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本帖最后由 hycqy 于 2010-9-20 21:40 编辑
Professor:
Last week, we covered some argumentsagainst going back to the Moon. But there arecompelling reasons in favor of another Moon landing too(主旨句),(蓝色句子和红色句子可以看出文章的主题是想解释为什么要再次登月) um… not the least of which is trying to pinpoint the moon’s age(理由1). We could do this in theoryby studying an enormous impact crater, known as the South Pole- Aitken Basin.Um…it’s located in the moon’s South Polar Region.But, since it’s on the far side of the moon, it can only be seen from space.Here is an image of…we’ll call it the SPA
Basin.This color-coated image of the SPA Basin, those aren’t itsactual colors obviously, this image is from the mid 90s, from the Americanspacecraft called Clementine. Um… unlike earlier lunar missions, Clementine didn’t orbit only around the moon’s equator. Itsorbits enable it to send back data to create this topographical map of … well,the grey and white area towards the bottom is the South Pole, the purples andblues in the middle correspond to low elevations - the SPA Basin itself,the oranges and reds around it are higher elevations. The basin measures anamazing 2,500 km indiameter, and its average depth is 12 km.That makes it the biggest known crater in our solar system and it may well bethe oldest.
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为了支持理由1 运用了对比 SPA是传统做法
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You know planetary researchers love studying deep craters until learn about the impacts that created them, how theyredistributed pieces of a planet’s crust and in this case, we especially want to know if any of the mantle, the layer beneath the crust, was exposed by theimpact. Not everyone agrees, but some experts are convinced that whatevercreated the SPA
Basin did penetrate the Moon’s mantle.And we need to find out, because much more than the crust, the mantle contains information about a planet’s or Moon’s totalcomposition. And that’s key to understanding planet formation. Um… Dian?
Dian: So, the only way to know thebasin’s age is to study its rocks directly? Professor: well, from radio surveydata, we know that the basin contains lots of smallercraters. So it must be really old, about 4 billion years, give or take afew hundred million years. But that’s not very precise. If we had rock samplesto study, we’d know whether the small craters were formed by impacts during thefinal stages of planetary formation, or if they resulted from later meteorshowers.5 p3 |4 x0 t% A0 H
通过一问一答 表现出SPA的局限性 也就是不够精确
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Dian: But if we know around how old theBasin is, I’m not sure that’s reason enough to go to the Moon again.: W3 a! c' G$ _5 k
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Professor: No…,but such crude estimates…um…we can do better than that.
仍然是在说不够精确
Besides, thereare other things worth investigating, like is there water ice on the moon(理由2)?Clementine’s data indicated that the wall of the south-polar crater was more reflective than expected. So some experts think there’s probably ice there.Also, data from a later mission indicates significant concentrations of hydrogen and by inference water lessthan a meter underground at both poles.
Student: Well if there’s water, how didit get there? Underground rivers?
Professor: We think meteors that crashedinto the moon or tails of passing comets may have introduced water molecules.Any water molecules that found their way to the floors of craters near themoon’s poles, that water would be perpetually frozen, because the floors ofthose craters are always in shadow. Um…furthermore, if the water ice was mixedin with rock and dust, it would be protected from evaporation.
Dian: So are you saying there might beprimitive life on the moon?
Professor: that’s not my point at all. Um… o.k.,say there is water ice on the moon. That would be a very practical value for afuture moon base for astronauts. Water ice could be melted and purified fordrinking. It could also be broken down into its component parts - oxygen andhydrogen. Oxygen could be used to breathe, and hydrogencould be turned into fuel, rocket fuel. So water ice could enable thecreation of a self-sustaining moon base someday, a mining camp perhaps or adeparture point for further space exploration.
上面是在解释水是怎么来的以及如果存在水的意义 是对理由二的一个延伸
Student: But holding tons of equipmentto the moon to make fuel and build a life support system for a moon base,wouldn’t that be too expensive?/ {, Z( Z1 g9 g6 _4 Y0 W
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Professor: Permanent base, maybe a way’soff, but we shouldn’t have to wait for that. The dust at the bottom of the SPA
Basin really does have a fascinating story to tell. I wouldn’t give for a few samplesof it.
即使存在水 仍存在的困难 这还是对理由二的延伸
总体来说 教授首先给出主题 也就是再次登月的必要性 然后给出了两点必要性 一个是探究年龄 另一个是探究水的存在 剩下看似凌乱的段落都是在说明这两个主要理由 因此可以认为是总说分述的结构
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