『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 16 Passage 3阅读练习：Paragraph 4 mentions which of the following as a reason why terrestrial planets are dense?真题题目及答案解析，TPO/Official 16 Passage 3阅读原文范文音频翻译

托福TPO/Official 16 Passage 3阅读原文Paragraph 4 mentions which of the following as a reason why terrestrial planets are dense?题目答案及解析-新东方托福官方网校手机版

太阳是一个巨大的旋转系统的中心，这个旋转系统由九大行星、它们的卫星和无数的小天体组成，这些小天体包括小行星、彗星和流星体。

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.

据估计，太阳系质量的99.85%包含在太阳中，而其余的0.15%则由行星共同组成。

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.

这些行星，按照它们与太阳的距离，分别是水星、金星、地球、火星、木星、土星、天王星、海王星和冥王星。

The planets, in order of their distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.

在太阳引力的控制下，每颗行星都保持着一个椭圆形的轨道，并朝着同一个方向运行。

Under the control of the Sun’s gravitational force, each planet maintains an elliptical orbit and all of them travel in the same direction.

我们太阳系中的行星分为两类：类地行星（水星、金星、地球和火星）和类木行星（木星、土星、天王星和海王星）。

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).

冥王星不属于这两类，因为它离地球太远，且体积小，这让这颗行星的真正性质仍是一个谜。

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.

类地行星和类木行星之间最明显的区别是它们的大小。

The most obvious difference between the terrestrial and the Jovian planets is their size.

地球是最大的类地行星，其直径只有最小的类木行星海王星直径的四分之一，其质量只有海王星的十七分之一。

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.

因此，类木行星通常被称为巨行星。

Hence, the Jovian planets are often called giants.

同样，由于它们的相对位置，四颗类木行星被称为外行星，而类地行星被称为内行星。

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.

这些行星的位置和它们的大小之间似乎有某种相关性。

There appears to be a correlation between the positions of these planets and their sizes.

在密度和组成方面，这两个群体有显著的不同。

Other dimensions along which the two groups differ markedly are density and composition.

类地行星的密度平均约为水密度的5倍，而类木行星的密度平均只有水密度的1.5倍。

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.

土星是外行星之一，它的密度只有水的0.7，这意味着土星会漂浮在水中。

One of the outer planets, Saturn, has a density of only 0.7 that of water, which means that Saturn would float in water.

行星组成的变化是造成密度差异的主要原因。

Variations in the composition of the planets are largely responsible for the density differences.

构成这两组行星的物质根据它们的熔点分为三组：气体、岩石和冰。

The substances that make up both groups of planets are divided into three groups—gases, rocks, and ices—based on their melting points.

类地行星大部分是岩石：密集的岩石和金属材料，少量的气体。

The terrestrial planets are mostly rocks: dense rocky and metallic material, with minor amounts of gases.

另一方面，类木行星含有大量的氢气和氦气，以及不同数量的冰：主要是水、氨和甲烷冰。

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.

类木行星有非常厚的大气层，由不同数量的氢、氦、甲烷和氨组成。

The Jovian planets have very thick atmospheres consisting of varying amounts of hydrogen, helium, methane, and ammonia.

相比之下，类地行星的大气层充其量也只能算是稀薄。

By comparison, the terrestrial planets have meager atmospheres at best.

行星保持大气的能力取决于它的温度和质量。

A planet’s ability to retain an atmosphere depends on its temperature and mass.

简单地说，如果气体分子达到逃逸速度，它就能从行星上“蒸发”。

Simply stated, a gas molecule can “evaporate” from a planet if it reaches a speed known as the escape velocity.

对地球来说，这个速度是11千米每秒。

For Earth, this velocity is 11 kilometers per second.

任何物质，包括火箭，必须达到这个速度才能离开地球进入太空。

Any material, including a rocket, must reach this speed before it can leave Earth and go into space.

由于类木行星的质量更大，因此表面的重力也更大，所以它们的逃逸速度（21-60公里/秒）比类地行星要快。

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.

因此，气体更难从这些气体中“蒸发”出来。

Consequently, it is more difficult for gases to “evaporate” from them.

此外，由于气体的分子运动依赖于温度，在类木行星的低温下，即使是最轻的气体也不可能获得逃逸所需的速度。

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.

另一方面，一个相对温暖、表面引力较小的天体，比如地球的卫星，就连最重的气体也无法容纳，因此缺少大气层。

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.

稍大一些的类地行星，如地球、金星和火星，保留了一些像二氧化碳这样的重气体，但即使是它们的大气层，也只占它们总质量的极小部分。

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.

我们太阳系的有序特性使大多数天文学家得出这样的结论：这些行星基本上与太阳形成于同一时间，由同一种物质构成。

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.

据推测，所有行星都是由尘埃和气体组成的原始云团凝聚而成，原始云团与木星的组成有些相似。

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.

然而，与木星不同的是，如今的类地行星几乎没有轻气体和冰。

However, unlike Jupiter, the terrestrial planets today are nearly void of light gases and ices.

对此的解释可能是，类地行星曾经体积更大，构成材料更丰富，但最终因为这些天体与太阳的距离相对较近而消失了，这意味着它们的温度相对较高。

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.

According to the passage, each of the following statements comparing terrestrial planets with Jovian planets is true EXCEPT:

The word “markedly” in the passage is closest in meaning to

Paragraph 4 mentions which of the following as a reason why terrestrial planets are dense?

Paragraph 4 supports each of the following statements about Saturn EXCEPT:

The word “meager” in the passage is closest in meaning to

According to paragraph 5, which of the following statements is true of both Jovian and terrestrial planets?

According to paragraph 5, what is a major reason that Jovian planets have much thicker atmospheres than terrestrial planets do?

Paragraph 5 supports which of the following statements about the ability of planets to retain gases?

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

The word “eventually” in the passage is closest in meaning to

According to paragraph 6, what is a possible explanation for the lack of light gases and ices on terrestrial planets?

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? Click on a square  to add the sentence to the passage.

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.

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.  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.