Download 托福tpo - 小马过河

托福 tpo 历史学复习：太阳系中的行星
小马过河为大家准备了“托福 tpo 历史学复习：太阳系中的行星”
，供各位备考托福的
考生们参考使用，来提高自己的托福成绩！免费咨询电话：400-0123-267
Planets in Our Solar System
The Sun is the hub of a huge rotating system consisting of nine planets, their satellites,
and numerous small bodies, including asteroids, comets, and meteoroids. An estimated 99.85 percent
of the mass of our solar system is contained within the Sun, while the planets collectively
make up most of the remaining 0.15 percent. The planets, in order of their distance from the
Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Under the
control of the Sun's gravitational force, each planet maintains an elliptical orbit and all
of them travel in the same direction.
The planets in our solar system fall into two groups: the terrestrial (Earth-like) planets
(Mercury, Venus, Earth, and Mars) and the Jovian (Jupiter-like) planets (Jupiter, Saturn, Uranus,
and Neptune). Pluto is not included in either category, because its great distance from Earth
and its small size make this planet's true nature a mystery.
The most obvious difference between the terrestrial and the Jovian planets is their size.
The largest terrestrial planet, Earth has a diameter only one quarter as great as the diameter
of the smallest Jovian planet, Neptune, and its mass is only one seventeenth as great. Hence,
the Jovian planets are often called giants. Also, because of their relative locations, the four
Jovian planets are known as the outer planets, while the terrestrial planets are known as the
inner planets. There appears to be a correlation between the positions of these planets and
their sizes.
Other dimensions along which the two groups differ markedly are density and composition.
The densities of the terrestrial planets average about 5 times the density of water, whereas
the Jovian planets have densities that average only 1.5 times the density of water. One of the
outer planets, Saturn, has a density of only 0.7 that of water, which means that Saturn would
float in water. Variations in the composition of the planets are largely responsible for the
density differences. The substances that make up both groups of planets are divided into three
groups—gases, rocks, and ices—based on their melting points. The terrestrial planets are mostly
rocks: dense rocky and metallic material, with minor amounts of gases. The Jovian planets, on
the other hand, contain a large percentage of the gases hydrogen and helium, with varying amounts
of ices: mostly water, ammonia, and methane ices.
全国免费咨询电话：400-0123-267
The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen,
helium, methane, and ammonia. By comparison, the terrestrial planets have meager atmospheres
at best. A planet's ability to retain an atmosphere depends on its temperature and mass. Simply
stated, a gas molecule can "evaporate" from a planet if it reaches a speed known as the escape
velocity. For Earth, this velocity is 11 kilometers per second. Any material, including a rocket,
must reach this speed before it can leave Earth and go into space. The Jovian planets, because
of their greater masses and thus higher surface gravities, have higher escape velocities (21-60
kilometers per second) than the terrestrial planets. Consequently, it is more difficult for
gases to "evaporate" from them. Also, because the molecular motion of a gas depends on temperature,
at the low temperatures of the Jovian planets even the lightest gases are unlikely to acquire
the speed needed to escape. On the other hand, a comparatively warm body with a small surface
gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an atmosphere.
The slightly larger terrestrial planets Earth, Venus, and Mars retain some heavy gases like
carbon dioxide, but even their atmospheres make up only an infinitesimally small portion of
their total mass.
The orderly nature of our solar system leads most astronomers to conclude that the planets
formed at essentially the same time and from the same material as the Sun. It is hypothesized
that the primordial cloud of dust and gas from which all the planets are thought to have condensed
had a composition somewhat similar to that of Jupiter. However, unlike Jupiter, the terrestrial
planets today are nearly void of light gases and ices. The explanation may be that the terrestrial
planets were once much larger and richer in these materials but eventually lost them because
of these bodies' relative closeness to the Sun, which meant that their temperatures were relatively
high.
1. According to the passage, each of the following statements comparing terrestrial planets
with Jovian planets is true EXCEPT: (4)
○Terrestrial planets are closer to the Sun than Jovian planets.
○Terrestrial planets have smaller diameters than Jovian planets.
○Terrestrial planets have smaller masses than Jovian planets.
○Terrestrial planets travel in a different direction than Jovian planets do.
Paragraph 4: Other dimensions along which the two groups differ markedly are density and
composition. The densities of the terrestrial planets average about 5 times the density of water,
whereas the Jovian planets have densities that average only 1.5 times the density of water.
One of the outer planets, Saturn, has a density of only 0.7 that of water, which means that
Saturn would float in water. Variations in the composition of the planets are largely responsible
全国免费咨询电话：400-0123-267
for the density differences. The substances that make up both groups of planets are divided
into three groups—gases, rocks, and ices—based on their melting points. The terrestrial planets
are mostly rocks: dense rocky and metallic material, with minor amounts of gases. The Jovian
planets, on the other hand, contain a large percentage of the gases hydrogen and helium, with
varying amounts of ices: mostly water, ammonia, and methane ices.
2. The word markedly in the passage is closest in meaning to (4)
○Essentially
○Typically
○Consistently
○noticeably
3. Paragraph 4 mentions which of the following as a reason why terrestrial planets are
dense?(2)
○They are made up of three groups of substances.
○They are composed mainly of rocky and metallic materials.
○They contain more ice than Jovian planets.
○They contain relatively small amounts of water.
4. Paragraph 4 supports each of the following statements about Saturn EXCEPT: (2)
○It is less dense than any of the terrestrial planets.
○It contains no rocky material.
○It contains ices.
○It contains a large percentage of gases.
Paragraph 5: The Jovian planets have very thick atmospheres consisting of varying amounts
of hydrogen, helium, methane, and ammonia. By comparison, the terrestrial planets have meager
atmospheres at best. A planet's ability to retain an atmosphere depends on its temperature and
mass. Simply stated, a gas molecule can "evaporate" from a planet if it reaches a speed known
as the escape velocity. For Earth, this velocity is 11 kilometers per second. Any material,
全国免费咨询电话：400-0123-267
including a rocket, must reach this speed before it can leave Earth and go into space. The Jovian
planets, because of their greater masses and thus higher surface gravities, have higher escape
velocities (21-60 kilometers per second) than the terrestrial planets. Consequently, it is more
difficult for gases to "evaporate" from them. Also, because the molecular motion of a gas depends
on temperature, at the low temperatures of the Jovian planets even the lightest gases are unlikely
to acquire the speed needed to escape. On the other hand, a comparatively warm body with a small
surface gravity, like Earth's moon, is unable to hold even the heaviest gas and thus lacks an
atmosphere. The slightly larger terrestrial planets Earth, Venus, and Mars retain some heavy
gases like carbon dioxide, but even their atmospheres make up only an infinitesimally small
portion of their total mass.
5. The word meager in the passage is closest in meaning to (2)
○rich
○thin
○unique
○complex
6. According to paragraph 5, which of the following statements is true of both Jovian and
terrestrial planets? (3)
○ The thicker the atmosphere, the smaller the planet’s mass
○ The more varied the gases in the atmosphere, the higher the temperature
○ The higher the surface gravity, the higher the escape velocity
○ The less the atmosphere contributes to the total mass, the lower the temperature
7. According to paragraph 5, what is a major reason that Jovian planets have much thicker
atmospheres than terrestrial planets do? (2)
○ Jovian planets have lower surface gravities
○ Jovian planets have lower temperatures
○ Jovian planets have lower escape velocities
○ Jovian planets’ gas molecules have higher average speeds
全国免费咨询电话：400-0123-267
8. Paragraph 5 supports which of the following statements about the ability of planets to
retain gases?(2)
○More-massive planets are less able to retain gases than less-massive ones.
○Planets are more likely to retain heavy gases than light gases.
○Jovian planets are unlikely to retain the lightest gases.
○Only terrestrial planets have been able to retain carbon dioxide.
Paragraph 6: The orderly nature of our solar system leads most astronomers to conclude that
the planets formed at essentially the same time and from the same material as the Sun. It is
hypothesized that the primordial cloud of dust and gas from which all the planets are thought
to have condensed had a composition somewhat similar to that of Jupiter. However, unlike Jupiter,
the terrestrial planets today are nearly void of light gases and ices. The explanation may be
that the terrestrial planets were once much larger and richer in these materials but eventually
lost them because of these bodies' relative closeness to the Sun, which meant that their
temperatures were relatively high.
9. In calling the cloud of gas and dust from which the Sun and all the planets are thought
to have condensed "primordial,' the author means that the cloud was (3)
○immense in size
○composed of similar particles
○present at the very beginning of our solar system's formation
○created from a great variety of different materials
10. The word eventually in the passage is closest in meaning to (1)
○over time
○long ago
○simply
○certainly
全国免费咨询电话：400-0123-267
11. According to paragraph 6, what is a possible explanation for the lack of light gases
and ices on terrestrial planets? (1)
○The location of terrestrial planets caused them to lose some of the materials they once
contained.
○Terrestrial planets were formed much later than Jovian planets.
○The composition of terrestrial planets was different from that of Jupiter.
○Terrestrial planets were formed out of different material than the Sun was.
Paragraph 4: Other dimensions along which the two groups differ markedly are density and
composition. The densities of the terrestrial planets average about 5 times the density of water,
whereas the Jovian planets have densities that average only 1.5 times the density of water.
One of the outer planets, Saturn, has a density of only 0.7 that of water, which means that
Saturn would float in water. Variations in the composition of the planets are largely responsible
for the density differences. ■The substances that make up both groups of planets are divided
into three groups—gases, rocks, and ices—based on their melting points. ■The terrestrial
planets are mostly rocks: dense rocky and metallic material, with minor amounts of gases. ■The
Jovian planets, on the other hand, contain a large percentage of the gases hydrogen and helium,
with varying amounts of ices: mostly water, ammonia, and methane ices. ■
12. Look at the four squares [■] that indicate where the following sentence could be added
to the passage.
This explains their relatively low densities.
Where would the sentence best fit?(4)
10. Directions: From the seven answer choices below, select the two phrases that correctly
characterize the terrestrial planets and the three phrases that correctly characterize the Jovian
planets. Drag each phrase you select into the appropriate column of the table. Two of the phrases
will NOT be used. This question is worth 3 points.
terrestrial planetsJovian planets
●(1)
●(4)●(3)
全国免费咨询电话：400-0123-267
●(6)
● (7)
Answer Choices
○Have relatively small sizes
○Are grouped in the same category as Pluto
○Contain relatively high proportions of ices
○Have relatively high temperatures
○Have densities that are generally lower than the density of water
○Have relatively high escape velocities
○Have a composition closer to that of the cloud from which they condensed terrestrial
参考答案：
1. ○4
2. ○4
3. ○2
4. ○2
5. ○2
6. ○3
7. ○2
8.○2
9. ○3
10. ○1
全国免费咨询电话：400-0123-267
11. ○1
12. ○4
13. ○1,4 ○3, 6,7
参考译文：太阳系中的行星
太阳是这个由九大行星构成的巨大公转系统的核心，该系统中还有九大行星的卫星，和大量的小星体，
包括小行星，彗星，和陨星体。我们所在的太阳系中，差不多百分之 99.85 的质量是太阳，与此同时，行
星们共同组成了剩下的百分之 0.15 的大部分质量。这些行星们依据他们距离太阳的远近依次排列为：水星，
金星，地球，火星，木星，土星，天王星，海王星，和冥王星。在太阳的引力作用下，每个行星都保持着
椭圆形的轨道和相同的公转方向。
9 大行星分为两部分，一部分叫类地行星(和地球差不多)其中有(水星，金星，地球和火星)，另一类
叫类木行星(和木星差不多)包括(木星，土星，天王星，海王星)，冥王星不属于这两个中的任何一个，因
为它距离地球实在太远而它的体型又太小，所以无法得知冥王星的真实形态。
类地行星和类木行星最为明显的差别就是他们的体型。比如最大的类地行星地球的直径也不过是最小
的类木行星海王星的四分之一大，而地球的质量更是只有可怜的 17 分之一。因此，类木行星通常又被称为
巨行星。因为这四颗类木行星相互之间与地球的位置，他们也被我们称为外环行星，同时类地行星则被称
作“内环行星”。这也是行星的位置与行星的尺寸所展现出的一些相关性。
两组行星另一些方面的不同中比较明显的就是密度和构成成分了。类地行星的密度的平均值大概是水
的密度的五倍，而类木行星的密度大概只有水的密度的 1.5 倍。外环行星中的土星的密度只有水的 0,7 倍，
也就是说，土星是可以浮在水面上的。行星的构成成分的组合也在很大程度上导致了密度的不同。两种行
星都存在的物质根据他们的融点可以划分为三种---气体，岩石和冰。类地行星大多数为岩石，致密的石块
和金属性质的材料，以及较为稀薄的气体。类木行星，恰恰相反，包含较大比例的气态氢和氦，以及各种
形态的冰，多数是水，氨和甲烷。
类木行星有非常致密的大气，这种大气是由大量的氢和氦，甲烷和氨所组成的。对比而言，类地行星
的大气则要稀薄得多。一个行星抓住大气的能力取决于它的温度和质量。简单来说，如果气体的速度达到
了我们所知道的“逃逸速度”，那么一个气体分子可以从行星上“蒸发”。对于地球来讲，这个逃逸速度
是每秒 11 千米。任何物质，包括火箭，必须要在离开地球之前达到这个速度才能进入外层空间。由于类木
行星的质量巨大并因此产生了巨大的表面重力，类木行星的逃逸速度要比类地行星高得多(21—60 千米每
秒)。结果就是气体更加的不容易从类木行星的表面“蒸发”。同理，因为气体分子的运动能力同时还取决
于温度，所以在类木行星这样的低温环境下，即使是最轻的气体也无法达到所需要的逃逸速度。而从另一
个角度讲，一个相对较热的物体再加上一个较小的表面重力，比如月亮，就无法留住哪怕是最重的气体，
也因此没有大气层。这些稍微大一点的类地行星，比如地球，金星和火星保留住了一部分较重的气体比如
二氧化碳之类的，但是即使是这样他们的大气构成也只有保留住相对于他们的质量而言极小比例的一部分
大气。
全国免费咨询电话：400-0123-267
我们太阳系比较有序的外部环境使大部分包括行星在内的天体基本上是在同一时间，并有同样的类似
太阳的构成作为基本元素构成的。有一个假说认为在天地初开的时候，像木星那样尘埃和气体的聚合与压
缩是所有行星产生的最初形态。然而，和木星不同的是，类地行星现在的气体和冰已经很少了。关于这个
的解释是，也许类地行星在物质的构成上要远远比类木行星丰富和多样，而因为他们的位置太靠近太阳而
使相对温度比较高而最终丢失了这些物质。
来源于：小马过河
小马过河资料下载频道，欢迎您来下载！
全国免费咨询电话：400-0123-267