行星（2019）

经过20年的不懈努力 金星13号♥探测器终于可以尝试危险的着陆了
After 20 years of trying, Venera 13 began its perilous descent.
它已经蓄势以待 准备承受
The craft was prepared to withstand pressures
短短几秒就能摧毁汽车的压力
that could crush a car in seconds...
和足以融化铅的炽热高温
..in temperatures that would melt lead.
1982年3月1日
On March 1st 1982...
苏联人拍到了金星表面的
..the Soviets took the first full colour picture...
第一张全彩照片
..of the Venusian surface.
尽管环境条件极其恶劣
Even under the most extreme of conditions,
这个探测器还是向地球传回了大量珍贵数据
the probe sent its precious data home to Earth...
温度 457摄氏度
大气层 二氧化碳含量96.5%
在成功着陆127分钟后 它最终解体
..until, 127 minutes after touchdown, it finally succumbed.
大气压 地球大气压的89倍
金星根本不是水光潋滟的海洋世界
Far from a benign ocean world...
相反更像是人间地狱
..Venus is a vision of hell...
生命在这里根本无法存活
..where no life can survive.
金星到底是哪里出问题了
So where did it all go wrong for Venus?
这个问题问得好 而且非常重要
Well, that is a good question and it's an important one.
有人说 我们只有充分了解金星
It's been said that we won't fully understand the Earth
才能真正地了解地球
until we understand Venus
因为这两颗行星实在太相似了
and that's because the planets are so similar.
据我们所知 金星的大小和构成
Venus is the same size as the Earth.
几乎和地球完全相同
It's the same composition, as far as we know.
它虽然距离太阳更近 但也不像水星那么近
And although it's closer to the sun, it's not as close as Mercury.
那么为何地球这边仍是天堂
So why is it that one world remained heaven
而另一个却变成了地狱呢
whilst the other became hell?
令人意想不到的是 金星的表面温度
Counterintuitively, the surface temperatures today on Venus
要远远高于水星
are hotter than those on Mercury...
金星的气候变化加复杂
..and the story of Venus's climate is further complicated
因为太阳本身的不断变化
by the fact that, over the lifetime of the planet,
影响了金星漫长的生命历程
the sun itself has been evolving.
随着太阳日益老化 这颗恒星的温度变得越来越高
As the sun gets older, the star burns hotter and hotter and hotter.
也就是说 在过去太阳还年轻的时候
That means that, in the past, when the sun was younger,
温度肯定要更低一些
it must have been cooler.
它被称为“黯淡太阳”
It's called the faint young sun
这对各大行星产生了重要影响
and that has a big impact on the planets.
在35亿年到40亿前 当地球上
At the time, when life was just about beginning on the Earth,
开始出现生命时
three-and-a-half to four billion years ago,
太阳的光芒还比较黯淡 这意味着金星上的温度要低得多
the sun was fainter and that means that Venus was cooler.
事实上当时金星的表面温度
In fact, temperatures on Venus at that time
就像地球上的宜人春天一样
would have been like a pleasant spring day here on Earth.
44亿年前
在金星形成大约几百万年之后
Within a few million years of its formation,
它的表面开始渐渐冷却
the surface of Venus had cooled.
当时的金星与黯淡太阳的距离刚刚合适
The planet now found itself at just the right distance
因此其表面出现了类似地球的
from the faint young sun for Venus to experience a sight
繁荣景象
familiar to us here on Earth.
天堂的大门打开
The heavens opened.
奔涌的水流浸没了金星的表面
Great torrents flooded the surface.
大小河流随处可见
Rivers of water flowed.
金星变成了一个海洋世界
Venus became an ocean world.
金星的大气层就像一张厚厚的毯子
The planet's atmosphere allowed it to hold on to the oceans...
确保地表温度恒定以及海洋的持续存在
..by acting as a blanket, keeping the surface temperate...
这要多亏了温室效应
..thanks to the greenhouse effect.
温室效应是个很简单的物理现象
The greenhouse effect is pretty simple physics.
行星大气层中类似二氧化碳和水蒸汽这样的气体
The gases like carbon dioxide, water vapour and the planetary atmosphere
在可见光下是透明的
are transparent to visible light
这显然是因为我们能看到
and it's obvious because there's a source of visible light,
存在一个可见光源 太阳
the sun, and I can see it.
太阳辐射光落在行星表面
So that radiation falls onto the surface of the planet
使其表面温度升高 随后岩石将光线
and it heats it up. The rocks then re-radiate that
重新辐射到大气中
out into the atmosphere again,
但这次的呈现形式并非是可见光 而是红外线
but, this time, not as visible light, but as infrared,
我的肉眼是看不到的
which my eyes can't see.
现在二氧化碳和水蒸气吸收红外线
Now, carbon dioxide and water vapour absorb infrared,
由此获得能量 促使行星表面升温
and so they trap that energy and the planet heats up.
这种现象不一定是坏事
Now, that's not necessarily a bad thing.
如果没有温室效应 地球的平均温度
The Earth would be at an average temperature
将保持在零下18摄氏度左右
of around minus 18 degrees Celsius without the greenhouse effect,
但是变暖和煎烤之间 往往只是一线之隔
but there is a thin line between heating the planet up and frying it.
渐渐地经过20多亿年的发展 年轻的太阳变得越发明亮
Gradually, over two billion years, the young sun grew brighter.
金星表面的温度开始升高 越来越多的水蒸汽
Temperatures began to rise, lifting more and more water vapour
进入大气层
into the atmosphere.
温室效应变得更加强烈
The greenhouse effect grew more intense.
雨水不等到达地面就已经蒸发殆尽
Rain evaporated long before reaching the ground.
金星已经到达临界点
Venus had reached a tipping point.
温室效应开始逐渐失控
A runaway greenhouse effect had taken hold.
金星沐浴在阳光下的日子成为过去
Venus's moment in the sun was over.
如今它皲裂的表面 甚至比水星表面的温度还高
Its cracked surface today is even hotter than Mercury's,
金星因此成为所有行星中温度最高的星球
making Venus the hottest of all the planets.
当年轻太阳的亮度持续增加时
As the young sun's brightness continued to increase,
所有类地行星都感受到了它的影响
the effects were felt across all the terrestrial planets.
火星 距离太阳2.28亿公里
火星比金星距离太阳更远 也能旱受到阳光的温暖
Mars, much further out than Venus, enjoyed its moment in the sun too.
35亿年前
火星的大气层中富含温室气体
With an atmosphere rich in greenhouse gases,
河流在火星表面流淌了数亿年
rivers flowed across its surface for hundreds of millions of years.
但是火星比金星的体积小 无法保持其大气层
But Mars, being smaller than Venus, couldn't hold on to its atmosphere.
火星上的水大都蒸发
Much of its water evaporated and...
并逃逸到了太空中
..and escaped into space...
少量水得以保存
..leaving only small traces behind,
冰封在火星的零星角落
frozen in patches across the planet...
人类在继续执行火星任务
..where missions continue to search
前去寻找地外生命的最初迹象
for the first signs of extraterrestrial life.
火星上有个名叫海腊斯盆地的火山口
There's a crater on Mars called the Hellas Basin,
直径1500公里 深9000米
which is 1,500 km across and 9km deep.
换句话说整个珠穆朗玛峰放进去后
That means you could put Everest on the floor
都无法到达火山口边缘
and the summit would not reach the rim.
火山下面的气压很高
The air pressure is so high down there
很可能存在液态水
that liquid water can exist.
所以我们可以想象 很可能有微生物
So I suppose it's not impossible to imagine microbes
从地下深处爬到火星表面 在正午的烈日下晒太阳
coming up from deep below the surface to bask in the midday sun
然后再重新消失在地下
before disappearing back down below again
熬过寒冷刺骨的夜晚
to survive the cold of the Martian night.
但是就算生命确实存在
But if life does exist out there,
也肯定只是些简单生命
it will certainly only be simple life.
其它任何行星都无法孕育出像你我这样的复杂生命
There will be nothing anywhere near as complex as you or me,
不会有地球这样的环境
or even this plant.
地球 距离太阳1.5亿公里
从某种意义上讲 太阳系的故事
The story of the solar system is, in a sense,
就是系内几大岩石行星
a story of instability and constant change,
动荡不安的变化史
at least for the inner rocky worlds.
水星已经彻底改变位置
Mercury has changed its position radically.
开始围绕更靠近太阳的轨道运行
Its orbit now takes it close to the searing heat of the sun.
金星表面或许曾经水波荡漾
Venus probably had water on its surface
可是大约20亿年后 它的表面温度甚至超过了水星
for around two billion years before it became hotter than Mercury.
火星在大约35亿年前
And Mars lost its oceans and rivers
失去了所有的河流与海洋
perhaps three-and-a-half billion years ago.
在所有行星中唯有地球显得与众不同
But unique amongst those worlds is Earth
因为它与40亿年前几乎毫无两样
because it's remained pretty much like this,
地表一直存在液态水
liquid water on the surface, for four billion years,
这为复杂有机化学的发展创造了条件
and that has allowed complex carbon chemistry to develop.
今天我们的地球生机勃勃
Today, our planet is dominated by life.
生命之花遍布全球各个角落 瞧瞧这地方
It's in every nook and cranny. I mean, look at this place.
这是位于大西洋中部的一座火山
This is a volcano in the middle of the Atlantic Ocean
到处是生机盎然的景象
and it is literally teeming with life.
想想看 大约40亿年前发生的
And think about all the chance events that had to happen
所有偶然事件
over four billion years
只是为了创造出这个礁池中的微小生命
just to produce the little creatures in this rock pool.
生命早已和地球构造紧密交织在一起
Life has woven itself into the fabric of the planet.
它是所有大♥陆♥和海洋的重要组成部分
It's an integral part of every continent and every ocean.
它对确保大气平衡
It plays a crucial role
维持地球的温和气候
in maintaining the balance of our atmosphere...
发挥着至关重要的作用