英语听力：自然百科 探索世界奥秘之Alien Neighbors (寻访外星人) Unit09

He wears gloves and cleans his tools with alcohol to avoid contaminating the ancient salt samples with modern microorganisms.

"The salt round about us was crystallized out 260 million years ago, and 260 million years ago, organisms in this salt lake contributed towards the crystallization. And they became incorporated in the salt. We've taken samples of the salt back to a laboratory, and we carefully dissolve away the mineral part of the material and we feed the sample with nutrients¹ that we know encourage the growth of these special bacteria. And indeed from some of the samples, we were able to hatch out viable² bacteria that might be 260 million years old.

If ancient bacteria can be revived on earth, this may also be possible on Mars.

"Mars, many millions of years ago, had water, lakes, rivers and presumably salt lakes. And perhaps, on Mars, the salt lakes harbored populations of creatures like the ones on earth. So if one is going to look for life on Mars and our earthly experience down here is anything to go by, where better to look for life than salt deposits on Mars.

The more examples of life surviving in a dormant³ state in harsh earthly environments, the better chance of finding it on Mars. Life has a way of hanging on, from the heat of an ancient salt deposit to the freezing cold of Antarctica. A lone⁴ scientist stalks the vast plains of the southern continent. Professor E. Imre Friedmann is looking for rocks, rocks that hold some of the hardiest⁵ microbes on earth. It's not as cold as Mars here, but almost. In his giant freezer at the Florida State University in Tallahassee, Professor Friedmann keeps over 300 samples of bacteria found in rocks around the world. The bacteria are removed from rock in his laboratory.

"and we collected this rock in the Antarctic desert and this is a rock which is colonized⁶ by microorganisms. The surface is lifeless, but under the surface, here, microorganisms exist which can be seen in this black zone and the leached⁷ white zone. The surface of that rock is also to isolate⁸ the microorganisms in this laboratory and grow them. We'll transfer pieces into the sterile⁹ medium.

One day, we may isolate sleeping Martians in a similar way.

"I m putting this enrichment culture here in the light because these microorganisms like plants need sunlight. This is a rock which has been placed here about two months ago.

Here are the bacteria that have thrived in some of the toughest cold conditions that...

words in this passage

crystallize: If a liquid crystallizes, it turns into crystals.结晶

stalk:昂首阔步；大步走

leach:to remove a substance from a material, especially from earth, by the process of water moving through the material, or to remove parts of a material using water:滤去

sterile:completely clean and free from dirt and bacteria:无细菌的；消毒的

1 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

2 viable   

adj.可行的，切实可行的，能活下去的

参考例句：

• The scheme is economically viable.这个计划从经济效益来看是可行的。
• The economy of the country is not viable.这个国家经济是难以维持的。

3 dormant   

adj.暂停活动的；休眠的；潜伏的

参考例句：

• Many animals are in a dormant state during winter.在冬天许多动物都处于睡眠状态。
• This dormant volcano suddenly fired up.这座休眠火山突然爆发了。

4 lone   

adj.孤寂的，单独的；唯一的

参考例句：

• A lone sea gull flew across the sky.一只孤独的海鸥在空中飞过。
• She could see a lone figure on the deserted beach.她在空旷的海滩上能看到一个孤独的身影。

5 hardiest   

能吃苦耐劳的，坚强的( hardy的最高级 )； （植物等）耐寒的

参考例句：

• This trip will season even the hardiest traveller. 这个旅行会让最坚硬的旅行者适应。

6 colonized   

开拓殖民地，移民于殖民地( colonize的过去式和过去分词 )

参考例句：

• The area was colonized by the Vikings. 这一地区曾沦为维京人的殖民地。
• The British and French colonized the Americas. 英国人和法国人共同在美洲建立殖民地。

7 leached   

v.（将化学品、矿物质等）过滤( leach的过去式和过去分词 )；（液体）过滤，滤去

参考例句：

• They believe that the humic materials are leached from decaying plant materials. 他们认为腐植物料是从腐烂的植物体浸沥而来。 来自辞典例句
• The concept holds that uranium is leached by groundwater from tuffeceous rocks. 该理论认为，来自凝灰岩的地下水淋蚀铀。 来自辞典例句

8 isolate   

vt.使孤立，隔离

参考例句：

• Do not isolate yourself from others.不要把自己孤立起来。
• We should never isolate ourselves from the masses.我们永远不能脱离群众。

9 sterile   

adj.不毛的，不孕的，无菌的，枯燥的，贫瘠的

参考例句：

• This top fits over the bottle and keeps the teat sterile.这个盖子严实地盖在奶瓶上，保持奶嘴无菌。
• The farmers turned the sterile land into high fields.农民们把不毛之地变成了高产田。