『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 54 Passage 3阅读练习，TPO/Official 54 Passage 3原文答案解析，TPO/Official 54 Passage 3阅读原文练习音频翻译。

托福TPO/Official 54 Passage 3阅读原文题目答案及解析-新东方托福官方网校手机版

生命的出现需要一系列化学元素来构成细胞的组成部分。

The creation of life requires a set of chemical elements for making the components of cells.

地球上的生命使用了92种的天然化学元素中的25种元素，尽管只有四种元素（氧、碳、氢和氮）组成了96%的生物。

Life on Earth uses about 25 of the 92 naturally occurring chemical elements, although just 4 of these elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96 percent of the mass of living organisms.

因此，生命的第一要素可能是生物所需的大多数或者所有元素的存在。

Thus, a first requirement for life might be the presence of most or all of the elements used by life.

有趣的是，这个要求基本所有地方都能满足。

Interestingly, this requirement can probably be met by almost any world.

科学家们决定，宇宙中除了氢和氦（还有一种微量元素锂）以外，所有的化学元素都是恒星产生的。

Scientists have determined that all chemical elements in the universe besides hydrogen and helium (and a trace amount of lithium) were produced by stars.

这些都是重元素，因为他们的质量比氢和氦更大。

These are known as heavy elements because they are heavier than hydrogen and helium.

与氢和氦相比，尽管所有这些重元素都很稀少，但在所有地方都能找到。

Although all of these heavy elements are quite rare compared to hydrogen and helium, they are found just about everywhere.

恒星持续产生重元素，并且伴随着恒星死亡释放出来，所以较氢和氦而言，它们的数量随着时间流逝在逐渐增加。

Heavy elements are continually being manufactured by stars and released into space by stellardeaths, so their amount compared to hydrogen and helium gradually rises with time.

重元素占据太阳系中化学物质（质量）的2%，另外的98%是氢和氦。

Heavy elements make up about 2 percent of the chemical content (by mass) of our solar system; the other 98 percent is hydrogen and helium.

在重元素产生之前形成的古老恒星系中，重元素质量少于0.1%。

In some very old star systems, which formed before many heavy elements were produced, the heavy-element share may be less than 0.1 percent.

然而，已经研究过的每个星系中至少都有一些生命所需的所有元素。

Nevertheless, every star system studied has at least some amount of all the elements used by life.

此外，当微行星（在早期太阳系中形成的微小的固态物体可能累积成行星）在一个恒星形成系统中凝结时，它们不可避免地由重元素制成，因为更普通的氢和氦仍然是气体。

Moreover, when planetesimals—small, solid objects formed in the early solar system that may accumulate to become planets—condense within a forming star system, they are inevitably made from heavy elements because the more common hydrogen and helium remain gaseous.

因此，星子会含有生命所需的元素，也意味着由小行星衍生的物体（行星、月球、小行星、彗星）也包含这些元素。

Thus, planetesimals everywhere should contain the elements needed for life, which means that objects built from planetesimals—planets, moons, asteroids, and comets—also contain these elements.

太阳系形成的原因解释了为什么地球包含生命所需的所有元素，这也是为什么我们期待这些元素在整个太阳系、星系甚至是宇宙中的其它地方被发现。

The nature of solar-system formation explains why Earth contains all the elements needed for life, and it is why we expect these elements to be present on other worlds throughout our solar system, galaxy, and universe.

这个理论不会改变，即使我们知道有些生命和地球上的生命不同。

Note that this argument does not change, even if we allow for life very different from life on Earth.

地球上的生命是以碳为基础，大多数生物学家相信其它星球的生命也可能以碳为基础。

Life on Earth is carbon based, and most biologists believe that life elsewhere is likely to be carbon based as well.

然而，我们也不能完全排除以其它化学物质为基础的生命的可能性，比如硅或氮。

However, we cannot absolutely rule out the possibility of life with another chemical basis, such as silicon or nitrogen.

以其它元素为基础的生命使用的元素（或者是相对的比例）可能与地球上以碳为基础的生命有所不同。

The set of elements (or their relative proportions) used by life based on some other element might be somewhat different from that used by carbon-based life on Earth.

但这些元素依然是恒星的产物，同样会以星子的形式存在在任何地方。

But the elements are still products of stars and would still be present in planetesimals everywhere.

不管我们在找寻什么类型的生命，我们都可能在宇宙中几乎所有的行星、月球、小行星和彗星上找到必须的元素。

No matter what kinds of life we are looking for, we are likely to find the necessary elements on almost every planet, moon, asteroid, and comet in the universe.

一个似乎更严格的要求是这些元素以分子这样现成的生命基础存在，正如早期地球上的氨基酸有机汤和其它复杂的分子。

A somewhat stricter requirement is the presence of these elements in molecules that can be used as ready-made building blocks for life, just as early Earth probably had an organic soup of amino acids and other complex molecules.

地球上的有机分子可能来自于三种来源的某些组合：大气中的化学反应，海洋中深海烟囱附近的化学反应，以及小行星和彗星携带到地球的分子。

Earth’s organic molecules likely came from some combination of three sources: chemical reactions in the atmosphere, chemical reactions near deep-sea vents in the oceans, and molecules carried to Earth by asteroids and comets.

前两种来源分别只能发生在有大气和海洋的星球。

The first two sources can occur only on worlds with atmospheres or oceans, respectively.

但第三种来源会给太阳系的所有地方带来相似的分子。

But the third source should have brought similar molecules to nearly all worlds in our solar system.

对小行星和彗星的研究表明有机分子广泛分布于小行星和彗星。

Studies of meteorites and comets suggest that organic molecules are widespread among both asteroids and comets.

在重度撞击时期（大约40亿年前），由于太阳系中的每个星体都不断被小行星和彗星撞击，每一个星体都应该接受过一些有机分子。

Because each body in the solar system was repeatedly struck by asteroids and comets during the period known as the heavy bombardment (about 4 billion years ago), each body should have received at least some organic molecules.

然而，这些分子会被不受大气保护的表层太阳辐射所破坏。

However, these molecules tend to be destroyed by solar radiation on surfaces unprotected by atmospheres.

而且，这些分子可能在表层之下保存完好（就像它们明显在小行星和彗星上保存完好），除非有某种液体或者气体移动它们，否则它们也许不能相互发生反应。

Moreover, while these molecules might stay intact beneath the surface (as they evidently do on asteroids and comets), they probably cannot react with each other unless some kind of liquid or gas is available to move them about.

因此，如果我们的研究范围限制到有机分子可能参与到化学反应中的星球，那我们就能排除掉没有大气和表层或地下的液体媒介（比如水）那样的星球。

Thus, if we limit our search to worlds on which organic molecules are likely to be involved in chemical reactions, we can probably rule out any world that lacks both an atmosphere and a surface or subsurface liquid medium, such as water.

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

According to paragraphs 1 and 2, living cells contain which of the following?

Why does the author provide the information that "Heavy elements...stellar deaths"?

Paragraph 3 suggests that which of the following may be a difference between very old star systems and newer star systems?

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

The word “inevitably” 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, which of the following is true about possible life on other planets?

According to paragraph 5, all of the following are true of the organic molecules on early Earth EXCEPT:

The phrase “widespread among” is closest in meaning to

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

According to paragraph 6, why is life unlikely to be found on any planet that lacks both an atmosphere and a surface or subsurface liquid medium?

Look at the four squares  that indicate where the following sentence could be added to the passage. To answer the question “Could life exist on other planets?” we must first look at the necessary preconditions for life.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Elements of Life The creation of life requires a set of chemical elements for making the components of cells.  Life on Earth uses about 25 of the 92 naturally occurring chemical elements, although just 4 of these elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96 percent of the mass of living organisms.  Thus, a first requirement for life might be the presence of most or all of the elements used by life.  Interestingly, this requirement can probably be met by almost any world. Scientists have determined that all chemical elements in the universe besides hydrogen and helium (and a trace amount of lithium) were produced by stars. These are known as heavy elements because they are heavier than hydrogen and helium. Although all of these heavy elements are quite rare compared to hydrogen and helium, they are found just about everywhere. Heavy elements are continually being manufactured by stars and released into space by stellardeaths, so their amount compared to hydrogen and helium gradually rises with time. Heavy elements make up about 2 percent of the chemical content (by mass) of our solar system; the other 98 percent is hydrogen and helium. In some very old star systems, which formed before many heavy elements were produced, the heavy-element share may be less than 0.1 percent. Nevertheless, every star system studied has at least some amount of all the elements used by life. Moreover, when planetesimals—small, solid objects formed in the early solar system that may accumulate to become planets—condense within a forming star system, they are inevitably made from heavy elements because the more common hydrogen and helium remain gaseous. Thus, planetesimals everywhere should contain the elements needed for life, which means that objects built from planetesimals—planets, moons, asteroids, and comets—also contain these elements. The nature of solar-system formation explains why Earth contains all the elements needed for life, and it is why we expect these elements to be present on other worlds throughout our solar system, galaxy, and universe. Note that this argument does not change, even if we allow for life very different from life on Earth. Life on Earth is carbon based, and most biologists believe that life elsewhere is likely to be carbon based as well. However, we cannot absolutely rule out the possibility of life with another chemical basis, such as silicon or nitrogen. The set of elements (or their relative proportions) used by life based on some other element might be somewhat different from that used by carbon-based life on Earth. But the elements are still products of stars and would still be present in planetesimals everywhere. No matter what kinds of life we are looking for, we are likely to find the necessary elements on almost every planet, moon, asteroid, and comet in the universe. A somewhat stricter requirement is the presence of these elements in molecules that can be used as ready-made building blocks for life, just as early Earth probably had an organic soup of amino acids and other complex molecules. Earth’s organic molecules likely came from some combination of three sources: chemical reactions in the atmosphere, chemical reactions near deep-sea vents in the oceans, and molecules carried to Earth by asteroids and comets. The first two sources can occur only on worlds with atmospheres or oceans, respectively. But the third source should have brought similar molecules to nearly all worlds in our solar system. Studies of meteorites and comets suggest that organic molecules are widespread among both asteroids and comets. Because each body in the solar system was repeatedly struck by asteroids and comets during the period known as the heavy bombardment (about 4 billion years ago), each body should have received at least some organic molecules. However, these molecules tend to be destroyed by solar radiation on surfaces unprotected by atmospheres. Moreover, while these molecules might stay intact beneath the surface (as they evidently do on asteroids and comets), they probably cannot react with each other unless some kind of liquid or gas is available to move them about. Thus, if we limit our search to worlds on which organic molecules are likely to be involved in chemical reactions, we can probably rule out any world that lacks both an atmosphere and a surface or subsurface liquid medium, such as water.