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Narrator:Listen to part of a lecture in an Astronomy Class
独白:听下面一部分的天文学课程
Professor:Last week, we covered some arguments against going back to the Moon.
教授:上周，我们谈到了反驳回到月球的一些观点。
But there are compelling reasons in favor of another Moon landing too,
而这节课我们要谈到的是支持登月的几个充分原因。
um… not the least of which is trying to pinpoint the moon's age.
我们这样做绝不是试图得出月球的确切寿命。
We could do this in theory by studying an enormous impact crater, known as the South Pole-Aitken Basin.
理论上，我们可以通过研究一个名为南极艾特肯盆地的巨大撞击坑来得出结论。
Um…it's located in the moon's South Polar Region.
嗯，它位于月球的南极区。
But, since it's on the far side of the moon, it can only be seen from space.
但是，由于它位于距地球很远的一边，我们只能在太空中才能看到它，
Here is an image of…
我这里有一张图片。
we'll call it the SPA Basin.
我们将其命名为 SPA 盆地。
This color-coated image of the SPA Basin, those aren't its actual colors obviously,
可以看到盆地上一层着色的图层，很明显这不是真实的颜色。
this image is from the mid 90s, from the American spacecraft called Clementine.
这张图拍摄于九十年代中期，来自名为克莱门的美国宇宙飞船。
Um… unlike earlier lunar missions, Clementine didn't orbit only around the moon's equator.
不像早些时候的月球探测，嗯，克莱门飞船并没有仅仅沿着月球的轨道。
Its orbits enable it to send back data to create this topographical map of …
这种特殊的飞行使得飞船能够发送数据回地球，从而得出这张地形图。
well, the grey and white area towards the bottom is the South Pole,
延伸至底部的灰白区域是南极，
the purples and blues in the middle correspond to low elevations,
中间紫色和蓝色的部分是海拔较低的地带，
the SPA Basin itself, the oranges and reds around it are higher elevations.
而橙红色地带的SPA 盆地海拔较高。
The basin measures an amazing 2,500 km in diameter, and its average depth is 12 km.
盆地直径达到惊人的 2500 千米，平均深度达到 12 千米。
That makes it the biggest known crater in our solar system and it may well be the oldest.
这使得它成为了太阳系中已知的最大撞击坑，很可能也是年代最久远的。
You know planetary researchers love studying deep craters until learn about the impacts that created them, how they redistributed pieces of a planet's crust and in this case,
我们知道，在知道行星形成的原因之前，行星研究人员喜欢研究撞击深坑，它们如何重新分配行星的外壳物质。
we especially want to know if any of the mantle, the layer beneath the crust, was exposed by the impact.
我们特别想知道在外壳下层中是否存在某些金属因撞击而受到影响。
Not everyone agrees,
不是所有人都同意这样的说法，
but some experts are convinced that whatever created the SPA Basin did penetrate the Moon's mantle.
但是某些专家坚信不管何种物质使 SPA 盆地形成，它都会渗透过月球的金属层。
And we need to find out, because much more than the crust, the mantle contains information about a planet's or Moon's total composition.
而由于金属层包含信息比外壳要多得多，我们必须找到一个行星或是月球的整体构成要素。
And that's key to understanding planet formation. Um… Dian?
这是了解行星构成的关键所在。迪安有问题吗？
Dian:So, the only way to know the basin's age is to study its rocks directly?
迪安:那么知道盆地形成时间的唯一途径就是对其岩石进行直接的研究？
Professor:well, from radio survey data, we know that the basin contains lots of smaller craters.
教授:嗯，辐射调查的数据显示，我们知道盆地里有很多更小的火山口。
So it must be really old, about 4 billion years, give or take a few hundred million years.
因此应该有一定历史了，大概 40 亿年，允许有一亿年左右的误差。
But that's not very precise.
但也不是很精确。
If we had rock samples to study, we'd know whether the small craters were formed by impacts during the final stages of planetary formation,
如果我们研究岩石样本，我们就知道小火山口是不是在行星形成的最后阶段影响而形成的，
or if they resulted from later meteor showers.
或者是否由于最近的流星雨造成的。
Dian:But if we know around how old the Basin is, I'm not sure that's reason enough to go to the Moon again.
迪安:但如果我们知道了盆地的大概年龄，我不敢确定这是否足以成为我们再次登月的理由。
Professor:No…, but such crude estimates…um…we can do better than that.
教授:不。。这只是粗略的估计，嗯，我们能得到更为准确的数字。
Besides, there are other things worth investigating, like is there water ice on the moon?
此外，还有其他东西值得。研究，比如月球上有水冰资源吗？
Clementine's data indicated that the wall of the south-polar crater was more reflective than expected.
克莱门的数据显示南极撞击坑比人们预期的要更具有反射效果，
So some experts think there's probably ice there.
因此某些专家认为那里很可能有冰的存在。
Also, data from a later mission indicates significant concentrations of hydrogen and by inference water less than a meter underground at both poles.
同样，最近的一项月球探测任务数据显示，那里氢气高度密集，据推测，两级的水就在地下不到一米处。
Student:Well if there's water, how did it get there?
学生:嗯，如果有的话，水是怎么到达的呢？
Underground rivers?
地下河？
Professor:We think meteors that crashed into the moon or tails of passing comets may have introduced water molecules.
教授:我们认为撞击月球的流星或经过的彗星尾巴留下一些水分子。
Any water molecules that found their way to the floors of craters near the moon's poles, that water would be perpetually frozen, because the floors of those craters are always in shadow.
水分子会沿路到达月磁极旁的火山口地上，由于这些火山口的地面总是处在阴影中，水分子会永远冻结。
Um…furthermore, if the water ice was mixed in with rock and dust, it would be protected from evaporation.
嗯，还有，如果在水冰中混杂石头和灰尘，便不会容易蒸发掉。
Dian:So are you saying there might be primitive life on the moon?
迪安:那么你是不是说月球上可能有原始生物？
Professor:that's not my point at all. Um… o.k., say there is water ice on the moon.
教授:我不是这个意思。嗯，好吧，假设月球上有水冰。
That would be a very practical value for a future moon base for astronauts.
这对未来在月球上驻地的宇航员们而言将会有非常实际的价值。
Water ice could be melted and purified for drinking.
水冰可以融化过滤，供人饮用。
It could also be broken down into its component parts-oxygen and hydrogen.
同时也可以分解成氧和氢两种元素。
Oxygen could be used to breathe, and hydrogen could be turned into fuel, rocket fuel.
氧气供人呼吸，而氢气可以转化成燃料，特别是火箭燃料。
So water ice could enable the creation of a self-sustaining moon base someday, a mining camp perhaps or a departure point for further space exploration.
因此，未来自给自足的月球基地将成为可能，也许一个采矿营或者是未来太空探索的出发点。
Student:But holding tons of equipment to the moon to make fuel and build a life support system for a moon base, wouldn't that be too expensive?
学生:但是带着吨重的装备到月球去制造燃料，给月球研究基地提供生命支持系统，代价不会太高了吗？
Professor:Permanent base, maybe a way's off, but we shouldn't have to wait for that.
教授:永久基地，也许是一种解决方式，但我们不需要等那么久。
The dust at the bottom of the SPA Basin really does have a fascinating story to tell.
SPA 盆地底部的灰尘蕴藏着非常有趣的故事。
I wouldn't give for a few samples of it.
我不会错失一些样本的。
