英语听力：自然百科 行星旅行指南：火星 Mars—5

 In the four decades since our robots first arrived, the once fuzzy ball at the end of our telescopes has steadily¹ focused into a red planet we can understand, and it is not a welcoming place. The problem is the atmosphere is so thin and cold that water exists only as solid ice in the ground or vapor² in the air, not as liquid on the surface. You might see some fine wispy³ clouds, high in the sky, but don’t bother bringing an umbrella. 

 

The whole planet is dryer⁴ than the dustiest desert on earth, and there hasn’t been a drop of rain here for millions, perhaps billions of years. The thing that fascinated me was that we could see valleys, sneaking⁵ across the surface that had clearly been carved by flowing water, so this is telling us that in the past it was different, not only that it was different in a way that made more suitable for life than it is today, and that I found truly compelling. 

 

We are very convinced that one time it was very hospitable⁶ planet, with liquid water and enough atmosphere to sustain the climate, and so now we are trying to understand how did it change, why did it change and what still might be on Mars. 

 

These are deep Martian mysteries. If Mars and earth started as sister planets, did life once festoon the Martian surface? Might it still be there? And where did all the atmosphere and water go? 

 

Solving these puzzles has challenged our planetary explorers from the moment the first Martian postcards were sent back to earth. It’s the fact that it is so much like earth that kind of makes Mars such a special place.

1 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

2 vapor   

n.蒸汽，雾气

参考例句：

• The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
• This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。

3 wispy   

adj.模糊的；纤细的

参考例句：

• Grey wispy hair straggled down to her shoulders.稀疏的灰白头发披散在她肩头。
• The half moon is hidden behind some wispy clouds.半轮月亮躲在淡淡的云彩之后。

4 dryer   

n.干衣机，干燥剂

参考例句：

• He bought a dryer yesterday.他昨天买了一台干燥机。
• There is a washer and a dryer in the basement.地下室里有洗衣机和烘干机。

5 sneaking   

a.秘密的，不公开的

参考例句：

• She had always had a sneaking affection for him. 以前她一直暗暗倾心于他。
• She ducked the interviewers by sneaking out the back door. 她从后门偷偷溜走，躲开采访者。

6 hospitable   

adj.好客的；宽容的；有利的，适宜的

参考例句：

• The man is very hospitable.He keeps open house for his friends and fellow-workers.那人十分好客，无论是他的朋友还是同事，他都盛情接待。
• The locals are hospitable and welcoming.当地人热情好客。