Narrator: Listen to part of a lecture in an astronomy class.

旁白：听一段天文学的演讲。

Professor: There’s been a lot of talk recently about life on Mars, at the level of microorganisms anyway, mainly because of a few important discoveries and inventions.

教授：最近关于火星上的生命的谈话特别多，总之是在微生物的层面上讨论，这些主要是由于最近一些重要的发现和发明。

For example, one major discovery was that at one point water was present on Mars.

比如，一个主要的发现是：曾几何时，在火星上是有水的。

How do we know?

我们是怎么知道的？

Well, in 2004, an exploration robot discovered jarosite there.

在2004年，一个探索机器人在那里发现了黄钾铁矾。

Jarosite is a yellowish brown mineral with a crystalline structure that’s also found on Earth.

黄钾铁矾是一种有着晶状结构的黄棕色的矿物质，这个在地球上也存在。

It contains iron, potassium and hydroxide.

它还有铁、钾和氢氧化物。

The interesting thing is that on Earth at least it needs highly acidic water to form.

有趣的是，在地球上它的形成是需要强酸性的水。

So we’ve got water or had it at one point.

所以，我们有水，或者说一度有水。

And since most planetary scientists believe that water is essential to life, the presence of jarosite means that one prerequisite for life was once present on Mars.

由于大部分的地球学家认为，水对于生命是很重要的，黄钾铁矾的存在意味着，在火星上生命存在的先决条件曾经存在过。

But there’s another thing about jarosite.

但是关于黄钾铁矾有另一件事。

One step in its formation on Earth involves microorganisms; they actually speed up the formation of jarosite dramatically.

在地球上，它形成的其中一步牵涉到微生物；事实上，他们大大地加快了黄钾铁矾的形成。

Now, theoretically it is possible for jarosite to form without the help of biological life forms.

现在，从理论上来说，黄钾铁矾是可能在没有生物体的帮助下形成的。

But we don’t really know for sure if this happens ‘cause… well, because every corner of Earth has some form of biological life.

但是，我们不是很肯定这个是不是真的会发生，因为在地球上任意角落都会有一些形态生物体的存在。

But jarosite on Earth incorporates all kinds of microorganisms into its crystalline structure.

但是，在地球上的黄钾铁矾在它的晶状结构中包含了所有种类的微生物。

So it’s possible that if the jarosite on Mars was also formed with the help of microorganisms, we might be able to detect remnants of them in the samples we find.

那么，在火星上的黄钾铁矾是在微生物的帮助下形成的是有可能的，我们也可能在我们做找到的样品中发现他们的残留物。

And we have instruments now that will enable us to try to do this.

我们现在拥有可以这样操作的仪器。

For example, there’s a new instrument called the microfabricated organic analyzer, or M.O.A.

比如，现在有一个新的工具叫做“微结构有机分析器”，或“M.O.A”。

The organic analyzer is an amazing tool.

这个有机分析器是个很神奇的工具。

It will be able to collect soil samples and analyze them right there on Mars, pure, untouched samples.

它可以在火星上收集土壤样本，并在那里分析这些样本，这些纯粹的、没有碰触过的样本。

It will let us eliminate the risk we would take of contaminating the samples if they were brought back to Earth.

这个避免了样本被带回地球收到污染的风险。

And what they’ll look for specifically in the soil is amino acids.

他们在这些土壤中尤其想要找到的是氨基酸。

Amino acids, as you may know, are the building blocks of proteins.

就像你们可能知道的，氨基酸是蛋白质的构造模块。

In fact, there are twenty standard amino acids involved in making proteins and lots more that aren’t.

事实上，为了形成蛋白质，有20种常规的氨基酸会被牵涉到，但是有更多的氨基酸并没有涉及到。

And here’s the important thing.

这里有意见很重要的事情。

Amino acids are what we call handed.

氨基酸是我们所谓的有手的。

They can exist in two forms, which are mirror images of each other like hands.

他们以2种形式存在，就像手那样互相是对方的镜像。

Right and left hands have the same number of fingers in the same order plus one thumb.

左手和右手有着相同数量的手指，并且顺序相同，外加一个拇指。

But right and left hands are not the same; they are mirror images.

但是，左手和右手并不完全相同，他们是镜面的。

Well, like hands, amino acids can be right or left-handed.

就像手一样，氨基酸也可以是左手和右手。

And the twenty that make up the proteins on Earth are all left-handed.

所有构成蛋白质的那20种氨基酸都是左手的。

Now, one reason the M.O.A., the organic analyzer is so impressive is that it tests not just for the presence of amino acids but also for the handedness of amino acids.

M.O.A这种有机分析器令人惊艳的一个原因就是：它不仅测试了氨基酸是否存在，而且还测试出了氨基酸的左右手。

If amino acids are found, it would be especially interesting if they show a prevalence of one type of handedness, either left, like amino acids on Earth, or right.

如果氨基酸被发现，如果它们显示一种类型手性的普遍性，像地球上氨基酸的左旋，亦或是右旋，那都将会是非常有意思的事情。

See, other physical processes in space, processes that don’t involve living organisms, can create amino acids.

在宇宙中其他一些物理过程，那些不牵涉到生物体的过程，是可以创造出氨基酸的。

But the ones synthesized through abiotic processes, which is to say not involving microorganisms, occur in equal numbers of right- and left-handed.

但是，那些通过非生物的过程合成的氨基酸，也就是说不牵涉到微生物的那一些，左右手出现的数量是一样的。

So, a prevalence of left-handed amino acids would indicate they were biological in origin, which would be amazing!

所以，如果左手氨基酸比较普遍的话就预示着它们是起源于生物的，这个就太令人激动了！

A prevalence of right-handed ones…well, that would be really amazing!!

如果右手比较普遍，那么，那也很另人激动，

Because the organisms that created them would be unlike anything we have on Earth, which produce only left-handed ones.

因为创造出它们的生物体可能和我们地球上创造左手氨基酸的都不一样。