英语听力：自然百科 探索世界奥秘之Life On Mars(火星生命)Unit04

These discoveries raised the stakes. Here was a planet similar to our own. Mars might not have cities or civilizations. But it could be home to other smaller life forms like microbes.

Chris McKay is NASA's leading microbe expert. He believes that finding even these minute organisms would be of the utmost importance.

If we find life on Mars, what we're almost certainly gonna find are microbes, little tiny microscopic¹ organisms. You think, well, what's the big deal? Well in fact for most of Earth's history, all the life was on Earth was microbes. And so going to Mars and even finding the smallest, dumbest, littlest bug² will still be important because it'll tell us that here in our own back yard life started twice. And so the hard part is possible. The evolution into intelligence and, and humanlike beings is pretty straightforward³ compared to the question of could it get started.

And there is something about microbes that makes them well suited to surviving on Mars. They're incredibly tough.

They are the organisms also that live in the extremes. They can live in the very high temperature and very high acid and very high salt. They define the limits of life and the potential of life.

But hunting for microbes would not be easy. Mars is 6,700 kilometers wide and it has the same landmass as Earth. Microbes, on the other hand, are tiny. You could fit nearly 10 million on just your fingertip. It would be far harder than finding a needle in a haystack. Scientists had to narrow down their search. So they looked for the one thing that had to be present for life to form: a place where you could find microbes.

The search for life is the search for liquid water. Life on Earth is basically full of water. Life forms are basically little bags of water with little a, a few other ingredients added. But water is the main component⁴. Water is what makes it work.

On Earth, all life is based on water. It's the main constituent⁵ of every cell. Because water is basically inert⁶, it's the perfect medium for different types of molecule⁷ to flow around, meet and react together. It enables life to form.

microbe: a minute life form; a microorganism, especially a bacterium that causes disease

landmass: a large unbroken area of land

needle in a haystack: an item that is very hard or impossible to locate

1 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

2 bug   

n.虫子；故障；窃听器；vt.纠缠；装窃听器

参考例句：

• There is a bug in the system.系统出了故障。
• The bird caught a bug on the fly.那鸟在飞行中捉住了一只昆虫。

3 straightforward   

adj.正直的，坦率的；易懂的，简单的

参考例句：

• A straightforward talk is better than a flowery speech.巧言不如直说。
• I must insist on your giving me a straightforward answer.我一定要你给我一个直截了当的回答。

4 component   

n.组成部分，成分，元件；adj.组成的，合成的

参考例句：

• Each component is carefully checked before assembly.每个零件在装配前都经过仔细检查。
• Blade and handle are the component parts of a knife.刀身和刀柄是一把刀的组成部分。

5 constituent   

n.选民；成分，组分；adj.组成的，构成的

参考例句：

• Sugar is the main constituent of candy.食糖是糖果的主要成分。
• Fibre is a natural constituent of a healthy diet.纤维是健康饮食的天然组成部分。

6 inert   

adj.无活动能力的，惰性的；迟钝的

参考例句：

• Inert gas studies are providing valuable information about other planets,too.对惰性气体的研究，也提供了有关其它行星的有价值的资料。
• Elemental nitrogen is a very unreactive and inert material.元素氮是一个十分不活跃的惰性物质。

7 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。