『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 41 Passage 2阅读练习：The phrase “mechanism for” in the passage is closest in meaning to真题题目及答案解析，TPO/Official 41 Passage 2阅读原文范文音频翻译

托福TPO/Official 41 Passage 2阅读原文The phrase “mechanism for” in the passage is closest in meaning to题目答案及解析-新东方托福官方网校手机版

地球的海洋中有丰富的水，但在相对稀薄的大气层中只有很少的二氧化碳。

Earth has abundant water in its oceans but very little carbon dioxide in its relatively thin atmosphere.

相比之下，金星非常干燥，它厚厚的大气层主要由二氧化碳构成。

By contrast, Venus is very dry and its thick atmosphere is mostly carbon dioxide.

金星和地球最初的大气层中至少有一部分是由火山喷出或排出的气体形成的。

The original atmospheres of both Venus and Earth were derived at least in part from gases spewed forth, or outgassed, by volcanoes.

现在地球上的火山，如圣海伦斯火山，所喷发出的气体主要是水蒸气、二氧化碳和二氧化硫。

The gases that emanate from present-day volcanoes on Earth, such as Mount Saint Helens, are predominantly water vapor, carbon dioxide, and sulfur dioxide.

因此，这些气体应该是金星和地球原始大气层中的重要组成部分。

These gases should therefore have been important parts of the original atmospheres of both Venus and Earth.

这两颗行星上大部分的水也被认为是来自于彗星这种太阳系外形成的冰体的撞击。

Much of the water on both planets is also thought to have come from impacts from comets, icy bodies formed in the outer solar system.

事实上，水可能曾经主宰了金星的大气层。

In fact, water probably once dominated the Venusian atmosphere.

金星和地球在大小和质量上都很相似，所以金星上的火山释放的水蒸气很可能和地球上的一样多，而且撞击这两个行星表面的彗星数量也差不多。

Venus and Earth are similar in size and mass, so Venusian volcanoes may well have outgassed as much water vapor as on Earth, and both planets would have had about the same number of comets strike their surfaces.

有关于恒星如何演化的研究表明，早期太阳的亮度只有现在的70%，所以金星早期大气的温度要比现在低一些。

Studies of how stars evolve suggest that the early Sun was only about 70 percent as luminous as it is now, so the temperature in Venus’ early atmosphere must have been quite a bit lower.

因此水蒸气可以液化并在金星上形成海洋。

Thus water vapor would have been able to liquefy and form oceans on Venus.

但是如果水蒸气和二氧化碳曾经在地球和金星的大气层中如此普遍，那么曾经地球中大量的二氧化碳变成了什么呢?

But if water vapor and carbon dioxide were once so common in the atmospheres of both Earth and Venus, what became of Earth’s carbon dioxide?

第一个问题的答案是,地球上还是有大量的二氧化碳存在的,但是现在它们大部分并不是以气体的形式存在的，而是溶解在了海洋中或产生化学反应形成了碳酸盐岩石,例如海洋中的石灰石和大理石。

The answer to the first question is that carbon dioxide is still found in abundance on Earth, but now, instead of being in the form of atmospheric carbon dioxide, it is either dissolved in the oceans or chemically bound into carbonate rocks, such as the limestone and marble that formed in the oceans.

如果地球变得和金星一样热，那么地球上大部分的二氧化碳就会从海洋中被蒸发出来，从地壳中烘烤出来。

If Earth became as hot as Venus, much of its carbon dioxide would be boiled out of the oceans and baked out of the crust.

我们的星球很快就会形成一层厚厚的、令人窒息的二氧化碳大气层，就像金星的大气层一样。

Our planet would soon develop a thick, oppressive carbon dioxide atmosphere much like that of Venus.

要回答金星缺少水的问题，我们必须回溯金星的早期历史。

To answer the question about Venus’ lack of water, we must return to the early history of the planet.

就像今天的地球一样，金星的海洋将大气中的二氧化碳溶解在海中，并将其与碳酸盐岩结合，从而限制了二氧化碳的总量。

Just as on present-day Earth, the oceans of Venus limited the amount of atmospheric carbon dioxide by dissolving it in the oceans and binding it up in carbonate rocks.

但是，由于金星相比地球来说离太阳更近，金星上丰富的液态水被蒸发，形成了厚厚的水蒸气云。

But being closer to the Sun than Earth is, enough of the liquid water on Venus would have vaporized to create a thick cover of water vapor clouds.

由于水蒸气是一种温室气体，这种潮湿的大气——也许比地球现在的大气密度大，但比今天环绕金星的大气密度要小得多——能够有效地将从太阳吸收的热量困住。

Since water vapor is a greenhouse gas, this humid atmosphere—perhaps denser than Earth’s present-day atmosphere, but far less dense than the atmosphere that envelops Venus today—would have efficiently trapped heat from the Sun.

起初，这对金星的海洋几乎没有什么影响。

At first, this would have had little effect on the oceans of Venus.

尽管温度会上升到100摄氏度以上，也就是地球海平面上水的沸点，但是水蒸气所增加的大气压能够使金星海洋中的水保持液态。

Although the temperature would have climbed above 100° C, the boiling point of water at sea level on Earth, the added atmospheric pressure from water vapor would have kept the water in Venus’ oceans in the liquid state.

这种湿热的状态可能已经持续了几亿年。

This hot and humid state of affairs may have persisted for several hundred million years.

但随着时间的推移，太阳的能量输出逐渐增加，其表面温度最终上升到374摄氏度以上。

But as the Sun’s energy output slowly increased over time, the temperature at the surface would eventually have risen above 374°C.

在这个温度之上，无论大气压如何，金星上的海洋都会开始蒸发，大气中增加的水蒸气会进一步增加温室效应。

Above this temperature, no matter what the atmospheric pressure, Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect.

这将使温度更高，从而导致海洋蒸发得更快，产生更多的水蒸气。

This would have made the temperature even higher and caused the oceans to evaporate faster, producing more water vapor.

这反过来又会进一步加剧温室效应，使气温进一步攀升。

That, in turn, would have further intensified the greenhouse effect and made the temperature climb higher still.

一旦金星上的海洋消失，从大气中清除二氧化碳的机制也就随之消失了。

Once Venus’ oceans disappeared, so did the mechanism for removing carbon dioxide from the atmosphere.

由于没有海洋来溶解它，释放出的二氧化碳开始便在大气中累积，进一步加剧温室效应。

With no oceans to dissolve it, outgassed carbon dioxide began to accumulate in the atmosphere, intensifying the greenhouse effect even more.

温度最终升高到足以“烘烤出”任何被困在碳酸盐岩中的二氧化碳。

Temperatures eventually became high enough to “bake out” any carbon dioxide that was trapped in carbonate rocks.

这些释放出来的二氧化碳形成了今天金星厚厚的大气层。

This liberated carbon dioxide formed the thick atmosphere of present-day Venus.

随着时间的推移，上升的温度趋于稳定，太阳紫外线辐射已经将大气中的水蒸气分子分解成了氢和氧。

Over time, the rising temperatures would have leveled off, solar ultraviolet radiation having broken down atmospheric water vapor molecules into hydrogen and oxygen.

随着所有水蒸气的消失，温室效应将不再加速。

With all the water vapor gone, the greenhouse effect would no longer have accelerated.

According to paragraph 1, in what major respect are Venus and Earth different from each other?

Why does the author mention “present-day volcanoes on Earth”?

According to paragraph 2, what is one reason for thinking that at one time, there were significant amounts of water on Venus?

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

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.

According to paragraph 4, what is one factor that kept the amount of carbon dioxide in the atmosphere of early Venus relatively low?

The phrase “mechanism for” in the passage is closest in meaning to

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

According to paragraph 5, what happens when temperatures rise above 374ºC?

According to paragraph 6, extremely high temperatures increased the amount of carbon dioxide in Venus’ atmosphere by

The passage supports the idea that the basic reason that Venus and Earth are now so different from each other is that

Look at the four squares  that indicate where the following sentence could be added to the passage. This cycle of rising temperatures following an increase in greenhouse gases is known as the runaway greenhouse effect.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: Select from the seven phrases below the 2 phrases that correctly characterize early Venus and the 3 phrases that correctly characterize present-day Venus. 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.

Climate of Venus Earth has abundant water in its oceans but very little carbon dioxide in its relatively thin atmosphere. By contrast, Venus is very dry and its thick atmosphere is mostly carbon dioxide. The original atmospheres of both Venus and Earth were derived at least in part from gases spewed forth, or outgassed, by volcanoes. The gases that emanate from present-day volcanoes on Earth, such as Mount Saint Helens, are predominantly water vapor, carbon dioxide, and sulfur dioxide. These gases should therefore have been important parts of the original atmospheres of both Venus and Earth. Much of the water on both planets is also thought to have come from impacts from comets, icy bodies formed in the outer solar system. In fact, water probably once dominated the Venusian atmosphere. Venus and Earth are similar in size and mass, so Venusian volcanoes may well have outgassed as much water vapor as on Earth, and both planets would have had about the same number of comets strike their surfaces. Studies of how stars evolve suggest that the early Sun was only about 70 percent as luminous as it is now, so the temperature in Venus’ early atmosphere must have been quite a bit lower. Thus water vapor would have been able to liquefy and form oceans on Venus. But if water vapor and carbon dioxide were once so common in the atmospheres of both Earth and Venus, what became of Earth’s carbon dioxide? And what happened to the water on Venus? The answer to the first question is that carbon dioxide is still found in abundance on Earth, but now, instead of being in the form of atmospheric carbon dioxide, it is either dissolved in the oceans or chemically bound into carbonate rocks, such as the limestone and marble that formed in the oceans. If Earth became as hot as Venus, much of its carbon dioxide would be boiled out of the oceans and baked out of the crust. Our planet would soon develop a thick, oppressive carbon dioxide atmosphere much like that of Venus. To answer the question about Venus’ lack of water, we must return to the early history of the planet. Just as on present-day Earth, the oceans of Venus limited the amount of atmospheric carbon dioxide by dissolving it in the oceans and binding it up in carbonate rocks. But being closer to the Sun than Earth is, enough of the liquid water on Venus would have vaporized to create a thick cover of water vapor clouds. Since water vapor is a greenhouse gas, this humid atmosphere—perhaps denser than Earth’s present-day atmosphere, but far less dense than the atmosphere that envelops Venus today—would have efficiently trapped heat from the Sun. At first, this would have had little effect on the oceans of Venus. Although the temperature would have climbed above 100° C, the boiling point of water at sea level on Earth, the added atmospheric pressure from water vapor would have kept the water in Venus’ oceans in the liquid state. This hot and humid state of affairs may have persisted for several hundred million years. But as the Sun’s energy output slowly increased over time, the temperature at the surface would eventually have risen above 374°C.  Above this temperature, no matter what the atmospheric pressure, Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect.  This would have made the temperature even higher and caused the oceans to evaporate faster, producing more water vapor.  That, in turn, would have further intensified the greenhouse effect and made the temperature climb higher still.  Once Venus’ oceans disappeared, so did the mechanism for removing carbon dioxide from the atmosphere. With no oceans to dissolve it, outgassed carbon dioxide began to accumulate in the atmosphere, intensifying the greenhouse effect even more. Temperatures eventually became high enough to “bake out” any carbon dioxide that was trapped in carbonate rocks. This liberated carbon dioxide formed the thick atmosphere of present-day Venus. Over time, the rising temperatures would have leveled off, solar ultraviolet radiation having broken down atmospheric water vapor molecules into hydrogen and oxygen. With all the water vapor gone, the greenhouse effect would no longer have accelerated.