宇宙时空之旅（2014）

Cosmos: A SpaceTime Odyssey S01E02

Part 5 April 25, 2021, 12:39 p.m.

Noxious bacteria bloomed,
海洋里几乎所有其他生命都死去了
but nearly everything else in the seas died.
污浊的水域向空气中释放出致命的硫化氢气体
The stagnant waters belched deadly hydrogen sulfide gas into the air,
使大多数陆地动物窒息而死
which suffocated most of the land animals.
地球上百分之九十的物种都灭绝了
Nine in ten of all species on the planet went extinct.
我们称之为
We call it...
大灭绝
The Great Dying.
地球上的生物几乎被消灭殆尽
Life on Earth came so near to being wiped out
经历了一千万年才恢复过来
that it took more than ten million years to recover.
但新的生命形态在缓慢进化
But new life-forms slowly evolved
来填补二叠纪大灭绝留下的空白
to fill the openings left by the Permian holocaust.
这中间最大的赢家就是恐龙
Among the biggest winners were the dinosaurs.
现在地球是它们的了
Now the Earth was their planet.
它们的时代持续了1亿5千多万年
Their reign continued for over 150 million years.
直到在另一场大灭绝中被摧毁
Until it, too, came crashing down in another mass extinction.
地球上的生命在跨越万古的过程中历尽艰辛
Life on Earth has taken quite a beating over the eons.
并仍然存活下来
And yet it's still there.
生命坚韧得令人难以置信
The tenacity of life is mind-boggling.
我们总在意想不到的地方发现它
We keep finding it where no one thought it could be.
至于那道未命名的走廊
That nameless corridor?
是留给以后的
That's for another day.
我知道有一种动物可以生活在沸水中
I know an animal that can live in boiling water
或在坚冰中
or in solid ice.
可以十年不喝水
It can go ten years without a drop of water.
可以裸♥露♥在寒冷真空
It can travel naked in the cold vacuum
且充满强辐射的宇宙中
and intense radiation of space
并毫发无损地归来
and will return unscathed.
缓步类动物或称水熊虫
The tardigrade, or water bear.
无论在最高的山顶
It's equally at home atop the tallest mountains
还是在最深的海沟它都同样自在
and in the deepest trenches of the sea.
在我们的后院它们大量聚集
And in our own backyards, where they live among the moss
在苔藓间生活
in countless numbers.
大概你从未察觉过它们
You've probably never noticed them
因为它们太小了
because they're so small.
像针尖那么小
About the size of a pinpoint.
但它们很顽强
But they're tough.
缓步类动物躲过了五场大灭绝
The tardigrades have survived all five mass extinctions.
已存在五亿年之久
They've been in business for a half a billion years.
我们曾认为生命很挑剔
We used to think that life was finicky,
只能生根于
that it would only take hold where it was
不太热不太冷
not too hot, not too cold,
不太暗不咸不酸无辐射的地方
not too dark or salty or acidic or radioactive.
还有不管怎样都不能没有水
And whatever you do, don't forget to add water.
可是我们错了
We were wrong.
顽强的缓步类动物告诉我们
As the hardy tardigrade demonstrates,
生命可以忍♥耐
life can endure conditions
人类不能承受的恶劣环境
that would mean certain death for us humans.
但地球上极端环境里的生物
But differences between us and life found
和我们之间的区别
in even the most extreme environments on our planet
就像相同主旋律上的变奏
are only variations on a single theme,
同种语言中的不同方言
dialects of a single language.
即地球生物的遗传密♥码♥
The genetic code of Earth life.
其他星球上的生物是什么样的呢
But what would life be like on other worlds?
有着与地球截然不同的历史
Worlds with a completely different history,
化学成分和演化的星球
chemistry and evolution from our planet?
我想带你们去一个遥远的世界
There's a distant world I want to take you to--
一个与我们的世界大相径庭
a world far different from our own,
但可能孕育生命的世界
but one that may harbor life.
如果这是真的它的样子
If it does, it promises to be unlike anything
一定是我们见所未见的
we've ever seen before.
云雾遮盖土卫六的整个表面
Clouds and haze completely hide the surface of Titan,
它是土星的巨大卫星
Saturn's giant moon.
土卫六有种家的感觉
Titan reminds me a little bit of home.
像地球一样它的大气主要由氮气构成
Like Earth, it has an atmosphere that's mostly nitrogen.
却是地球大气密度的四倍
But it's four times denser.
土卫六的空气中没有氧气
Titan's air has no oxygen at all.
比地球上任何一个地方都寒冷
And it's far colder than anywhere on Earth.
尽管如此我还是想去
But still... I want to go there.
我们必须穿过
We have to descend
几百千米的烟雾
through a couple hundred kilometers of smog
才能看到它的表面
before we can even see the surface.
掩藏在下面的是熟悉到奇怪的地貌
But hidden beneath lies a weirdly familiar landscape.
在太阳系中只有地球和土卫六上
Titan is the only other world in the solar system
存在降雨
where it ever rains.
它拥有河流和海岸线
It has rivers and coastlines.
和数以百计的湖泊
Titan has hundreds of lakes.
其中一个比北美的苏必利尔湖更大
One of them larger than Lake Superior in North America.
湖水蒸发
Vapor rising from the lakes
冷凝后又变成雨水
condenses and falls again as rain.
雨水落入河流
The rain feeds rivers,
冲刷出山谷的地貌
which carve valleys into the landscape,
就像在地球上一样
just like on Earth.
但有一个重大的不同
But with one big difference.
在土卫六上所有的海洋和雨水
On Titan, the seas and the rain
不是水而是甲烷和乙烷
are made not of water but of methane and ethane.
在地球上这些分子组成天然气
On Earth, those molecules form natural gas.
而在寒冷的土卫六上
On frigid Titan,
它们以液态存在
they're liquid.
土卫六上有很多水
Titan has lots of water,
但全部结成坚冰
but all of it is frozen hard as rock.
事实上它的地形和山脉
In fact, the landscape and mountains
主要由水冰构成
are made mainly of water ice.
土卫六的温度为零下二百度左右
At hundreds of degrees below zero,
水不可能以液态存在
Titan is far too cold for water to ever be liquid.
卡尔·萨根之后的天体生物学家都想知道
Astrobiologists since Carl Sagan have wondered
土卫六充满碳氢化合物的湖泊中有无生命
if life might swim in Titan's hydrocarbon lakes.
这种生命的化学基础
The chemical basis for such life
一定会颠覆我们已有的认知
would have to be entirely different from anything we know.
地球上所有生命都依赖于液态水
All life on Earth depends on liquid water.
而土卫六的表面不满足这个条件
And Titan's surface has none of that.
但我们可以想象其他类型的生命
But we can imagine other kinds of life.
它们可能吸入氮气
There might be creatures that inhale hydrogen
而非氧气
instead of oxygen.
呼出甲烷而非二氧化碳
And exhale methane instead of carbon dioxide.
用乙炔代替糖类作为能量来源
They might use acetylene instead of sugar as an energy source.
我们如何得知在黑色波浪下
How could we find out if such creatures
是否有生命统治这个隐秘的帝国呢
rule a hidden empire beneath the oil-dark waves?
我们潜入克拉肯海的深处
We're diving down deep into the Kraken Sea,
它是以神话中的挪威♥海♥怪命名的
named for the mythic Norse sea monster.
即便里面真的有海怪
Even if there is one of those down there,
我们也八成看不到
we probably couldn't see it.
太暗了
It's so dark.
地球上所有石油和天然气加起来
If you took all the oil and natural gas on Earth,
也只是土卫六油气储备的一小部分
it would amount to but a tiny fraction of Titan's reserves.
让我们开几盏灯
Let's turn on some lights.
此刻我们处于两百米深
We're now 200 meters beneath the surface.
你看到什么东西了吗
Did you see something?
在那边喷发口旁边
Over there, by that vent.
可能是我自己想象的
Maybe it was just my imagination.
如果想确切查证
I guess we'll have to come back
我们得改日再来
if we want to find out for sure.
我还想再讲最后一个故事
There's one last story I want to tell you.
科学史上最伟大的故事
And it's the greatest story science has ever told.
这是关于地球上生命的故事
It's the story of life on our world.
欢迎来到四十亿年前的地球
Welcome to the Earth of four billion years ago.
这是生命诞生前的地球
This was our planet before life.
没人知道生命是如何诞生的
Nobody knows how life got started.
那个时代留下的线索
Most of the evidence from that time
大多已被撞击和侵蚀销毁
was destroyed by impact and erosion.
科学在知识与无知的边界探索
Science works on the frontier between knowledge and ignorance.
我们不怕承认自己不知道