The Moon’s Origin
One of the earliest scientific theories about the Moon’s origin postulated that Earth and its moon formed out of a dust cloud alongside one another, much as we see them today. However, when careful measurements of the lunar orbit were made, they showed that it was not steady but was changing with time. So a new theory arose. This theory held that the Moon formed independently of Earth elsewhere in the solar system and was captured by Earth’s gravity as it crossed Earth’s orbit. If our Moon were formed elsewhere, such an alien moon would have a different geological history and structure than Earth, reflecting the region of the solar system in which it was formed. The Earth capture theory fell out of favor when it was found that the Moon’s geology and planetary characteristics closely resembled Earth’s. However, in the 1980s, it was revived with the realization that some meteorites that had struck the Earth were of lunar origin and differed slightly from terrestrial rocks.
Towards the end of the twentieth century, a more advanced and informed theory developed, postulating that the Moon was born following a cataclysmic collision between early Earth and another planetary object with an irregular orbit that crossed Earth’s orbit. This collision would have occurred around 4.5 billion years ago, when the smaller early (or “proto-“) Earth was still largely molten and not quite yet solidified. The colliding object would have been roughly the size of Mars and has been given the name Theia. The collision was so cataclysmic that it knocked Earth off its axis, resulting in the current 23.5 tilt we see today. The tilt, now stabilized by the Moon, gives us our seasons during each orbit of the Sun. The impact was so catastrophic that the proto-Earth fractured and any early atmosphere was lost, with Theia being largely destroyed. The majority of the pulverized Theia mixed with Earth, and the remaining ejected debris formed a hot disc of vapor and material around the planet, much like the rings of Saturn. Then, over many centuries, some of the orbiting debris fell to Earth and mixed with the cooling surface, while the remainder coalesced to form the orbiting Moon. This created a Moon with a similar geological composition to that of Earth, with Theia’s unique characteristics being completely obliterated in the process.
This theory has some limitations. While it requires the total destruction of Theia, it also requires that the orbiting ejected material would have to remain very hot for a long time to allow sufficient mixing to occur. It is very difficult to achieve this level of heating from a head-on collision. Thus, a more recent theory suggests that the collision was not head-on but was more like a high-speed glancing blow. This sort of collision creates the heat required, and, if this theory is correct, then, somewhere in the solar system a remnant of Theia may still survive.
The collision with Theia left Earth with a heavy molten-iron, radioactive core, giving it the ability to generate heat and a protective magnetic field. The Moon was left with only a small molten-iron core and a very weak magnetic field. Since then, the dynamic interaction between the liquid portion of Earth’s core and its hard outer layer, the mantle, ensures that Earth’s surface has been in continuous flux and the surface is always being subsumed or reformed through various geological processes somewhere in the world. While orbiting debris would have rained down onto the surface of the cooling Earth and Moon for millennia, there is scant evidence of this debris on Earth, as it has been lost in the continual geological reshaping and later weathering of the surface.
Remarkably, on the Moon, a large proportion of the original surface remains just as it formed those many billions of years ago. While the surface is not flat and has undergone some volcanism of its own, there are plenty of valleys and mountains left over from this era. While moonquakes do occur, they do not alter the surface and are small-more like tremors. The Moon’s surface therefore provides a record not only of the Moon of billions of years ago, but of all the impacts that have rained down on its surface throughout its lifetime.
1
One of the earliest scientific theories about the Moon’s origin postulated that Earth and its moon formed out of a dust cloud alongside one another, much as we see them today. However, when careful measurements of the lunar orbit were made, they showed that it was not steady but was changing with time. So a new theory arose. This theory held that the Moon formed independently of Earth elsewhere in the solar system and was captured by Earth’s gravity as it crossed Earth’s orbit. If our Moon were formed elsewhere, such an alien moon would have a different geological history and structure than Earth, reflecting the region of the solar system in which it was formed. The Earth capture theory fell out of favor when it was found that the Moon’s geology and planetary characteristics closely resembled Earth’s. However, in the 1980s, it was revived with the realization that some meteorites that had struck the Earth were of lunar origin and differed slightly from terrestrial rocks.
It can be inferred from paragraph 1 that, if Earth and the Moon had formed together out of a single dust cloud, which of the following would be true?
Inference Questions推理题
AEarth’s gravity would be weaker than it is.
BThe dust cloud would have been elsewhere in the solar system than where Earth and the Moon are now.
CEarth and the Moon would have differing geological histories and structures
DThe lunar orbit would be stable and unchanging over time
2
One of the earliest scientific theories about the Moon’s origin postulated that Earth and its moon formed out of a dust cloud alongside one another, much as we see them today. However, when careful measurements of the lunar orbit were made, they showed that it was not steady but was changing with time. So a new theory arose. This theory held that the Moon formed independently of Earth elsewhere in the solar system and was captured by Earth’s gravity as it crossed Earth’s orbit. If our Moon were formed elsewhere, such an alien moon would have a different geological history and structure than Earth, reflecting the region of the solar system in which it was formed. The Earth capture theory fell out of favor when it was found that the Moon’s geology and planetary characteristics closely resembled Earth’s. However, in the 1980s, it was revived with the realization that some meteorites that had struck the Earth were of lunar origin and differed slightly from terrestrial rocks.
According to paragraph 1, in the 1980s, new knowledge about the composition of meteorites that originated on the Moon led to which of the following?
Factual Information Questions事实信息题
AConfirmation that the Moon formed at the same time and in the same way as Earth
BRecognition of the similarities in geology and planetary characteristics between the Moon and Earth
CRenewed belief in the theory that the Moon formed elsewhere in the solar system
DDevelopment of an entirely new theory about the origins of the Moon
3
Towards the end of the twentieth century, a more advanced and informed theory developed, postulating that the Moon was born following a cataclysmic collision between early Earth and another planetary object with an irregular orbit that crossed Earth’s orbit. This collision would have occurred around 4.5 billion years ago, when the smaller early (or “proto-“) Earth was still largely molten and not quite yet solidified. The colliding object would have been roughly the size of Mars and has been given the name Theia. The collision was so cataclysmic that it knocked Earth off its axis, resulting in the current 23.5 tilt we see today. The tilt, now stabilized by the Moon, gives us our seasons during each orbit of the Sun. The impact was so catastrophic that the proto-Earth fractured and any early atmosphere was lost, with Theia being largely destroyed. The majority of the pulverized Theia mixed with Earth, and the remaining ejected debris formed a hot disc of vapor and material around the planet, much like the rings of Saturn. Then, over many centuries, some of the orbiting debris fell to Earth and mixed with the cooling surface, while the remainder coalesced to form the orbiting Moon. This created a Moon with a similar geological composition to that of Earth, with Theia’s unique characteristics being completely obliterated in the process.
The word “fractured” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aheated up
Bmoved to a different position
Cwas transformed
Dbroke into pieces
4
Towards the end of the twentieth century, a more advanced and informed theory developed, postulating that the Moon was born following a cataclysmic collision between early Earth and another planetary object with an irregular orbit that crossed Earth’s orbit. This collision would have occurred around 4.5 billion years ago, when the smaller early (or “proto-“) Earth was still largely molten and not quite yet solidified. The colliding object would have been roughly the size of Mars and has been given the name Theia. The collision was so cataclysmic that it knocked Earth off its axis, resulting in the current 23.5 tilt we see today. The tilt, now stabilized by the Moon, gives us our seasons during each orbit of the Sun. The impact was so catastrophic that the proto-Earth fractured and any early atmosphere was lost, with Theia being largely destroyed. The majority of the pulverized Theia mixed with Earth, and the remaining ejected debris formed a hot disc of vapor and material around the planet, much like the rings of Saturn. Then, over many centuries, some of the orbiting debris fell to Earth and mixed with the cooling surface, while the remainder coalesced to form the orbiting Moon. This created a Moon with a similar geological composition to that of Earth, with Theia’s unique characteristics being completely obliterated in the process.
According to paragraph 2. which of the following is a key part of the late twentieth-century theory about a collision between Earth and a large planetary object called Theia?
Factual Information Questions事实信息题
AThe collision occurred when the proto-Earth was about the size Mars is today.
BThe collision caused the tilt of the Moon to stabilize.
CThe collision gave Earth its early atmosphere
DThe collision mostly destroyed Theia and mixed most of its material with that of Earth.
5
Towards the end of the twentieth century, a more advanced and informed theory developed, postulating that the Moon was born following a cataclysmic collision between early Earth and another planetary object with an irregular orbit that crossed Earth’s orbit. This collision would have occurred around 4.5 billion years ago, when the smaller early (or “proto-“) Earth was still largely molten and not quite yet solidified. The colliding object would have been roughly the size of Mars and has been given the name Theia. The collision was so cataclysmic that it knocked Earth off its axis, resulting in the current 23.5 tilt we see today. The tilt, now stabilized by the Moon, gives us our seasons during each orbit of the Sun. The impact was so catastrophic that the proto-Earth fractured and any early atmosphere was lost, with Theia being largely destroyed. The majority of the pulverized Theia mixed with Earth, and the remaining ejected debris formed a hot disc of vapor and material around the planet, much like the rings of Saturn. Then, over many centuries, some of the orbiting debris fell to Earth and mixed with the cooling surface, while the remainder coalesced to form the orbiting Moon. This created a Moon with a similar geological composition to that of Earth, with Theia’s unique characteristics being completely obliterated in the process.
According to the theory described in paragraph 2, all of the following happened to the materials ejected by the collision EXCEPT:
Negative Factual Information Questions否定事实信息题
AThe materials formed a disk around Earth
BSome of the materials were vaporized by Earth’s atmosphere.
CSome of the debris fell to Earth over many centuries.
DMuch of the debris slowly came together to form the Moon.
6
This theory has some limitations. While it requires the total destruction of Theia, it also requires that the orbiting ejected material would have to remain very hot for a long time to allow sufficient mixing to occur. It is very difficult to achieve this level of heating from a head-on collision. Thus, a more recent theory suggests that the collision was not head-on but was more like a high-speed glancing blow. This sort of collision creates the heat required, and, if this theory is correct, then, somewhere in the solar system a remnant of Theia may still survive.
According to paragraph 3, what is the main problem with the collision theory presented in the previous paragraph?
Factual Information Questions事实信息题
AEarth could not have withstood the level of heat for the length of time described without being destroyed.
BEven the total destruction of Theia would not have created enough ejected material to create the Moon.
CA direct collision would not have created enough heat for extensive mixing of materials from Theia and Earth
DA remnant of Theia should have survived and been detected somewhere in the solar system if the theory were true
7
The collision with Theia left Earth with a heavy molten-iron, radioactive core, giving it the ability to generate heat and a protective magnetic field. The Moon was left with only a small molten-iron core and a very weak magnetic field. Since then, the dynamic interaction between the liquid portion of Earth’s core and its hard outer layer, the mantle, ensures that Earth’s surface has been in continuous flux and the surface is always being subsumed or reformed through various geological processes somewhere in the world. While orbiting debris would have rained down onto the surface of the cooling Earth and Moon for millennia, there is scant evidence of this debris on Earth, as it has been lost in the continual geological reshaping and later weathering of the surface. Remarkably, on the Moon, a large proportion of the original surface remains just as it formed those many billions of years ago. While the surface is not flat and has undergone some volcanism of its own, there are plenty of valleys and mountains left over from this era. While moonquakes do occur, they do not alter the surface and are small-more like tremors. The Moon’s surface therefore provides a record not only of the Moon of billions of years ago, but of all the impacts that have rained down on its surface throughout its lifetime.
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
AEver since, Earth’s surface has been continuously changed by geological processes due to the interaction between Earth’s core and mantle.
BAfter that, liquid from Earth’s core has been in continuous flux and always rises to Earth’s surface somewhere in the world
CVarious geological processes around the world ensure that a portion of Earth’s core remains liquid while its outer layer remains hard
DSince then, Earth has been composed of a liquid core and a hard outer layer called the mantle, both in continuous flux.
8
The collision with Theia left Earth with a heavy molten-iron, radioactive core, giving it the ability to generate heat and a protective magnetic field. The Moon was left with only a small molten-iron core and a very weak magnetic field. Since then, the dynamic interaction between the liquid portion of Earth’s core and its hard outer layer, the mantle, ensures that Earth’s surface has been in continuous flux and the surface is always being subsumed or reformed through various geological processes somewhere in the world. While orbiting debris would have rained down onto the surface of the cooling Earth and Moon for millennia, there is scant evidence of this debris on Earth, as it has been lost in the continual geological reshaping and later weathering of the surface. Remarkably, on the Moon, a large proportion of the original surface remains just as it formed those many billions of years ago. While the surface is not flat and has undergone some volcanism of its own, there are plenty of valleys and mountains left over from this era. While moonquakes do occur, they do not alter the surface and are small-more like tremors. The Moon’s surface therefore provides a record not only of the Moon of billions of years ago, but of all the impacts that have rained down on its surface throughout its lifetime.
In paragraph 4, why does the author contrast the Moon’s relatively little geological activity with Earth’s continual geological activity?
Factual Information Questions事实信息题
ATo explain why the surface of the Moon provides evidence of its history that has been lost on Earth’s surface
BTo highlight the fact that the Moon has experienced some volcanic activity of its own
CTo suggest that the Moon is many billions of years older than previously thought
DTo argue that tremors and volcanism on the Moon result from a different cause than those on Earth
9
One of the earliest scientific theories about the Moon’s origin postulated that Earth and its moon formed out of a dust cloud alongside one another, much as we see them today. ⬛However, when careful measurements of the lunar orbit were made, they showed that it was not steady but was changing with time. ⬛So a new theory arose. This theory held that the Moon formed independently of Earth elsewhere in the solar system and was captured by Earth’s gravity as it crossed Earth’s orbit. ⬛If our Moon were formed elsewhere, such an alien moon would have a different geological history and structure than Earth, reflecting the region of the solar system in which it was formed. ⬛The Earth capture theory fell out of favor when it was found that the Moon’s geology and planetary characteristics closely resembled Earth’s. However, in the 1980s, it was revived with the realization that some meteorites that had struck the Earth were of lunar origin and differed slightly from terrestrial rocks.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Some scientists have theorized that Earth’s moon originally formed in orbit around VenusInsert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Scientific theories about the origins of the Moon have changed as new information has been discovered.
Prose Summary Questions概要小结题
Select 3 answers
ABased on changes in the lunar orbit, early scientists believed that the Moon likely formed gradually from a dust cloud near Earth and only solidified relatively recently
BIn the late twentieth century, it was suggested that a Mars-sized object collided with Earth and that that collision led to both the Moon’s formation and Earth’s tilt on its axis
CThe theory involving a collision with Theia is too limited to account for the amount of material that would have had to be ejected into Earth’s orbit to create the Moon.
DPrevious theories included that Earth and Moon formed alongside one another and that the Moon was formed elsewhere and captured by Earth’s gravity.
EA collision would account for several features of Earth and the Moon, but, if there was a collision, it is more likely that it was a glancing blow than that it was a head-on collision.
FEarth’s protective magnetic field has ensured that very little orbiting debris has rained down onto the surface of Earth, so most of the debris rained down on the Moon.
