the Sun) strips away material from the upper parts of a planetary atmosphere, is probably most to blame. This process is still taking place today with what is left of the Martian atmosphere.
According to paragraph 1, all of the following were probably true of early Mars EXCEPT:
Negative Factual Information Questions否定事实信息题
AIt had rivers flowing on its surface.
BIt had minerals that were formed in the presence of water.
CIt had a magnetic field.
DIt had an atmosphere that was 100 times thinner than Earth’s atmosphere today.
2
For about the first billion years of its life, Mars was probably a watery planet. There are signs of past water in surface features, such as dried riverbeds, and in minerals that could only have formed in the presence of water. For there to have been water, early Mars must have had a thick atmosphere secured by a magnetic field. While Mars and Earth seem superficially similar, Earth has a magnetic field that helps to protect and retain its atmosphere, whereas Mars lost its magnetic field long ago, and its atmosphere is about 100 times thinner than Earth’s. Mars’s atmosphere may have disappeared in two different ways: up into space, and down into the ground (to become locked up within rocks and soil.) Observations by the spacecraft MAVEN have suggested that an “escape to space,” in which the solar wind (electrically charged particles streaming out from the Sun) strips away material from the upper parts of a planetary atmosphere, is probably most to blame. This process is still taking place today with what is left of the Martian atmosphere.
The solar wind streams into Mars’s vicinity, interacts with its atmosphere, and removes its uppermost ions (charged particles), dragging them out into space. The early Sun was far more volatile and active than the later Sun, flinging out bursts of radiation and producing solar storms far more frequently. This could have made any atmospheric stripping up to 20 times more devastating. Once Mars’s magnetic field switched off, after half a billion years or so, the planet’s upper atmosphere would have been naked, lacking its former shield. The solar wind could have streamed in and ionized molecules at a far higher rate, stripping them away faster.
Which of the following best describes the relationship of paragraph 2 to paragraph 1 with regard to the discussion of the loss of Mars’s atmosphere?
Organization Questions组织结构题
AParagraph 2 discusses an alternative to the explanation said to be the most likely one in paragraph 1.
BParagraph 2 explains why the theory discussed in paragraph 1 is now considered to be correct.
CParagraph 2 suggests that the process identified in paragraph 1 can account for only part of what happened.
DParagraph 2 provides the details of the process that is introduced as a likely explanation in paragraph 1.
3
The solar wind streams into Mars’s vicinity, interacts with its atmosphere, and removes its uppermost ions (charged particles), dragging them out into space. The early Sun was far more volatile and active than the later Sun, flinging out bursts of radiation and producing solar storms far more frequently. This could have made any atmospheric stripping up to 20 times more devastating. Once Mars’s magnetic field switched off, after half a billion years or so, the planet’s upper atmosphere would have been naked, lacking its former shield. The solar wind could have streamed in and ionized molecules at a far higher rate, stripping them away faster.
According to paragraph 2, which TWO of the following factors caused Mars to lose its atmosphere at a fast rate? To receive credit, you must select TWO answer choices.
Factual Information Questions事实信息题
Select 2 answers
AThe Sun was closer to Mars in its early days.
BThe presence of ions out in space created bursts of radiation.
CThe early Sun frequently produced solar storms.
DMars lost its magnetic field, which had protected the atmosphere.
4
There is also the fact that Mars is smaller, is less heavy, and thus has lower surface gravity than Earth. Accordingly, the planet simply struggles to keep hold of as much atmospheric material as Earth can. Mars’s atmosphere also may have been blasted out into space by the disastrous collisions with large objects we know to have taken place during its early history (which in turn would have made subsequent impacts even more destructive due to the thinner Martian atmosphere, continuing and worsening the cycle). In a less exciting scenario, Mars’s atmosphere might have just spun off into space of its own accord-the molecules may have swirled around and around, colliding and transferring energy between themselves, growing faster and faster until they moved fast enough to escape.
The word“Accordingly”in the passage is closest in meaning to
Vocabulary Questions词汇题
AMost likely
BIn addition
CIn fact
DTherefore
5
There is also the fact that Mars is smaller, is less heavy, and thus has lower surface gravity than Earth. Accordingly, the planet simply struggles to keep hold of as much atmospheric material as Earth can. Mars’s atmosphere also may have been blasted out into space by the disastrous collisions with large objects we know to have taken place during its early history (which in turn would have made subsequent impacts even more destructive due to the thinner Martian atmosphere, continuing and worsening the cycle). In a less exciting scenario, Mars’s atmosphere might have just spun off into space of its own accord-the molecules may have swirled around and around, colliding and transferring energy between themselves, growing faster and faster until they moved fast enough to escape.
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
Sentence Simplification Questions句子简化题
AWhen the molecules in Mars’s atmosphere began aswirl ing around, they produced enough energy to cause them to collide and exchange some of that energy.
BIf the collisions of molecules had failed to produce enough energy, Mars’s atmosphere might have escaped into space of its own accord.
CMars might have lost its atmosphere because of its molecules colliding and gaining speed until they moved so fast that they escaped into space.
DThe collisions among the molecules in Mars’s atmosphere might have caused them to swirl around at a faster and faster rate.
6
At least some of Mars’s atmosphere is thought to have headed down into the planet’s surface layer, interacting with the soil and combining with the elements present there, a process known as sequestration. We see signs of this process in the few Martian meteorites we have found here on Earth and in the explorations of the United States space agency’s Curiosity rover, which saw further signs when it arrived on Mars and began to study the soil and atmosphere in earnest. However, we have found that this is unlikely to have been a dominant process; we would expect the heavier parts of Mars’s atmosphere to have disappeared if it were, as they would have sunk down and been the ones to interact with the Martian surface. We see the opposite: instead of an atmosphere filled with lighter forms of the constituent elements, we see heavier ones. This suggests that Mars’s atmosphere was stripped from above and not below, thus removing more of the lighter elements and leaving the heavier ones behind. We would also expect to find carbonates, compounds that are a consequence of sequestration, in the Martian soil, but despite our various searches these do not seem to be present in large amounts.
Which of the following can be inferred from paragraph 4 about the theory that Mars’s atmosphere disappeared into the surface of the planet?
Inference Questions推理题
AIt is not supported by the chemical analysis of Martian meteorites.
BIt is supported by newer investigations of the carbonate content of Martian soils.
CIt can explain only a small part of the loss of the planet’s atmosphere.
DIt is probably the best explanation for the loss of Mars’s atmosphere.
7
We are still unsure of exactly what happened with Mars’s atmosphere but are fairly confident that the planet was once wrapped in a far thicker atmosphere that allowed the planet to stay warm and pressurized enough to support bodies of running and standing water. Mars’s ancient atmosphere was likely different in composition, with a far higher amount of oxygen, a necessary component of water We know this because we have found minerals in old Martian rock that need either an oxygen-rich environment or one with microorganisms present in order to form, and we do not believe it to have been the latter.
The word”fairly” in the passage is closest in meaning to
Vocabulary Questions词汇题
Areasonably
Babsolutely
Ccautiously
Dincreasingly
8
We are still unsure of exactly what happened with Mars’s atmosphere but are fairly confident that the planet was once wrapped in a far thicker atmosphere that allowed the planet to stay warm and pressurized enough to support bodies of running and standing water. Mars’s ancient atmosphere was likely different in composition, with a far higher amount of oxygen, a necessary component of water We know this because we have found minerals in old Martian rock that need either an oxygen-rich environment or one with microorganisms present in order to form, and we do not believe it to have been the latter.
According to paragraph 5, which of the following evidence leads scientists to believe that Mars’s ancient atmosphere had much more oxygen than it has today?
Factual Information Questions事实信息题
ARock that could only have formed in temperatures warmed by a thick atmosphere
BThe presence of microorganisms in old Martian rock
CCertain minerals found in old Martian rock
DRock that seems to have been shaped by running and standing water
9
The solar wind streams into Mars’s vicinity, interacts with its atmosphere, and removes its uppermost ions (charged particles), dragging them out into space. The early Sun was far more volatile and active than the later Sun, flinging out bursts of radiation and producing solar storms far more frequently. This could have made any atmospheric stripping up to 20 times more devastating. ⬛Once Mars’s magnetic field switched off, after half a billion years or so, the planet’s upper atmosphere would have been naked, lacking its former shield. ⬛The solar wind could have streamed in and ionized molecules at a far higher rate, stripping them away faster.
⬛There is also the fact that Mars is smaller, is less heavy, and thus has lower surface gravity than Earth. ⬛Accordingly, the planet simply struggles to keep hold of as much atmospheric material as Earth can. Mars’s atmosphere also may have been blasted out into space by the disastrous collisions with large objects we know to have taken place during its early history (which in turn would have made subsequent impacts even more destructive due to the thinner Martian atmosphere, continuing and worsening the cycle). In a less exciting scenario, Mars’s atmosphere might have just spun off into space of its own accord-the molecules may have swirled around and around, colliding and transferring energy between themselves, growing faster and faster until they moved fast enough to escape.
Look at the four squaresthat indicate where the following sentence could be added to the passage
But the lack of a magnetic field and the Sun’s activity may not have been the only contributors to the loss of atmosphere.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Much research has been done on Mars’s past atmosphere.
Prose Summary Questions概要小结题
Select 3 answers
AIn order to have the pressure and temperature necessary to retain water, Mars’s early atmosphere must have been thicker than the planet’s current atmosphere.
BMost of Mars’s early atmosphere may have escaped into space as a result of the action of the solar wind on the upper atmosphere.
CThe surface gravity of Mars may have increased as a result of the heavier materials that sank down into the surface of Mars.
DAfter the upper atmosphere was lost, large objects from space entered and destroyed the remaining atmosphere at a far greater rate than earlier in the planet’s history.
ESome of the material in Mars’s early atmosphere could have entered the planet’s surface layer, where it interacted with the soil to form compounds that remained there.
FMartian rock samples recovered by recent space explorations suggest that Mars’s atmosphere today contains more oxygen than was previously thought to be present.
