英语听力：自然百科 行星旅行：土星 Saturn—16

 The by-product¹ of billions of years of production from the chemical smog factory in the upper atmosphere, the grains in Titan's dunes² may literally³ fall from the sky. Like a rain of flash-frozen coffee grounds, they are swept by the wind into deep piles that cover 20 percent of the surface. And like a good coffee, these Titanian dunes are dark and rich. 

The dunes represent a massive inventory⁴ of organic materials, hundreds of times larger than all the coal, for example on the earth.  

 

You're not likely to be hauling this alien coal home, but the liquid hydrocarbons⁵ lapping on Titanian shorelines could be very useful for the return trip. 

 

There's more, let's call it fossil fuel, type energy. Then we actually have known reserves on the earth by factor, perhaps of ten or even a hundred.

 

That's a lot of gas in anyone's language. But something even more valuable might be found among the storehouse of organic molecules⁶, the answer to life, the universe, and everything.

 

How do you go from such simple materials like carbon and hydrogen and oxygen and nitrogen? To something which asks questions about where it came from, that's a huge leap. And on Titan, there's a real good possibility that some of those really difficult to understand, intermediate stages actually occurred. It hasn't gone a completion as we don't think it has, although there are some people who think that if we go to one of Titan's lakes, we will discover Titanian bacteria that have figured out how to metabolize liquid methane⁷.

 

Well, that's not a liquid that we and life forms on earth like. But maybe a life form on Titan that grew up with liquid methane would be perfectly⁸ comfortable there, and we look and shock at the thought that organisms will live in water.

 

'Oh my god. Those things on earth living in water, pity those poor earthlings. We live in liquid methane much more pleasant.'

 

Titan is the ultimate test for life in our solar system. If life exists under these alien conditions, then you might find it anywhere.

1 by-product   

n.副产品，附带产生的结果

参考例句：

• Freedom is the by-product of economic surplus.自由是经济盈余的副产品。
• The raw material for the tyre is a by-product of petrol refining.制造轮胎的原材料是提炼汽油时产生的一种副产品。

2 dunes   

沙丘( dune的名词复数 )

参考例句：

• The boy galloped over the dunes barefoot. 那男孩光着脚在沙丘间飞跑。
• Dragging the fully laden boat across the sand dunes was no mean feat. 将满载货物的船拖过沙丘是一件了不起的事。

3 literally   

adv.照字面意义，逐字地；确实

参考例句：

• He translated the passage literally.他逐字逐句地翻译这段文字。
• Sometimes she would not sit down till she was literally faint.有时候，她不走到真正要昏厥了，决不肯坐下来。

4 inventory   

n.详细目录，存货清单

参考例句：

• Some stores inventory their stock once a week.有些商店每周清点存货一次。
• We will need to call on our supplier to get more inventory.我们必须请供应商送来更多存货。

5 hydrocarbons   

n.碳氢化合物，烃( hydrocarbon的名词复数 )

参考例句：

• Hydrocarbons (HC), like carbon monoxide, represent unburned and wasted fuel. 碳氢化合物(HC)像一氧化碳一样，为未燃尽的和被浪费掉的燃料。 来自英汉非文学 - 环境法 - 环境法
• With this restricted frequency range it is not applicable to hydrocarbons. 这个较紧缩的频率范围不适用于烃类。 来自辞典例句

6 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

7 methane   

n.甲烷，沼气

参考例句：

• The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
• Methane may have extraterrestrial significance.甲烷具有星际意义。

8 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。