3 moons and a planet that could have alien life | James Green

翻译人员: Kai Lu 校对人员: Yolanda Zhang

Is there life beyond Earth in our solar system?

在地球以外，太阳系里还有生命吗？

Wow, what a powerful question.

哇，多么掷地有声的问题！

You know, as a scientist --

作为一名科学家——

planetary scientist --

行星科学家——

we really didn't take that very seriously until recently.

我们很久以来都没有认真的 考虑过这个问题。

Carl Sagan always said,

卡尔·萨根 （译注：美国天文学家）常说，

"It takes extraordinary evidence for extraordinary claims."

”非凡的断言需要有非凡的证据”。

And the claims of having life beyond Earth

地球之外有生命的断言

need to be definitive,

必须是明确的，

they need to be loud

必须是响亮的,

and they need to be everywhere for us to be able to believe it.

还需要证据充分，这样我们才会相信。

So how do we make this journey?

那么，我们要如何开始这段旅行呢？

What we decided to do

我们决定

is first look for those ingredients for life.

首先去寻找生命的基本要素。

The ingredients of life are:

生命的基本要素是：

liquid water --

液态水——

we have to have a solvent,

我们需要溶剂，

can't be ice, has to be liquid.

不能是冰，必须是液态的。

We also have to have energy.

我们还需要能量。

We also have to have organic material --

有机物质也是必不可少的——

things that make us up,

这些都是组成我们的生命体，

but also things that we need to consume.

以及供我们消耗的东西。

So we have to have these elements

环境中必须长期存在

in environments for long periods of time

这些元素

for us to be able to be confident that life,

才会让我们相信：

in that moment when it starts,

生命在诞生的那一刻，

can spark and then grow and evolve.

能够迸发出火花， 并且能够成长和演变。

Well, I have to tell you that early in my career,

我必须坦白， 在我职业生涯早期，

when we looked at those three elements,

当我们研究这三个要素时，

I didn't believe that they were beyond Earth

我并不相信它们能在地球之外

in any length of time and for any real quantity.

存在足够长的时间，或达到足够的规模。

Why? We look at the inner planets.

为什么？让我们看看太阳系的行星：

Venus is way too hot -- it's got no water.

金星太热——所以没水。

Mars -- dry and arid.

火星——干旱贫瘠，

It's got no water.

也不会有水。

在太阳系中比火星更远的地方，

And beyond Mars,

the water in the solar system is all frozen.

水全部冻成了固态的冰。

But recent observations have changed all that.

但是最近的观测改变了这一切。

It's now turning our attention to the right places

现在它把我们的注意力 带到了正确的地方，

for us to take a deeper look

让我们去进一步观察，

and really start to answer our life question.

并且真正开始回答生命的问题。

So when we look out into the solar system,

那么，当我们探索太阳系时，

where are the possibilities?

生命可能存在于哪里呢？

We're concentrating our attention on four locations.

我们将注意力集中在以下四处：

The planet Mars

火星

and then three moons of the outer planets:

和更远的三个卫星：

Titan, Europa and small Enceladus.

泰坦（土卫六），欧罗巴（木卫二） 和小小的恩赛拉多斯（土卫二）。

So what about Mars?

火星到底是什么情况呢？

Let's go through the evidence.

让我们看看证据。

Well, Mars we thought was initially moon-like:

起初我们以为火星像月亮一样：

full of craters, arid and a dead world.

布满陨石坑，荒凉，没有生命。

And so about 15 years ago,

大约在15年前，

we started a series of missions to go to Mars

我们开始了一系列登陆火星的任务，

and see if water existed on Mars in its past

去查看那里过去是否有水存在过，

that changed its geology.

还因此改变了它的地质。

We ought to be able to notice that.

我们应该可以观察得到。

And indeed we started to be surprised right away.

而实际上，我们一开始就很惊讶。

Our higher resolution images show deltas and river valleys and gulleys

高清图片显示， 那里有三角洲，河谷和沟渠，

that were there in the past.

它们过去都曾存在过。

事实上，

And in fact,

Curiosity --

好奇号探测车

which has been roving on the surface now for about three years --

在火星表面上漫游已经有三年了——

has really shown us that it's sitting in an ancient river bed,

我们看到它停在一条古老的河床上，

where water flowed rapidly.

那里曾有过湍急的水流。

And not for a little while,

时间还不短，

perhaps hundreds of millions of years.

可能曾持续过数亿年之久。

And if everything was there,

如果所有要素都存在，

including organics,

包括有机物在内，

perhaps life had started.

也许生命曾在那里诞生过。

Curiosity has also drilled in that red soil

好奇号还在红土上打了洞，

and brought up other material.

并且发现了其他物质。

And we were really excited when we saw that.

我们看到后非常兴奋，

Because it wasn't red Mars,

因为那不是红色的物质，

it was gray material,

而是灰色的，

it's gray Mars.

火星地表下面是灰色的。

We brought it into the rover,

我们把挖出来的东西带回探测车，

we tasted it,

仔细地分析了它，

and guess what?

你们猜怎么着？

We tasted organics --

我们分析出了有机物——

carbon, hydrogen, oxygen,

碳，氢，氧，

nitrogen, phosphorus, sulfur --

氮，磷，硫——

they were all there.

统统都有。

So Mars in its past,

所以过去的火星

with a lot of water,

曾有很多的水，

perhaps plenty of time,

也许存在过很长时间，

could have had life,

可能有过生命，

could have had that spark,

可能有过生命的火花，

could have grown.

还可能繁衍过一段时间。

And is that life still there?

那时候的生命还在么？

We don't know that.

我们不知道。

But a few years ago

但是几年前，

we started to look at a number of craters.

我们开始观察一些陨石坑。

During the summer,

在夏季，

dark lines would appear down the sides of these craters.

陨石坑的边沿会出现深色的线条。

The more we looked,

随着我们观察得越多，

看到的陨石坑越多，

the more craters we saw,

the more of these features.

这样的特征也越多。

We now know more than a dozen of them.

现在已知的已经超过十二个了。

A few months ago the fairy tale came true.

几个月前，童话故事成真了！

We announced to the world that we know what these streaks are.

我们向世界宣布， 我们已经知道这些条纹是什么了。

It's liquid water.

是液态水。

These craters are weeping during the summer.

这些陨石坑在夏天浸出水分。

Liquid water is flowing down these craters.

这些液态水顺着陨石坑向下流。

So what are we going to do now --

我们接下来要做什么——

now that we see the water?

在发现了液态水之后？

Well, it tells us that Mars has all the ingredients necessary for life.

这说明火星拥有生命的所有必需成分。

In its past it had perhaps two-thirds of its northern hemisphere --

在过去，可能它的北半球有三分之二

there was an ocean.

都曾是海洋。

It has weeping water right now.

现在它有冒出的水流。

Liquid water on its surface.

星球表面有液态水。

It has organics.

它有有机物。

It has all the right conditions.

它有一切合适（孕育生命）的条件。

So what are we going to do next?

那么我们接下来要做什么呢？

我们将开展一系列任务

We're going to launch a series of missions

to begin that search for life on Mars.

开始寻找火星上的生命。

And now it's more appealing than ever before.

现在行动要比以往 任何时候都更有吸引力。

As we move out into the solar system,

在离地球更远的太阳系里，

here's the tiny moon Enceladus.

有一个小小的土卫二。

This is not in what we call the traditional habitable zone,

它不在我们以往公认的宜居区域内，

this area around the sun.

也就是靠近太阳的区域。

This is much further out.

这里离太阳很远。

This object should be ice over a silicate core.

这个星球应该像个 被冰层覆盖的硅酸盐核心。

But what did we find?

但我们找到了什么？

Cassini was there since 2006,

自2006年起，卡西尼太空船就在那里，

and after a couple years looked back after it flew by Enceladus

在飞过土卫二的几年后，再回过头看，

and surprised us all.

我们都大吃一惊。

Enceladus is blasting sheets of water out into the solar system

土卫二在向太阳系喷出一片片的水，

and sloshing back down onto the moon.

再回落到它的表面。

What a fabulous environment.

多么美妙的环境啊。

Cassini just a few months ago also flew through the plume,

卡西尼太空船几个月前 又从这些飞溅的水流中穿过，

and it measured silicate particles.

它检测到了硅酸盐颗粒。

Where does the silica come from?

这些硅从哪来的？

It must come from the ocean floor.

它肯定是从海底来的。

The tidal energy is generated by Saturn,

土星产生的潮汐动能

pulling and squeezing this moon --

拉扯，挤压着这个星球——

is melting that ice,

正融化那里的冰，

creating an ocean.

形成着海洋。

But it's also doing that to the core.

这潮汐能同样 拉扯挤压着硅酸盐核心。

Now, the only thing that we can think of

我们唯一能想到

that does that here on Earth as an analogy ...

地球上类似的现象是——

are hydrothermal vents.

深海热泉。

Hydrothermal vents deep in our ocean were discovered in 1977.

深海热泉在1977年的时候 在海洋深处被发现。

Oceanographers were completely surprised.

海洋学家们对此非常惊讶。

And now there are thousands of these below the ocean.

如今在海洋之下 有成千上万这样的深海热泉。

What do we find?

我们找到了什么？

The oceanographers, when they go and look at these hydrothermal vents,

当海洋学家们研究这些深海热泉时发现

they're teeming with life,

那里有富饶的生命，

regardless of whether the water is acidic or alkaline --

不管水是酸性的还是碱性的——

doesn't matter.

这不重要。

So hydrothermal vents are a fabulous abode for life here on Earth.

地球上的深海热泉是生命的绝佳住所。

So what about Enceladus?

那么土卫二呢？

Well, we believe because it has water

我们相信因为它有水，

and has had it for a significant period of time,

并且在相当长的一段时间里拥有水，

and we believe it has hydrothermal vents

加上我们认为它有深海热泉，

with perhaps the right organic material,

以及适合的有机物质。

it is a place where life could exist.

那是一个生命可能存在的地方。

And not just microbial --

并且不仅仅是微生物——

maybe more complex because it's had time to evolve.

可能存在更复杂的生命， 因为它有足够的时间去进化。

Another moon, very similar,

另一个非常相似的卫星，

is Europa.

木卫二。

Galileo visited Jupiter's system in 1996

伽利略号在1996年时探访了木星系统，

and made fabulous observations of Europa.

对木卫二进行了详细的观察。

Europa, we also know, has an under-the-ice crust ocean.

我们知道木卫二拥有 存在于冰层下的海洋。

Galileo mission told us that, but we never saw any plumes.

伽利略号告诉了我们这些， 但我们从未看到过任何的片状水。

But we didn't look for them.

因为我们从未找寻过它们。

Hubble,

哈勃望远镜

just a couple years ago,

就在几年前

observing Europa,

观察木卫二时，

saw plumes of water

看到了片状水，

spraying from the cracks in the southern hemisphere,

它们从南半球的裂缝中喷洒出来，

just exactly like Enceladus.

就跟土卫二一模一样。

These moons,

这些卫星

which are not in what we call a traditional habitable zone,

不在我们称作传统宜居地的区域，

that are out in the solar system,

而在太阳系更远的地方，

have liquid water.

却拥有着液态水。

And if there are organics there,

如果那里有有机物的话，

there may be life.

那里就可能有生命。

This is a fabulous set of discoveries

这是一系列绝佳的发现，

because these moons have been in this environment like that

因为这些卫星已经在这样的环境中

存在了数十亿年。

for billions of years.

Life started here on Earth, we believe, after about the first 500 million,

我们相信地球上的生命 开始于地球形成5亿年之后，

and look where we are.

看看现在的我们（进化的程度）。

These moons are fabulous moons.

这些卫星让人难以置信。

Another moon that we're looking at is Titan.

我们在研究的另一个卫星是土卫六。

Titan is a huge moon of Saturn.

土卫六是土星的一个非常大的卫星。

It perhaps is much larger than the planet Mercury.

它可能比水星还要大很多。

It has an extensive atmosphere.

它有着广阔的大气层。

非常的广阔——

It's so extensive --

and it's mostly nitrogen with a little methane and ethane --

主要成分是氮气， 还有一点点甲烷和乙烷——

that you have to peer through it with radar.

所以你需要用雷达来观测它。

And on the surface, Cassini has found liquid.

在它的表面， 卡西尼号发现了液态水。

We see lakes ...

我们看到了湖泊——

actually almost the size of our Black Sea in some places.

实际上，某些地方的湖几乎 跟我们的黑海一样大。

And this area is not liquid water;

然而这块地方并不是液态水；

it's methane.

它实际上是甲烷（译注：沼气）。

If there's any place in the solar system where life is not like us,

如果在太阳系里存在这样一个地方， 那里的生命与我们不同，

where the substitute of water is another solvent --

那里水的代替物是另一种溶剂——

and it could be methane --

可以是甲烷——

it could be Titan.

那个地方就可以是土卫六。

Well, is there life beyond Earth in the solar system?

回到这个问题： 在地球以外，在太阳系中有生命么？

We don't know yet,

我们还不知道，

but we're hot on the pursuit.

但我们正在努力寻求答案。

The data that we're receiving is really exciting

我们现在接收到的信息非常让人激动，

and telling us --

它告诉我们——

forcing us to think about this in new and exciting ways.

并迫使我们以新的 令人激动的方式去思考这个问题。

I believe we're on the right track.

我相信我们正朝着正确的方向努力。

That in the next 10 years, we will answer that question.

在接下来的10年内， 我们将能够回答这个问题。

And if we answer it,

如果我们做出了解答，

and it's positive,

并且结果是积极的，

那么太阳系中的生命将会无所不在。

then life is everywhere in the solar system.

Just think about that.

想想看吧。

We may not be alone.

我们也许并不孤单。

Thank you.

谢谢。

(Applause)

（掌声）