We live on a world of wonders.
我们生活在一个奇妙的世界里...
A place of astonishing beauty and complexity.
一个美妙而复杂的世界。
We have vast oceans
我们有广阔的海洋，
and incredible weather.
和令人难以置信的天气，
Giant mountains and spectacular landscapes.
巨大的高山和壮观的风景。
If you think that this is all there is,
如果你觉得所有的这些宏伟的景观
that our planet exists in magnificent isolation,
仅仅是存在于我们星球上，
then you're wrong.
那么你就错了。
We're part of a much wider eco-system,
我们是更广泛的生态系统的一部分，
that extends way beyond the top of our atmosphere.
它的扩展超出了我们的大气层顶端。
I think we are living through
我认为我们正经历着
the greatest age of discovery our civilisation has ever known.
一个最能够探索与发现已知文明的时代
We've voyaged to the farthest reaches of the solar system,
我们的航天器早已到达太阳系最远的地带。
photographed strange new worlds,
我们已经拍下陌生的新世界，
stood in unfamiliar landscapes,
站在这不熟悉的地方，
tasted alien air.
呼吸着陌生的空气。
Amongst all these wonders sits our Earth -
所有的这些奇迹都眷顾于我们的地球 -
an oasis of calm amidst the violence of the solar system.
暴躁太阳系中，平静的一个绿洲
And all that separates us
所有的这些外部世界，与我们隔离开的，
from what's out there is a thin, flimsy envelope of gas -
只是一层，薄薄的，脆弱的气体 -
our atmosphere.
我们的大气层。
And it's thanks to this "thin blue line"
感谢这个“薄蓝线”吧，
that we have the air that we breathe,
我们有呼吸的空气，
the water that we drink
我们有喝的清水
and the landscape that surrounds us.
和我们周围的这些风景。
Atmospheres define all the planets in the solar system.
太阳系中，大气层决定了行星的一切。
They have the power to create dynamic worlds that are alien and chaotic.
它们有能力去创造陌生而混乱的动态世界。
But, remarkably, in the frozen wastes of the solar system...
但是，值得注意的是，在太阳系的冻结废料里...
..one atmosphere has created the most unexpected wonder -
..一个由大气层创造出最意想不到的奇迹 -
a moon that looks a lot like home.
一颗看起来很像家的卫星。
本中文字幕仅供学习交流，严禁用于商业途径
太阳系的奇迹
蔚蓝色的大气层
Subtitles by Red Bee Media Ltd 字幕由红蜂媒体有限公司提供 翻译：wyman5555 校对：wyman5555
I've come to Cape Town in South Africa
我来到了南非开普敦
to do something that I have always wanted to do,
去做一些我一直都想做，
but never thought I would get the chance.
从未想过有机会做的事。
I'm about to fly incredibly high,
我要飞到很高很高，
to the very edge of the Earth's atmosphere.
非常接近地球大气层边缘的地方
From here, I am hoping to see something that only a handful of people have ever seen -
从这里，我希望能看到，只有少数人见过的 -
the thin blue line,
大气层，
the fragile strip of gas that surrounds our whole planet.
脆弱的气体，包裹住我们整个地球。
And this is what's going to take me there.
我将到达那里。
This is an English Electric Lightning,
这是英国闪电号，
the most beautiful fighter aircraft ever built.
最美丽的战斗机。
This is when England built the best aircraft in the world.
那时英国能造出世界上最好的飞机。
The Lightning is no longer in service,
闪电号不再服役了，
but this piece of magnificently overpowered engineering
但这个辉煌的制造工程
is going to take me 18 kilometres, straight up.
要带我到18公里高的上空。
Actually, I read somewhere that when you read about the altitude
其实，我听说，当你阅读关于闪电号的资料时
of the Lightning, it says "Altitude: Estimated, 60,000 feet.
它说“海拔高度：预计，6万英尺。
"Ceiling: Classified."
“最高上限：机密。”
So I don't know how high these can go.
因此，我不知道它到底能飞多高。
I have heard rumours they can go to 80,000 feet, which is amazing.
传闻说，它可以到达80,000英尺（24公里），好吓人哦。
My journey will take me beyond almost all the molecules of gas that make up our atmosphere.
旅程将带我越过构成大气层的绝大部分的气体分子。
If you feel you're going to get sick... Yeah? ..use a bag, OK? Right. Hopefully not.
如果你觉得恶心...好吗？ ..用一个袋子，OK？好，但愿不用。
To get there, I'm going to experience
为了到达那里，我要去体会
what made the Lightning famous -
是什么让闪电号如此出名 -
a vertical take-off.
垂直飞行。
Whoo-hoo!
哇，呵！
'It takes just seconds to reach nine kilometres up,
'只需短短几秒，就达到了9公里高，
'but I'm still in the thickest layer of the atmosphere,
'但我仍然在大气层最厚的地方，
'called the troposphere.
'所谓的对流层。
'But the further I climb, the thinner the atmosphere becomes.'
'进一步的攀升，大气变得越来越稀薄。'
Up at 58,000 feet. 90% of the atmosphere is below me.
达到58000英尺（17.4公里）。90％的大气在我之下。
The only people above me are on the space station.
唯一在我头顶上的人，住在国际空间站。
So beautiful.
如此美丽。
I'm now at 60,000 feet.
现在我在60,000英尺的高空。
'18 kilometres up.
'18公里高了。
'And the highest I can go.'
'这是我能去到的最高的地方了。
Above me, the sky is a deep, dark blue.
我上面的天空，深蓝色。
'And that is what I've come to see - '
'我所看到的 - '
our atmosphere.
我们的大气层。
That really is the thin blue line that protects us.
确实是蓝色的薄膜保护着我们。
So...fragile and so tenuous.
所以...脆弱得，太纤细了。
Just a tiny sliver of blue.
只是一层蓝色的小薄片。
Amazing.
令人惊讶。
55至60,000英尺，反转
Between 55 and 60,000 feet, inverted,
the curvature of the Earth there.
那里，地球曲率。
5G, vertical ascent.
5G的加速度，垂直上升。
That is just a ride!
这仅仅是一个感觉！
It is remarkable to see that.
很明显看到的。
You can see
你可以看到
the...thinness and fragility,
这...薄薄的，脆弱的，
you can see the atmosphere going from light blue, to dark blue, to black.
你可以看到大气层从浅蓝，到深蓝，再到黑色。
It really is astonishing.
真的是惊人啊。
The thin blue line makes the Earth the wonderfully diverse place it is.
蔚蓝的薄膜，使地球有了多种多样的地方。
It acts as a soothing blanket, that traps the warmth of the sun...
它像一张舒适的毯子，捕捉到温暖的阳光...
..yet protects us from the harshness of its radiation.
..也保护我们免受，严酷的辐射。
Its movements can be traced in the gentlest breeze.
它的动作既有温柔的微风。
And the most devastating hurricane.
也有最具破坏性的飓风。
The oxygen and water the atmosphere holds
大气层锁定住氧气和水
plays a fundamental role in the ongoing survival
对目前的生命起着根本性的作用
of millions of different species living on the planet.
百万计不同的物种生活在这个星球。
In this film, I want to explain how the laws of physics
本集，我将解释，物理定律如何
that created our unique atmosphere
创造了我们这独一无二的大气层
are the same laws that created many diverse and different atmospheres
同样的法则又如何创造了其他不同的大气
across the solar system.
纵横整个太阳系。
When perfectly balanced, a world as familiar
当生态完美平衡，作为熟悉的世界，
and beautiful as the Earth can evolve beneath the clouds.
美丽的地球，在大气下发展。
But the slightest changes can lead to alien and violent worlds.
但只要一丝的变化就会变成暴乱的外部世界。
There are planets in our solar system that have been transformed
这些我们太阳系的行星已变成
into hellish worlds, by nothing more than the gases in their atmosphere.
地狱般的世界，大气层气体太多了。
And just as atmospheres can choke a planet to death,
而这种稀薄到窒息的大气层，
they are also powerful enough to shape their surfaces.
还是能够塑造它们的地貌。
And there are worlds out there which are all atmosphere.
而那里，是大气构成的世界。
Giant balls of churning gas, where storms three times
巨大的漩涡气流，三倍于
the size of the Earth have raged for hundreds of years.
地球大小，已经持续了几百年。
All atmospheres in the solar system are unique,
所有的大气层，在太阳系都是独一无二的，
but the ingredients and forces that shape them are universal.
但构成的成分和力量，是一样的。
At the heart of each is the glue which holds the solar system together,
其核心，胶水般把太阳系连为一体，
a fundamental force of nature -
是大自然的基本力量 -
gravity.
引力。
Gravity is, by far, the weakest known force in the universe.
引力是目前为止，宇宙中已知的，最弱的力。
You can see that because it's really easy for me to pick a rock up off the ground,
从地上捡起一块石头，我很容易做到，
even though there's a whole planet, Earth, pulling the rock down.
即使是整个地球，拽着石头下来。
I can just lift it up.
我也能把它拿起。
Incredibly weak,
令人难以置信的，弱！
but incredibly important, because it's the only force there is
但很重要的是，它是唯一能够
to hold an atmosphere to the planet.
维持住地球的大气层的力量
The more massive the planet, the greater its gravitational force.
越是庞大的星球，它的引力就越大。
Earth has enough mass to keep a tight grip of the gas molecules that make up our atmosphere.
地球有足够的质量，严格控制住气体分子，以维持大气层
It holds them against the surface and allows us to breathe.
使我们能够呼吸。
Now, we don't really notice the presence
现在，我们真的无法发现
of our atmosphere, I suppose, because we live in it, all the time.
大气层的存在，我想，“只缘身在此山中”。
But there's a lot of it.
但是它有很多。
There's five million billion tons of air surrounding the Earth.
地球上，有5000万亿吨的空气。
That's the equivalent of a weight of one kilogram
这就等价于有一公斤的重量
pressing down on every square centimetre of our bodies.
压在我们每平方厘米的皮肤。
Or, put it another way, if I'm about a metre square,
或者，换一种方式，如果我有一平方米，
that's ten tons of weight pressing down.
就有10吨的重量压着我。
Now I say pressing down, but that's not entirely right,
现在我说压下，但这并不完全正确，
that's not how air pressure works.
这不是气压的工作方式。
It presses in every direction at once. I can demonstrate that.
它压向任何方向。我可以证明这点。
This is a glass full of water,
这是一杯水，
so if I put a piece of paper on there, turn it upside down.
如果我把一张纸放在那里，倒过来。
Now, if I'm right, then the air pressure is pushing
现在，如果我是对的，空气压力
in every direction on this glass of water, the air pressure is pushing up as well as down.
压向任何方向，在这杯水，也能向上压。
And it has no problem in holding the water in the glass.
一切OK
Cool.
帅。
Where did you get this water from?
这水哪里来的？
...
CREW LAUGH
Life on the surface of this planet survives,
生命在这个星球上生存了下来，
surrounded by this enormous mass of gas. We're like lobsters,
我们就像龙虾，被这些巨量的大气包围住，
scuttling around on the ocean floor.
在海底，搞搞震。
But our atmosphere does more than allow us to breathe.
大气，不仅让我们呼吸。
It protects us
还保护着我们
from the most powerful force in the solar system...
来自太阳系中，最强大的力量，
..our sun.
..我们的太阳。
If you ask yourself the question, "Why is Earth
如果你问下自己，“为什么
"the temperature that it is?"
“地球的温度就这么好？”
Then, the obvious answer might seem to be,
答案似乎很明显，
"Well, because it's 150m kilometres away from the sun".
“嗯，因为太阳离我们1.5亿公里嘛。”
But actually, things aren't quite that simple.
但实际上，事情没有那么简单。
This is the Namib desert in Namibia, in south-western Africa.
在西南部非洲，纳米比亚的纳米布沙漠中，
And as the sun sinks below the horizon, the temperature change,
当太阳落山，温度就变了，
from day to night, can be as much as 30 degrees Celsius.
从白天到夜晚，温差高达30摄氏度。
That's an immense amount in just a few hours,
这是一个巨大的数值，在短短几个小时里，
much more than in somewhere like Manchester, for example.
相对于其他远方，例如像曼彻斯特。
The reason is that this is also one of the driest places on the planet
原因在于，这里是地球上最干燥的地方之一，
and so there is very little water vapour in the atmosphere.
所以大气中很少有水蒸气存在。
That means that the atmosphere is not a very good insulator,
这说明，大气不是很好的绝热体，
so when the sun disappears, the heat just disappears quickly into space.
所以当太阳消失，热量也迅速消失散出太空。
Now, there's a planet in the solar system,
现在，太阳系有一颗星球，
somewhere over there, near the sun,
在那里的某个地方，靠近太阳，
where the temperature shift, from day to night,
从白天到夜晚，温度一直变化，
is not a mere 30 degrees Celsius, but an immense amount bigger.
不只相差30摄氏度，而是更巨大的数值。
Roughly 58 million kilometres from the sun
大约离太阳5800万公里的地方
is the smallest planet in the solar system...
太阳系中...最小的行星
..Mercury.
..水星。
This tortured piece of rock
烤焦的石头
suffers the biggest temperature swings of all the planets,
它接受着最高温度的折磨
from 450 degrees Celsius in the day,
从白天的450摄氏度，
to minus 180 degrees at night.
到晚上的零下180度。
And all because Mercury has been stripped naked.
一切的原因都是它没穿衣服
It has virtually no atmosphere at all.
实际上它一点大气都没。
Like all the rocky inner planets of the solar system,
像其他太阳系的岩石内行星
Mercury had an atmosphere when it was formed,
当水星形成时，它有一个大气层，
but it lost it very quickly.
但它很快就失去了。
Here on Earth,
在地球这里，
at sea level, then...
在海平面，然后...
Well, in a volume about the size of this pebble,
大概，一个小卵石的大小，
there are 10 billion billion molecules of gas.
就有1000亿亿个气体分子。
On Mercury, in the same volume, there would be around a 100,000,
水星，相同的体积只有10万个左右，
that's 10 million million times less.
少了10万亿倍。
Now, planets hang on to their atmosphere by the force of gravity.
现在，大气被行星的引力束缚。
It's the only way they can
这是它们唯一的方法来阻止
stop that thin blue line of gas disappearing off into space.
这种蔚蓝色大气逃逸到宇宙中。
So, the bigger the planet, the more massive the planet,
所以，越大的星球，
the stronger the gravitational pull and the easier it is for the planet to keep hold of its atmosphere.
引力就越大，就越容易束缚它的大气层。
So, Mercury was just too small and too hot to hang onto its atmosphere
因此，水星太小，太热，控制不了它的大气层
and the consequences for the planet were absolutely devastating.
结果就是非常的悲剧。
Atmospheres may be just a thin strip of molecules,
大气层只是薄薄的分子带，
but they are a planet's first line of defence.
但它们却是地球的第一道防线。
Without them, a planet like Mercury
没有它们，就像水星一样。
is at the mercy of our violent solar system.
祈求太阳的怜悯。
This is Saskatchewan in western Canada and it is a cold place to be in November.
这里是萨斯喀彻温省，加拿大西部，这里的11月很寒冷。
About a year ago, in November 2008, a piece of asteroid,
大约一年前，2008年11月，一颗小行星，
a space rock, weighing about ten tons,
太空里的石块，重约10吨，
entered the atmosphere right over here and actually landed
撞入大气层，降落在约30公里外，
about 30 kilometres that way, at a place called Buzzard Coulee.
一个叫巴扎德古力的地方。
Now, it's not unusual for rocks that big to hit the Earth.
它不过是一块撞上地球的普通石头
On average, that happens about once a month.
平均而言，这种情况大概每月一次。
What was unusual about this one was that it was over quite a densely-populated area.
不寻常的是，这里是人口密集的地区。
So tens of thousands, if not hundreds of thousands, of people saw it and heard it.
因此，成千上万，甚至是数十万的人看到或听到它。
But most spectacularly, it was captured by a lot of CCTV cameras,
最引人注目的是，它被监控镜头拍到了，
including that one, in this garage.
其中，包括这个，车库上的。
These are the actual CCTV images captured around the city.
这些都是真实的监控镜头，
They show the meteorite,
它们表明，一块陨石，
as it streaked across the sky at 20 kilometres per second.
以每秒20公里的速度划过天空。
The fireball was brighter than the moon and turned the night sky blue.
这明亮的火球使月球为之黯然，夜空变成蓝色。
Scientists used these remarkable images
科学家使用这些图像
to triangulate the impact site of the meteorite.
通过三角函数，算出陨石的撞击地点。
They traced it to a field, just outside the city of Lloydminster.
他们追踪到一个地方，就在劳埃德明斯特市外。
A team of meteorite hunters have been searching the debris left by the enormous explosion.
一个陨石猎人队一直在寻找当时爆炸的碎片。
They are led by Dr Alan Hildebrand.
他们由Alan Hildebrand博士领导。
How much energy
携带了多少能量
does a rock like this have, then?
像这样的石头，嗯？
You know, what is it, a ten-ton rock travelling at 50 times the speed of sound?
嗯，一块10吨重的石头以50倍的音速飞行？
You know, it would be like if you'd stocked up,
啊，这相当于，
400吨TNT当量。
say, 400 tons of TNT to explode.
I mean, it's really quite dramatic.
我的意思是，这真的很戏剧性。
400 tons that just dissipates away in the Earth's atmosphere? Yes.
400吨，就这样散失在大气层？是。
Atmosphere slowing it down, of course, causing it to break up.
大气层放慢了它的速度，当然，导致它破碎了。
In just five seconds, it's almost all over and, of course,
短短5秒钟，它几乎都烧完了，当然，
you know it's an extreme friction, makes the light show.
你知道这是一个极端的摩擦过程，像灯光表演。
10% of the energy goes in light and it's like a billion-watt bulb shining high in the sky.
它用10％的能量点亮了夜空，就像一只10亿瓦的灯泡
So, what are we looking for?
那么，我们寻找什么？
What does a piece of that asteroid look like?
陨石碎片是长什么样的？
They... Going through the atmosphere,
它们...通过大气层，
the surface has got melted, so you end up with a dark crust on them.
表面已经融化了，所以你最终看到它们黑暗的外壳。
So, essentially, you're looking for an oddly-sculpted dark rock.
所以，基本上，你要寻找的是一块奇怪的，黑暗的石头。
Yeah. Well, in all fairness, you've got to be able to tell it from, you know the cow patties and so on.
是啊。没吃过猪肉，也见过猪跑吧。
But... I could probably manage that.
但是...我希望能做到吧。
Once you get your eye in, you'll have no trouble.
你看见了，也没事的。
We've got one right here.
找到一个啦。（好假- -！）
I'll pick that up.
捡起来先。
Astonishing.
令人惊讶。
It's just been completely rounded off.
很圆润。
Yeah, the heat melted the surface of the rock.
是啊，热量融化了岩石的表面。
I mean, how hot does something have to be to do that? Yeah.
我的意思是，要多热才能做到这一点？恩。
6,000 degrees C would do it.
6000度才得。
So, this little rock has had an amazing history.
所以，这个小石头有惊人的历史。
I mean, it approached Earth as part of this bigger fragment,
我的意思是，它接近地球时块头很大
at about, what, 18, 19, 20 kilometres per second.
约，每秒20公里的速度。
It hit the Earth's atmosphere.
撞入地球大气层。
About 85 kilometres up, it began to feel the effects
大概85千米以上，它开始受到
of the Earth's atmosphere.
地球大气层的影响。
It began to squash the air in front of it, creating a pressure wave,
它开始冲击前面的空气，创造了压力波，
essentially, which, in turn, causes this thing to heat up.
实质上，这反过来，导致它升温。
And it would have heated up to something like the temperature of the surface of the sun.
它会加热到太阳表面的温度。
It would have been 5 or 6,000 degrees Celsius as it plummeted through the atmosphere,
也许是5或6000摄氏度，因为它通过大气，
lit up the sky over here and then, quite literally,
在这里照亮了天空，然后，毫不夸张地说，
exploded in a series of explosions and peppered these fields with lumps of rock this big.
发生了一系列爆炸，散落碎片到这片区域。
Can you imagine standing here on that night and having this, these things -
你能想象站在这里，晚上会有这些东西 -
and this is heavy, right -
如此沉重的，是的 -
raining down from the sky?
从天上落下来？
It must have been quite incredible.
真是匪夷所思。
If the meteorite had hit the ground intact,
如果陨石直接击中地面，
the explosion would have been been equivalent to 400 tons of TNT
能量相当于400吨的TNT当量，
and left a crater 20 metres wide.
炸开20米宽的陨石坑。
The Earth was spared this colossal impact by nothing more
地球没受影响，恰恰就是
than the tenuous strip of gases that surrounds us.
这层我们周围脆弱的大气层
But not all planets have this protective blanket.
但是，并非所有的行星都有这种保护毯。
When a meteorite hits naked Mercury,
当陨石击中裸体水星，
there is no atmosphere to break it up or slow it down.
没有大气使它破碎或慢下来。
It strikes the ground at full speed and completely intact.
它完好无损直接全速击中地面。
For the last 4.6 billion years,
过去46亿年里，
Mercury has been bombarded with countless asteroids and comets.
水星一直被无数的小行星和彗星轰炸。
The whole history of the planet's violent past is laid out on its surface,
整个行星的悲剧史，奠定了其表面，
a world pitted with hundreds of thousands of craters.
几百几千的陨石坑的世界。
Craters inside craters, inside craters.
陨石坑中的陨石坑，陨石坑中的陨石坑。
Mercury was damned from the start.
水星一开始就悲剧了
It's simply too small and too hot
它太小，太炎热了
to have retained any meaningful traces of atmosphere.
没有任何能保留大气的证据。
We, on the other hand,
我们，另一方面，
are big enough and cold enough
足够大也足够冷
to have retained this envelope of gases.
足以保留下气体。
That, in turn, allows
反过来，
living things, like me, to evolve
有生命的东西，像我一样，去演变
and to use that atmosphere, to breathe and to live.
并利用这里的大气，呼吸和生活。
But there are places out there in the solar system
但在太阳系，某些地方
whose atmospheres have the same ingredients as our own,
它的大气层成分跟我们一样，
but when the formula is even slightly remixed,
但是，公式即使是轻微的改变，
it leads to worlds that couldn't be more different.
世界也将完全不同。
Roughly 108 million kilometres from the sun
大约离太阳一亿八百万公里，
sits the brightest planet in the solar system, Venus.
太阳系中最亮的行星，金星。
This footage shows the luminescent world appear
画面显示出，这个发光的世界
from behind our cratered moon.
从月亮背后出现。
Venus and Earth share many similarities.
金星和地球有许多相似之处。
We sit next to each other in space,
我们坐落在相邻的空间，
we were formed from the same material
我们是同样物质的构造
and we're roughly the same size and share a similar mass and gravity.
大致相同的体积，相似的质量和引力。
But that's where any similarities end.
但是，相似之处到此为止。
Venus is a tortured world,
金星是一个备受折磨的世界，
where thick clouds of sulphuric acid are driven along by high winds
大风之下，翻滚着浓浓的硫酸云
and temperatures are hot enough to melt lead.
温度高得足以将铅熔化。
All because this planet's atmosphere created a runaway greenhouse effect.
因为这个星球的大气层，温室效应严重失控。
The "greenhouse effect" has become a well-known phrase.
“温室效应”已成为众所周知的词语。
You know, it's synonymous with global warming.
它的代名词就是全球变暖。
But what is it?
但究竟是什么？
Well, a planet, like the Earth, absorbs energy from the sun as visible light.
一颗行星，像地球，从可见光中吸收太阳的能量
Now, atmospheres don't absorb much visible light, as you can see, because you can see the sun.
大气无法吸收太多的可见光，所以你可以看到它们。
The ground absorbs the visible light, heats up and then re-radiates it.
地面吸收可见光，升温，然后重新辐射。
But it re-radiates it as infrared radiation, heat radiation, if you want.
但重新辐射，是作为红外辐射，热辐射的形式。
And atmospheric gases, particularly carbon dioxide, are very good
而大气中的气体，尤其是二氧化碳，非常能
at absorbing in the infrared and so they trap the heat and the planet heats up.
吸收红外线，所以它困住了热量，使地球变暖。
On Earth, greenhouse gases are essential to our survival.
地球上的温室气体，对我们的生存是必不可少的。
Without them our planet would be 30 degrees colder,
没有它们，我们的星球将寒冷30度，
too cold to support life as we know it.
太冷就难以维持生命了，我们都知道。
But Venus's atmosphere was flooded with greenhouse gases.
但金星的大气，被温室气体淹没。
The nearby sun slowly boiled away its oceans,
附近的太阳，慢慢地煮沸它的海洋，
pumping water vapour into the atmosphere.
抽取水蒸汽到大气中。
And carbon dioxide, from thousands of erupting volcanoes,
二氧化碳，从数以千计的火山爆发出来，
added to the stifling mix.
加入到这个恐怖的组合。
Venus grew hotter and hotter.
金星变得越来越热。
The planet was slowly choked to death.
该行星慢慢地窒息，死亡。
Venus is a planet with an atmosphere in overdrive,
金星是一颗大气过多的行星
but Earth's other rocky neighbour tells quite a different story.
但地球其他的岩石邻居，又有另一番故事。
Get it!
成功！
These are the dunes in the Namib desert.
这里是纳米布沙漠
It's an absolutely spectacular place.
这是一个绝对壮观的地方。
This place is not the hottest,
这个地方不是世界上最热，
nor the driest, desert in the world, but these dunes
最干旱的荒漠，但这些沙丘
are some of the oldest sand dunes in the world.
都是地球最古老的沙丘之一。
And the reason we're here in the Namib desert
我们之所以来到纳米布沙漠
is that this is a great analogue
是，为了一个伟大的模拟
for the surface of Mars.
火星地表。
This is what the surface of Mars looks like and these dunes,
火星地表看起来就像这些沙丘，
called barchan dunes, these crescent-shaped dunes,
称为弧沙丘，这些新月形沙丘，
are the same as the sand dunes on Mars.
跟火星上的沙丘，是一样的。
So, if you want to get a feel for what it would be like on the surface of Mars,
所以，如果你想感受下火星表面
and you want to know what driving a 4x4 around on it would be like, then this is the place to come.
你想知道火星表面驾驶的快感，这里是不错的选择。
Incredibly, there is a vehicle driving across the surface of the "red planet" today...
令人难以置信的是，如今，有一辆行驶在...
..a space rover, named Opportunity.
..“红色星球”地面的空间探测车，机遇号。
The rovers and spacecraft that circle the planet
该探测器和飞船环游了火星
have sent back images which reveal Mars in exquisite detail.
它发回的图像，精致的细节揭示了
Mars has vast dunes,
火星上有巨大的沙丘，
enormous volcanoes
巨大的火山，
and giant ice sheets.
和巨大的冰盖。
It has canyons and river valleys.
它有峡谷，有河谷。
Mars is a dry, frozen version of our home, covered in red dust and sand.
火星干燥，冰冷，覆盖着红色沙尘。
And it's all due to the fact that Mars has virtually no atmosphere.
这一切都缘于一个事实，火星上几乎没有大气层。
But there are clues
但也有线索表明
that things weren't always this way.
事情并不总是这样。
These are pictures taken from the surface of Mars in August 2009.
这些都是从火星表面拍摄的照片，2009年8月。
And they caused quite a bit of excitement, because of this,
很多人因此兴奋不已，因为这个，
this rock sat on the surface of Mars in front of the rover.
这块躺在地面的石头，火星探测车的前面。
This rock is about...
这块石头是有关...
Well, here's a close-up.
嗯，有一个特写镜头。
It's actually a nickel iron meteorite
它实际上是镍铁陨石
and it's about, what, 60 centimetres across,
大概它有，60厘米宽，
weighs half a ton.
重达半吨。
It came from space,
它来自太空，
came through the Martian atmosphere and landed on the ground.
闯过火星大气，落在地面上。
But the mystery is that a meteorite this big, if it hit Mars today,
但神秘的是，这个大陨石，如果它今天击中火星，
would disintegrate when it hit the surface.
当它击中地面就会崩碎开，
It would be travelling too fast and that's because
速度太快了，
Mars's atmosphere is too thin, too diffuse to slow it down.
由于火星大气层太薄，无法削减它的速度。
But that meteorite is very definitely there
但是，陨石很明显就在那里
so how could it have made it to the ground?
它怎么会在地上的？
Well, it must be that, in the past, when this meteorite hit Mars,
好，它肯定，在过去，当它撞击火星，
Mars' atmosphere was significantly denser,
火星大气非常稠密，
dense enough to slow this piece of rock down enough
足以减慢了这块石头
that it could land on the surface intact.
使它可以表面完好无损地落地。
But why did Mars lose its thick atmosphere and become the barren planet we see today?
但为什么火星失去了厚厚的大气，成为今天看到的贫瘠星球？
There are so many ways for planets to lose their atmospheres
有很多方式使行星失去大气，
that it feels like a miracle that we've still got ours.
感觉就像一个奇迹，我们今天仍然有我们的大气层。
But with Mars, it's thought that one of
但火星，认为其中一个主导因素
the dominant mechanisms was interaction with solar winds.
是与太阳风的相互作用。
The solar wind is a stream of super-heated, electrically-charged particles
太阳风是过热流，带电粒子流
that constantly stream away from the sun at over one million kilometres per hour.
持续不断地，以超过百万公里的时速远离太阳。
This wave of smashed atoms has the power to strip a planet of its atmosphere.
这种极强的原子波足以撕裂行星的大气。
On Earth, we're protected from this onslaught by an invisible shield
地球，我们受一个无形的盾牌保护，免遭攻击
that completely surrounds our planet, known as the magnetosphere.
我们称之为地球磁层。
The magnetosphere is created deep within the Earth's molten iron core.
磁层由地球熔化的铁核心形成。
As the core spins, it generates a powerful magnetic field
核心旋转时，它产生一个强大的磁场
which shoots out of the pole and cocoons the whole planet.
贯穿两级，包裹整个地球。
This magnetic shield is strong enough to deflect most of the solar wind that comes our way.
这就是磁屏蔽，强大到足以偏转太阳风。
Now, we know that at some point in the past, Mars
现在我们知道，在过去某个时候，
would also have had a molten core and did have a magnetic field.
火星也有一个熔化的核心，也有磁场。
But because Mars is a smaller planet than the Earth,
但是，因为火星是一颗比地球小的行星，
it lost its heat more quickly and the core solidified.
它失去热量更迅速，核心也固化了。
Electric currents could no longer flow and its field vanished.
电流不再流动，磁场也消失了。
And that was a major factor in the solar wind being allowed to
这是一个主要因素，使得太阳风
blast the planet and strip away its atmosphere.
可以冲击星球，剥离它的大气层。
With no atmosphere to insulate it, this once Earth-like world
如果没有大气的隔离，地球将变成
transformed into the frozen desert we see today.
我们今天看到的冰冻沙漠的世界。
A shadow of its former self.
火星的另一个版本。
Although Mars has lost most of its atmosphere,
虽然火星已经失去了大部分的大气，
those few molecules that remain still have the power to sculpt and transform the surface.
但残留的气体分子仍有塑造和改造地表的能力。
And that power, that transformative effect,
这种能量所变化的影响，
is present on every planet in the solar system that has an atmosphere.
存在于太阳系每一颗有大气的行星。
You can see it transforming the surface of the Namibian desert today as we speak.
你可以看到它改变了纳米比亚沙漠的地表。
It is, of course, the force of nature that we call weather.
这是，当然，该自然力量，我们称之为天气。
We've got to go. Wow!
我们得走了。哇！
Weather is a feature of every planet with an atmosphere.
天气是每一颗星球大气的特征。
Our world is transformed as this huge mass of air moves across its surface.
我们的世界由于巨量的空气而改变。
But as we look out into the solar system,
正如我们看到的太阳系，
we see it only takes the slightest atmosphere to produce extraordinary weather.
它只需一丝的大气就能产生非凡的天气。
Every few years, Mars all but disappears under a maelstrom of dust.
每隔几年，火星就会消失在尘埃漩涡之下。
Global dust storms are so huge they dwarf Olympus Mons,
全球沙尘暴大到以致奥林匹斯（名字）显得如此之矮，
a volcano three times bigger than Everest.
一座比珠穆朗玛峰大三倍的火山。
But to experience the most extreme and violent weather in the solar system,
但是，为了体验在太阳系，最极端暴力的天气
we need to travel to Jupiter.
我们需要前往木星。
This banded gas giant is over 140,000 kilometres in diameter.
这个带状巨型气旋直径超过14万公里。
Its atmosphere isn't a thin blue line, it's many thousand of kilometres thick
它的大气不是薄薄的蓝色，而是厚达数千公里
and in a constant state of seething motion.
恒定不变的翻腾着
The whole surface boils with gigantic storms.
整个表面都翻滚着巨大的风暴。
Yet, this most alien world shares a feature with our own planet.
然而，这个最大的陌生世界和我们的星球有着共同的特征。
RUMBLING
Jupiter crackles to the sound of electrical storms.
木星电气风暴产生的裂纹声音
The bolts of lightning are thousands of times brighter than lightning here on Earth.
这里的闪电比地球上的光亮数千倍
The physics of storms on Jupiter is, of course, the same as the physics of storms on Earth.
木星风暴的物理学，当然，跟地球上的风暴一样。
The warm moist air deep in the atmosphere starts to rise, and as it rises it cools.
温暖潮湿的空气在大气中上升，并冷却。
And the moisture condenses out to form clouds.
水分凝结出来，形成云。
Now, that rising air leaves a gap beneath it, a low pressure area,
现在，上升气流留下一个缺口，一个低压区，
and so more warm, moist air is sucked in and that fuels the rise of the storm.
所以更温暖，潮湿的空气被吸进去，加速风暴的形成。
Now, on Earth, those storm systems are driven by the power of the sun.
现在，地球上那些风暴系统是由太阳的力量驱动的。
But therein lies a mystery because the storm systems on Jupiter are far more powerful
但这留下一个谜团，因为木星的风暴更强大
and yet Jupiter is five times further away from the sun than the Earth is,
但木星离太阳比地球远5倍，
which means it receives 25 times less solar energy.
这意味着它接收太阳能少了25倍。
So, what mechanism could it be that powers those intensely violent storms on Jupiter?
是什么原理使木星上的风暴如此劲爆？
The secret to Jupiter's storm-tossed atmosphere lies hidden deep within the gas giant.
木星风暴的秘密深深隐藏在它的大气里。
On Earth, we have clear boundaries between the gaseous sky,
在地球，我们有明确的分界线，
the liquid oceans and the solid ground.
气态天空，液态海洋和坚实的地面。
But on Jupiter, there are no such boundaries.
但在木星，没有这样的分界线。
It's a gas giant, made of the two lightest and most abundant elements in the universe,
这是一颗巨大的气体行星，由宇宙中最轻和最多的元素构成
hydrogen and helium.
氢和氦。
But as you go deep into Jupiter's atmosphere,
但是当你深入到木星大气层里，
something very strange and interesting happens to those gases.
这些气体发生了一些很奇怪很有趣的事。
Jupiter's atmosphere is so thick and its gravitational pull so strong
木星的大气层是如此厚重，它的引力如此强大
2万公里云端下方，
that 20,000 kilometres beneath the cloud tops,
the pressure is 2,000,000 times greater than the surface pressure here on Earth.
压力为两百万倍于地球的表面。
Under such immense pressure, the hydrogen gas in the atmosphere
这样巨大的压力，使大气中的氢气
is transformed into a strange metallic liquid.
转化成一种陌生的金属液体。
As the gases are squeezed, a vast amount of energy is released,
由于气体压缩，大量能量释放，
enough energy to fuel some of the biggest storms in the solar system.
足以点燃太阳系中最大的风暴。
The biggest of them all is the Great Red Spot.
它们中最大的是，大红斑。
This giant anti-cyclone has raged for hundreds of years
这巨大的逆转气旋已经持续数百年
and is large enough to swallow the Earth three times over.
大到足以吞下地球的3倍以上。
The Great Red Spot is an awesome sight.
大红斑是一个绝妙的景象。
But this giant isn't one of my wonders.
这个巨斑我并不惊奇。
My wonder is a much smaller world.
我惊奇的是一个小得多的世界。
A moon that orbits the gas giant Saturn, 1.5 billion kilometres from Earth.
巨型气体土星的卫星，离地球15亿公里。
What we have found on this small world is simply astonishing.
我们发现这个小世界极为惊人。
If you thought of our moon as the archetypal moon of the solar system, if you like,
如果你认为我们的月球，是太阳系卫星中的典型，
then... Well, you might think that all the other moons out there,
那么，你可能会认为所有的其他卫星，
hundreds of them, would be dead, uninteresting worlds.
数以百计的，都是死气沉沉，无趣的世界。
I mean not uninteresting places to visit.
我的意思不是探访它们很枯燥。
I mean that is, in my view, the greatest thing that humans have ever achieved,
我的意思是，在我看来，人类曾经实现的最伟大的事，
landing on the surface of the moon but it's a dead and lifeless place.
登陆月球，但它是一个毫无生机的地方。
But as we've begun to visit those worlds, as we've flown spacecraft
但是当我们开始探访那些世界，当我们飞船飞行到
to within hundreds of miles of their surfaces, we've found that the moons in the outer solar system
它们数百英里的上空时，我们发现在太阳系外域的卫星
are of an astonishingly interesting and varied and fascinated bunch of worlds.
是惊人的有趣的和多元化的，令人着迷的世界。
This is Jupiter's moon, Europa.
这是木星的卫星，木卫二。
This is Jupiter's moon, Io, the most volcanic object in the solar system.
这是木星的卫星，木卫一，太阳系中最多火山。
But of all the worlds out there, this one - Saturn's moon, Titan - is unique, because of that.
但是，这个 - 土星的卫星，土卫六 -
That is an atmosphere, and what an atmosphere it is!
如此独一无二。因为这是一层大气层，这是怎样的一层大气啊！
It's 1,000 kilometres deep, it's four times denser than the atmosphere of the Earth.
它有1000公里深，密度4倍于地球大气层。
I mean imagine that,
我的意思是。想像一下，
a moon around a distant planet in the icy, distant reaches of the solar system
在太阳系冰冷，遥远的地方，一颗绕着行星转的卫星
with an atmosphere denser and thicker than our own.
有一层大气，密度厚度都比我们的高。
Titan has the most Earth-like atmosphere in the entire solar system,
土卫六拥有整个太阳系中，最类似地球的大气层，
a thick blue line, rich in nitrogen and containing methane.
一个厚厚的蓝色线，含有丰富的氮和甲烷。
At first sight, a world this small shouldn't be able to hold onto such a dense atmosphere,
乍一看，这个小世界应该不能束缚如此浓厚的大气，
except Titan lies in one of the coldest regions of the solar system,
除了土卫六是太阳系最冷的地区之一，
and that makes all the difference.
所有的一切都使它与众不同。
Temperature for gases like this, the gases in our atmosphere,
气体的温度，
is really a measure of how fast the molecules of the gas are moving around,
是衡量气体分子移动速度的尺度，
and I can demonstrate that with this thing, which is a Chinese lantern.
我可以示范，这个是中国彩灯（孔明灯）。
If I light this fuel,
如果我点火，
then what's going to happen...
会发生什么呢...
is that the gas inside is going to heat up.
内部气体将升温。
And as you heat up a gas,
当你加热气体，
what that basically means is that you speed all the molecules up.
意味着，你基本上加速了所有的分子运动。
As the molecules of air heat up and move faster,
当空气分子加热，运动更快时，
the air pressure inside the lantern begins to increase.
灯笼里面的空气压力开始增加。
That means that molecules are forced out, making the air inside less dense than the air outside,
意味着，分子要冲出去，使内外压力平衡，
and the lantern gets lighter.
灯笼变得更亮。
And eventually the lantern is so light...
最终孔明灯变得很轻...
..that it will just float away in the atmosphere of our planet.
..它漂浮在我们地球的大气层。
Hot gases have more energy to escape a planet's gravitational pull than cold gases.
热气体比冷气体有更多的能量去克服行星的引力。
Now Titan is a much smaller body than the Earth. It has much weaker gravitational pull,
土卫六比地球小。它的引力更弱，
and if it were in the same region of the solar system as we are,
如果它在太阳系的位置跟我们一样，
then it would not be able to hold onto its atmosphere.
那就不能束缚它的大气层。
But it's a lot further away from the sun than we are
但它离太阳比我们远得多
and so that means that it's colder, its atmospheric molecules are moving around much more slowly than ours.
意味着，它更寒冷，它大气分子的移动比我们更慢。
That means that its weak gravity is enough to hold on to that thick dense atmosphere.
于是它这么弱的引力也能束缚这么厚密的大气
Titan's thick atmosphere was an unexpected discovery,
土卫六的大气层是一个意外的发现，
but it took an audacious mission
但它肩负了伟大的使命
to reveal the world that lies beneath the blanket of clouds.
去揭示了云层下的世界。
We have lift off of the Cassini spacecraft on a billion-mile trek to Saturn.
我们已经升空，去往土星的卡西尼航天器。
1997年，卡西尼号去往土卫六的旅程开始。
In 1997, Cassini began its journey to Titan.
It carried with it the Huygens probe, a lander designed to set down on this frozen moon.
它载着惠更斯探测仪，一个发射到这冰冻卫星的着陆器。
2004年圣诞节，
On Christmas Day 2004,
Huygens was released from Cassini and it began the bumpy ride
卡西尼释放出惠更斯，它开始颠簸着
through one of the most intriguing atmospheres in the solar system.
通过太阳系中最迷人的大气层。
And then, for the first time,
然后，第一次，
the thick clouds parted and the surface of Titan was revealed.
土卫六厚厚的云层开始消散。
These are the actual images taken by Huygens
这些是由惠更斯拍摄的实际图像
as it slowly parachuted to the surface.
当它慢慢降落到地面。
The world it revealed
这个世界比我们想像到的更熟悉。
was more familiar than we could have possibly imagined.
One of the first people to see
其中首先看到的
these incredible images was a man who helped design the probe,
是一位帮助设计探头的专家，
Ralph Lorenz.
拉尔夫洛伦兹。
It was amazing because we just had no idea what to expect.
这是惊人的，因为我们不知道会发生什么。
We didn't know whether it would be, you know, cratered like the moon or just sort of a flat expanse of sand
我们不知道它是什么样子
and then these first pictures came back and it was just astonishingly familiar.
当第一批照片返回来，却惊人的熟悉。
Did that picture, that initial series of pictures...
这系列最初的图片...
I suppose it did look somewhat like this, didn't it? It did.
我想这确实看起来有点像这里，不是吗？是的。
It could have been there. It could have been right here. I do see that.
它可能是那里。它也可能在这里。我也看到了。
I could sit here,
我可以坐在这里，
look at that and that's what that picture looks like.
看的，这就是该图片的模样。
I could take it with a camera.
我可以用照相机拍了。
The camera on the probe was about the height of your knee, so yeah,
探测器上的摄像机大概是你膝盖的高度，恩是的，
the view the Huygens probe had is just like this.
惠更斯探测器的视野就是这样。
Rounded stones dot the landscape.
圆形石头的风景点。
They're smooth and look like they have been eroded by tumbling water,
它们看起来好光滑，像是被水打磨过，
similar to stones found on river beds, here on Earth.
类似在地球上，河床发现的石头。
It sounds to me like this was one of the easiest pictures to interpret
我听起来这是最简单的图片解释
in the history of space exploration.
在空间探索的历史里。
You know, the way you tell it, it's just that's a river bed with these stones. I mean, is it that simple?
它的只是河床的石头。就这么简单？
Because you can be misled easily, with...
因为你可以很容易受到误导，与...
The devil is always in the details,
细节是最麻烦的
but I think there were very few people
但我想只有极少数人
disputed the interpretation of a river channel.
才会争论。
I mean it's just such a familiar thing to so many people on Earth, there really wasn't much doubt.
我的意思是，人尽皆知的事，不会有很大的疑问。
It was an extraordinary discovery.
这是一个惊人发现。
Evidence of flowing rivers had never been found before on a moon.
有证据的河流，以前从来没有在卫星上发现过。
But it wasn't the only surprise Titan held in store.
但它不是土卫六唯一的惊喜。
This is the Matanuska glacier in Alaska.
这是马塔努斯卡冰川，在阿拉斯加。
It really is one of the most astonishing places I've ever seen.
这真的是我见过最令人惊讶的地方之一。
And this whole landscape is testament to the erosive power of this stuff,
这整个景观证明了，这个东西的侵蚀性，
this mixture of ice and rock
由冰和岩石组成的混合物
as it rolls down this valley over hundreds of thousands of years
数百数千年，它在这个山谷滚下来
and creates this astonishing landscape.
并创造了这个惊人的景观。
But the reason it can do that
但是，它之所以能够做到这一点
is because of the delicate balance of the Earth's atmosphere.
是因为地球大气层微妙的平衡。
You see, our planet is just at the right temperature and pressure to allow water to exist as solid,
你看，我们的地球只不过是在适当的温度和压力
as liquid and as gas, as vapour in the clouds.
让水存在于固体，液体和云中的气体。
And so the sun can heat up the oceans and it can move the water over the top of the mountains.
所以太阳可以加热海洋，将水托到山的顶部。
It can fall as rain, turn to ice, become a glacier
它可以下雨，变成冰，成为冰川
and then sweep down the valley to sculpt this astonishing landscape.
然后从山谷滚下来，形成这惊人的景观。
Just as our atmosphere allows all this to exist,
正如我们的大气层让这一切的存在，
the atmosphere of Titan is the perfect temperature and pressure to allow something to exist
土卫六的大气层，也有完美的温度和压力
that has never been seen before on a world beyond Earth.
存在着地球以外从未见过的世界。
This is a picture taken of the south pole of Titan
这是土卫六的南极
by Cassini in June 2005,
卡西尼号在2005年6月拍摄，
and it's become one of the most important and fascinating pictures
它已经成为其中最重要的迷人的图片
in the history of space exploration.
在太空的探索历史。
The interesting thing is this black blob, here.
有趣的是这个黑色的斑点，在这里。
Now this fascinated the Cassini scientists but the explanation as to what that is
卡西尼的科学家很好奇，但合理的解释
had to wait just over a year till July 2006,
却等待了，超过1年，直到2006年7月，
when this picture was taken,
当这张照片
and it's a radar image, this time of the north pole of Titan,
它的雷达图像，这一次是对土卫六北极的拍摄，
and you see, again, these huge black areas.
你看，再次的，这些巨大的黑色区域。
The black in this case means that the radar waves that bounced onto them didn't come back
在这种情况下，黑区域代表雷达波没有返回
so they're completely black, and there's only one really good explanation for that.
所以它们完全黑暗，真的只有一个合理的解释。
That is that they are incredibly flat surfaces.
它们很平坦的表面。
In fact, they're surfaces of liquid
事实上，它们是液体的表面
so this picture combined with this picture
所以这张图片结合这张图片
means that this is the first observation of a liquid,
也就是说，这是第一次观察到液体，
a lake on the surface of a body other than the Earth in the solar system.
一个湖，在地球以外的太阳系。
But these lakes, of course, cannot be lakes of liquid water because
当然，这些湖泊不是液态湖泊，
the surface temperature on Titan is minus 180 degrees Celsius and, at those temperatures,
因为土卫六表面温度是零下180摄氏度，
water is frozen as hard as steel.
这样的温度，水冰冻后都坚硬如钢。
So if these are not lakes of water, then what are they?
所以，如果不是液态湖泊，那么它们是什么？
This is Lake Eyak in Alaska, just on Prince William Sound,
这里是阿拉斯加埃亚克湖，威廉王子湾，
and I've come here to collect a molecule or a substance that's very abundant on Titan.
我这次来收集一些分子或物质，土卫六上非常丰富的东西。
In fact, it's abundant throughout the solar system, but here on Earth
事实上，太阳系里都很丰富，但在这里，地球上
it exists as a gas and it bubbles up from the floor of this lake.
它以气体存在，从湖底冒出。
The floor of Lake Eyak is covered in rotting vegetation, you know, dead leaves and bits of trees, twigs,
埃亚克湖地面覆盖着腐烂的植物，死叶和树木，树枝，
and that's been broken down by bacteria which produce the gas
被细菌腐蚀，产生了天然气
that bubbles up from the floor of the lake.
泡泡从湖底冒出。
That gas is methane and we've been collecting it all night
这种气体是甲烷，我们晚上一直在收集
underneath this upturned boat
从这个倒过的小船
so that I can take a sample of it in this bag.
这样我可以收集到这个袋子。
Now, on Earth, methane is very unstable.
现在，地球上，甲烷很不稳定。
If you give it...
如果你给它...
a little kick...
一点外力...
in the presence of oxygen, then you get what chemists call an exothermic reaction.
有氧气存在，化学中的放热反应。
Methane plus oxygen goes to water plus carbon dioxide, and...
甲烷加氧，得到水和二氧化碳，并且...
some energy.
还有一些能源。
The Earth's temperature and atmospheric pressure
地球的温度和大气压力
means methane can only exist as a highly-flammable gas.
意味着甲烷只能作为一种高度易燃气体。
But Titan's atmospheric pressure and temperature
但土卫六的大气压力和温度是完美的，
is perfect to allow methane to exist as a solid, a gas and, most importantly,
能让甲烷作为固态，气态，
a liquid.
最重要的，是液态。
So the images Cassini captured were gigantic lakes of liquid methane...
因此，卡西尼号拍摄的图像，是巨大的液态甲烷湖泊...
..the first ever liquid discovered
..首次发现液体
pooling on the surface of another world in the solar system.
汇集在太阳系的另一个世界。
This is Kraken Mare.
这是Kraken Mare。
At over 400,000 square kilometres,
超过40万平方公里，
it's the biggest body of liquid on Titan.
土卫六上最大面积的液态湖。
It's almost five times the size of Lake Superior,
近5倍于苏必利尔湖的大小，
North America's greatest lake.
北美最大的湖泊。
On Titan, methane plays exactly the same role that water does here on Earth.
土卫六上，甲烷完全充当了地球上水的角色。
So, where we have clouds of water,
因此，我们有水蒸气的云，
Titan has clouds of methane with methane rain.
土卫六上有甲烷云和甲烷雨。
Whereas we have lakes and oceans of water, Titan has lakes of liquid methane.
我们有湖泊和海洋的水，土卫六有液态甲烷湖泊。
And whereas, here on Earth, the sun warms the water in the lakes and oceans,
在地球，太阳温暖了湖泊和海洋里的水，
and fills our atmosphere with water vapour,
我们的大气层充满着水蒸汽，
on Titan the sun lifts the methane
太阳让土卫六上的甲烷
from the lakes and saturates the atmosphere with methane.
从湖泊中蒸发，充满了大气层。
So, whereas on Earth we have a hydrological cycle, on Titan there's a methanological cycle.
因此，在地球我们有水循环，在土卫六有甲烷循环。
And rain would be an absolutely magical sight on Titan.
下雨将是土卫六上绝对神奇的景象。
Because the atmosphere is so dense and the gravity of the moon is so weak,
因为那里的大气是如此稠密，引力是如此薄弱，
the drops of methane rain would grow to over a centimetre in size
甲烷雨的雨滴大小超过1厘米
and they would fall to the ground as slowly as snowflakes fall onto the surface of our own planet.
它们落地的速度如雪花般缓慢。
Thousands and thousands of gallons of liquid methane
成千上万成千上万加仑的液态甲烷
must have slowly rained down onto the surface,
慢慢地落到地面，
making rivers and streams swell and burst.
河流和溪流得以扩展。
Deep gullies were cut into the frozen water landscape...
深沟渠被切断成冰冻的水景观...
Which looks so familiar because it is familiar.
情景太过熟悉了。
It's this. You know, the atmosphere of Titan shapes the surface in exactly the same way
土卫六的大气层以完全相同的方式塑造了地表
that the atmosphere here on Earth shapes the surface of our planet.
正如地球大气层塑造了我们这个星球的表面。
Titan is like a primordial Earth caught in a deep freeze.
土卫六就像是一颗原始的地球，陷入深冻状态。
It's almost like looking back in time over four billion years
这几乎是回头看，40亿年前
and observing our planet before life began, and began to modify our atmosphere,
我们的星球，在生命开始之前，开始改变我们的大气，
to change it into the oxygen-rich atmosphere that we see today.
改变到富氧，直至我们今天的大气层。
In many ways, Titan looks so familiar.
在许多方面，土卫六看起来很熟悉。
It's a place with rivers and lakes and clouds and rain.
这是一个有河流，有湖泊，有云层和降雨的地方。
It's a place with water, albeit frozen as hard as steel,
这是一个有水的地方，尽管冰冻后很硬，
and a place of methane, albeit so cold that methane is now a liquid
这是一个有甲烷的地方，虽然现在是作为液体存在
and flows and shapes the landscape just like water does here on Earth.
它塑造了这些景象，如同地球的水所做的。
For me, the most important thing about Titan
对我来说，土卫六最重要的是
is we now have two Earth-like worlds in our solar system
我们的太阳系，现在有两个类似地球的世界
One in this warm region, 93 million miles away from the sun,
一个是离太阳9300万英里远，温暖的地区，
and the other in deep freeze, a billion miles away from our star
一个是极寒，离我们的恒星十亿英里远
in orbit around another planet, and that must greatly increase the probability
它环绕着另一颗行星，其（出现生命的）概率
that there are other Earth-like planets in orbit
远远大于其他类地行星
around the hundreds of billions of stars out there in the universe.
在星系数千亿的恒星里。
# Somewhere over the rainbow
# Skies are blue
# And the dreams that you dare to dream
# Really do come true. #