(单词翻译:单击)
Okay, let's be honest: We have found a lot of water on Mars.
咱们来打个比方：假如人类在火星上发现了许多水源。
The planet has vast underground ice deposits, enough polar ice for a global flood,
火星有很多的地下积冰、体量足以引发全球性洪灾的极地冰，
and maybe even some sort of liquid water flowing every now and then.
甚至可能还有类似于液态水的东西时不时地出现。
By now, no one really doubts that Mars used to be wet, and that ancient water is still trapped in or on the planet.
目前为止，没有人真地质疑火星过去曾有水的情况，而且过去存在的这些水源可能依然存在于火星。
What they do argue about is whether future astronauts would be able to use that water,
他们确实谈论的到一点是：是否未来的宇航员可以用到火星上的水源，
or whether it's too inaccessible or dirty to even try.
还是说，火星上的水不是太难获得，就是太脏了不能喝。
But according to a paper in last week's issue of the journal Science,
不过，上周《科学》杂志上的一篇文章提出，
at least some places on Mars have gigantic drinkable glaciers sitting just below the surface. So get your space pickaxes ready.
火星上至少有一些表层下面确有大量冰川，其成分安全可饮用，所以，准备好凿冰的工具吧。
When we hear someone say there's ice beneath Mars's surface, it's easy to imagine buried glaciers of pure frozen water.
如果有人跟我们说，火星表面下面确有冰层存在，那很容易就能想到它们是纯净水冻结后埋地表下形成的冰川。
But that's not always what scientists mean.
不过，有时候科学家可不这样认为。
Many of them have traditionally pictured Mars's ice closer to a sort of concrete,
很多科学家以前就拍到过火星的一些照片，照片上的冰层非常近似于某种凝结物，
with ice crystals mixed with dust grains and rock fragments.
上面的冰晶与尘土颗粒、岩石碎块掺杂在一起。
Still, it's been hard to tell if that's right because so much of the ice is underneath layers of dust and rock.
不过，这一点依然难以得到证实，因为其中很大一部分冰在尘土与碎石层的下面。
We know it's there because of indirect measurements,
我们之所以知道那里有纯净的水源是因为人类有过间接的一些测量结果，
but those measurements don't tell us tons about how mixed it is with the surrounding rocks.
但这样间接的结果提供的信息不够多，所以我们也就无法得知上面的冰层是否与周围的碎石混在一起。
So in this new study, the authors looked for a more direct way of understanding Mars's ice: Pictures.
所以在这项最新研究中，作者力图寻找更直接的办法来探究火星上的冰层：图像。
They used photos from the Mars Reconnaissance Orbiter to investigate eight hills
他们用火星勘测轨道飞行器发回的照片来研究火星上的八座山，
where erosion has revealed what's beneath the surface dust, sort of like seeing the layers of rock in the Grand Canyon.
这八座山上的腐蚀情况可以表明火星表面尘土之下到底是什么，从观测到的图像里可以看到类似于大峡谷里的岩层一样的东西。
Each hill had a layer of pretty much pure ice, with hardly any rocks or dust mixed in,
每座山上都有一层含水量充足的冰层，而且冰层里也没掺入什么碎石或者尘土，
sitting within a couple meters of the surface layers.
夹杂在数米表层之间。
The scientists found the ice by looking at enhanced-color images, since everything on Mars is tinted red with dust.
科学家通过观测彩色增强图像得以发现了这些冰层，原理是火星上的一切事物都有些许红色，而且还蒙着一层灰。
And in those images, the hillside ice practically glowed blue like a glacier on Earth.
在这些图像里可以看到，山坡上的冰层反射出蓝色的光，有点像地球上的冰川。
The team also confirmed it was ice using other methods,
经该研究组通过其他一些方法证实，图像上东西的成分就是冰，
like measuring what sorts of electromagnetic radiation it gave off.
证实的方法类似于测出其所发出的电磁辐射的种类。
And they found that the ice layers were tens or even a hundred meters thick.
他们还发现，这些冰层的有几十层深宅一百层那么厚。
Those ice reserves could be vital sources of drinking water of course for future astronauts.
这些冰层储备是今后宇航员在火星上饮用水的重要来源。
But by splitting water molecules into hydrogen and oxygen, the ice could also help produce breathable air, too.
不仅如此，将冰层中的水分子分解为氢和氧之后，还能产生人类可用的空气。
But the ice sheets didn't just appear on Mars.
不过，这样的冰层并非火星的专属。
Models show that they probably came from gigantic snowstorms millions of years ago.
有模型显示，这些冰层很可能来自于几百万年之前的数场大型暴风雪。
So like on Earth, future scientists could also drill into these ice layers
所以未来的科学家也可以像研究地球一样，仔细研究这些冰层，
and learn how the Martian climate has changed over time.
看看火星气候的演变过程是怎样的。
And that could answer some surviving questions about why the Red Planet is so dry.
而且这样的研究或许能解释一些目前仍然未解的谜题，比如火星的气候为何如此干燥。
Still, before we can even think about using that water, we should probably figure out how to safely send people to Mars. Baby steps.
不过，在思考怎样利用火星水源之前，我们最应该想的是怎样将人类安全地送达火星，毕竟路要一步一步走嘛。
Besides looking at Mars, astronomers have also been working on a much larger mystery:
除了观测火星之外，宇航员也一直在试图解开一个更大的谜题，
why galaxies give off so much light. Specifically, certain wavelengths of infrared light.
那就是，银河系为何能散发这么多的光，尤其是一些红外线波长的光。
They've known about this for years, but they've had trouble identifying the culprit.
宇航员一直都是知其然，但在知其所以然方面遇到了困难。
See, no one molecule or small group of molecules seemed to exactly match the observations.
因为无论是单个分子还是一小群分子都无法与观测结果相匹配。
But another paper in the same issue of Science has helped zero in on where all that extra light is coming from.
而同期另一篇论文研究的问题又与银河系中红外线的来源无关。
With this study, the authors were trying to confirm a previously proposed idea:
通过这次的研究，文章作者试图证实一个此前提出的观点，
that the glow wasn't just from one or a few molecules, but a huge class of them.
即光源既不是来自单一分子，也不是来自几个分子，而是由一大类分子共同发出的。
This class is called polycyclic aromatic hydrocarbons, or PAHs.
这类分子的组成物就是多环芳烃(PAH)。
These are rings of carbon atoms surrounded by nothing but hydrogen.
所谓多环芳烃是由氢原子包围碳原子环组成的。
There are over a hundred different PAHs, and the larger ones tend to emit similar kinds of infrared light when they move around in empty space.
多环芳烃有一百多种，越大的多环芳烃就越容易在真空区域里移动时发出类似的红外光。
So it's possible that the glow astronomers saw from galaxies could be the combined light of dozens of distinct but similar PAHs.
所以宇航员看到的银河系发出的光源很可能是一大群只有毫厘之差的多环芳烃。
But no one has ever conclusively seen one of these molecules in outer space,
不过，由于没有人曾在外太空见过组成多环芳烃的耽搁分子，
and scientists weren't sure how they'd form.
所以科学家也无法确定这种光源的组成。
Also, their light blends together so well that it's hard to tell if any one specific molecule is actually out there.
而且，由于各种光汇聚得很好，所以很难辨别光源里是否有某种特定的分子。
That's where this new study comes in. Instead of looking for individual PAHs,
这也是这项新研究的切入点，不过，研究人员并没有试图寻找单独的多环芳烃，
the researchers used radio telescopes to search for light given off by precursor molecules that can easily react to form them.
而是用电波望远镜来寻找前体分子释放的光，因为前体分子易发生反应就能形成多环芳烃。
These molecules are sometimes known as PA(N)Hs,
这种分子也称含氮多环芳烃，也称PA(N)H，
where the "N" stands for a nitrogen atom where there would be a hydrogen in a true PAH.
其中的N就表示氮原子，这样的多环芳烃里就含有氢原子。
The additional nitrogen makes these molecules sort of off-balance,
多出来的氮原子破坏了多环芳烃的平衡性，
so they rotate and vibrate more distinctly than a lot of the symmetrical molecules do.
所以它们会像很多对称分子一样以较为特殊的方式旋转振动。
And that makes them give off more light.
从而发出更多的光。
To search for these molecules, the researchers looked at the Taurus Molecular Cloud, a cloud of gas and dust about 400 light-years away.
为了搜寻这种分子，研究人员观测了距离地球400光年的金牛座分子云。
There, they found one of these building blocks, known as benzonitrile.
通过观测，他们发现氰苯是其中的一个组成成分。
It isn't a big molecule, it only has thirteen atoms, but it is important, and finding it in outer space means we must be on the right track.
氰苯不是大分子，只由13个原子组成，但它起着重要的作用，在外太空发现了氰苯就表明我们的研究方向是对的。
Benzonitrile reacts easily with other molecules to produce exactly the kinds of PAHs that could make galaxies glow in infrared.
氰苯易与其他分子相互作用产生多环芳烃，从而使得银河系发出红外光。
So it could explain how the PAHs ended up in space in the first place.
这也就能解释多环芳烃为何最先在宇宙里消亡。
Now, there's still some way to go before this mystery is completely solved.
所以说，在这一谜团彻底解决之前，我们依然有一段路要走。
For one, we'd like to actually identify a PAH in space.
其中一个就是，我们想先在确认多环芳烃的存在性。
And there's still some uncertainty about where these precursor molecules, like benzonitrile, would come from.
然后再解决掉前体分子的来源，比如氰苯。
But now, we're at least more confident that all those steps are somewhere on the ladder.
虽然谜团重重，所幸我们至少已经确定自己步入了正轨。
We just need to fill in the details. Thanks for watching this episode of SciShow Space News!
现在只需要确认一些细节的情况，好啦，感谢收看本期的《太空科学秀》！
If you would like to get the latest updates from around the universe every week,
如果您想每周都能获取有关太空的最新资讯，
along with some other cool space science, you can go to youtube.com/scishowspace to subscribe.
和其他太空科学趣闻，请订阅我们的频道youtube.com/scishowspace。
