行星（2019）

that makes Enceladus so special.
我们在土卫二的冰层下所取得的发现
What we found beneath Enceladus's shell of ice must rank
可以说是21世纪太空探索领域最伟大的发现之一
as one of the greatest discoveries in 21st-century space exploration.
但这也是一个很容易被人们忽略的现象
But it was a discovery that had been hiding in plain sight.
这是一张“旅行者”1号♥在1980年拍摄的土卫二的照片
This is a photograph taken by Voyager 1 of Enceladus in 1980.
当时没有人看出有什么特别之处
Now, nobody noticed anything remarkable about it at the time
现在这幅图像被增强处理过了 现在我们可以看到
but this image has been enhanced and now you can see
在卫星的这一侧有这种模糊的斑点
this sort of misty blob off one side of the moon.
这很有意思
Now, that is fascinating.
这说明有什么东西从土卫二的内部冲向了太空
It means something is rising up from inside Enceladus.
当“卡西尼”号♥探测器在24年后到达那里时 它也看到了同样的情形
Now, when Cassini got back there 24 years later it saw the same thing,
但这次的细节更为清晰了
but this time in much more detail.
当“卡西尼”号♥探测器接近土卫二时 人们立即发现了异常之处
As Cassini approached Enceladus, the anomaly revealed itself.
巨大的水蒸气和冰体从卫星的表面喷发出来
Giant plumes of water vapour and ice were erupting from its surface.
每秒喷发出的物质超过了200公斤
Over 200kg of material was being released every second.
但这些物质并没有散逸到太空中去
But this material was not lost to space.
却像是在填补土星的一个外环
It seemed to be feeding one of Saturn's outside rings,
使它更加完整
helping to replenish it.
这些发现让研究人员决定尝试一次大胆的冒险
And these discoveries inspired an audacious risk.
他们要在10亿多公里外
Piloted from over a billion kilometres away,
引导“卡西尼”号♥靠近那些危险的羽流
Cassini was guided dangerously close to the plumes.
探测器从距离土卫二表面不到48公里的上空
The craft passed within just 48km of the surface
掠过
of Enceladus.
“卡西尼”号♥真正接触到了那些羽流
And Cassini was able to touch the plumes.
经过探测器连续多次的飞越 我们取得了
What we discovered, thanks to a series of these flybys,
令人叹为观止的发现
was breathtaking.
羽流中的冰实际上是冻结的海水冰晶
The ice in the plumes was actually frozen particles of salty water.
我们发现了一个在向太空渗漏的地下海洋
We had found a subsurface ocean leaking into space.
土卫二距离太阳极为遥远
Far, far from the sun,
它的表面下藏匿着一个液态的海洋
Enceladus was harbouring an ocean of liquid water.
而这片海的存在也是由于土星的原因
And it was there because of Saturn.
土卫二以椭圆轨道绕土星运行
Enceladus orbits Saturn in an elliptical orbit,
这意味着土星对土卫二施加的引力大小
which means the gravitational forces across the moon
是不断变化的
are constantly changing.
土卫二之所以形成这样的轨道 是由于受到了另一颗较大的卫星
It's maintained in this orbit by the pull of another larger moon -
土卫四的引力作用
Dione.
持续变化的引力拉伸和挤压着土卫二的内部
These ever shifting gravitational forces stretch and squeeze
加热融化它的冰质内核
its heart, warming and melting its icy interior.
“卡西尼”号♥取得的发现数据还存在另一个惊喜
But Cassini's data had one more surprise in store.
我们在对水冰羽流进行更为详细的分♥析♥后
As the plumes of water ice were analysed in ever greater detail,
我们发现了
we discovered complex organic compounds
只会来自深海热泉喷口的
and silica particles that could only have come
复杂有机化合物和硅微粒
from hot hydrothermal vents.
在寒冷的太阳系外缘
In the frozen outer reaches of the Solar System
我们居然发现了一处温暖湿润的绿洲
we had found a warm watery oasis.
“卡西尼”号♥让我们看到了土卫二冰层下的景象
Cassini has given us a glimpse beneath the ice of Enceladus,
从科学意义上讲这是真正吸引人的地方
and it is fascinating genuinely in a scientific sense because many
因为许多生物学家相信像这样的热泉喷口
biologists believe that hydrothermal vents like those that are almost
几乎可以肯定存在于土卫二的海底
certainly present on the floor of Enceladus's ocean
热泉就是地球生命的摇篮
were the cradle of life on Earth.
所有的成分都齐备
All the ingredients are present -
有热水与冰和矿物质的接触
there's hot water in touch with ice and minerals.
这就是个巨大的化学反应炉
That's a reactive cauldron of chemistry.
有活性气体 甲烷
There are reactive gases - methane.
“卡西尼”号♥在羽流中发现了氢分子
Cassini found molecular hydrogen in the plumes,
这是地球上原始生命的食物来源之一
and that was one of the food sources of primitive organisms on Earth.
所以说现在土星外♥围♥的轨道上
So there really is a possibility that there is life
确实有存在生命的可能性
in orbit around Saturn today.
土卫二上存在生命的预期令人兴奋
The prospect of life on Enceladus is exciting.
但即便那里存在 也只可能是最简单
But if it's there, it's likely to be only the simplest
最原始的生物
and most primitive of organisms.
而且 由于土星曾经的动荡和善变
And given how violent and changeable Saturn's past has been,
这个由冰体和液态水构成的世界或许只是不久前
this world of ice and liquid water may only have arisen
才出现的
relatively recently.
我们不清楚土卫二
Now, we don't know how long
进入地质活跃期多长时间了 也不知道它的海洋存在了多久
Enceladus has been geologically active, how long its had an ocean.
如果说只有1000万年 哪怕是几亿年的话
If it was only tens of millions or even hundreds of millions of years,
那么这段时间还不足以发展出生命
that may not have been enough time for life to get going.
但是如果那里有生命存在 我们就可以预知未来了
But if there is life there then we can glimpse its future
因为如今地球上仍然存在深海热泉喷口
because there are still hydrothermal vent systems present on Earth today
那里的生命不仅生存了下来 而且十分兴旺
and life doesn't just survive there, it thrives.
热泉喷口通常位于深海下的地壳断裂带中
Often found in the deep oceans along fault lines in the Earth's crust,
那里是地球上最丰富 最复杂的
hydrothermal vents are some of the richest and most complex
生态系统之一
ecosystems on Earth.
这样的栖息地供养了
Feeding off the abundant bacteria that breed there,
众多奇异而复杂的生物 它们以大量繁殖的细菌为食
these habitats support a multitude of strange and complex organisms.
尽管这样的生物永远不会出现在土卫二上
Whilst creatures like this will never exist on Enceladus,
但几十亿年后 那个遥远的世界
billions of years from now, it is just possible that this
也许会形成自己独特的生命家园
distant world may become home to its own unique forms of life.
不过对“卡西尼”号♥探测器来说 土卫二冰层下的新奇世界
But for Cassini, the brave new world under the ice of Enceladus
却是一个令人喜忧参半的发现
was a bittersweet discovery.
2017年9月15日
绕土星飞行13年后
13 years after it arrived at Saturn,
“卡西尼”号♥的燃料终将耗尽
Cassini's fuel finally began to run dry.
美国国家航♥空♥航♥天♥局不敢冒险让这台探测器坠毁在土卫二上
NASA couldn't risk letting this probe crash land on Enceladus
避免污染一片潜在的生命温床
and contaminate a potential habitat for life.
这里是1号♥飞行控制台
Systems, ACS One.
我们刚切换到高速模式
We've just had transition to high rate mode.
喷射推进实验室控制中心
于是他们决定让“卡西尼”号♥进行最后一段飞行
And so the decision was made to send Cassini on one final journey.
它会飞向
A journey that would take it
土星的大气层内
into the atmosphere of Saturn itself.
那里将会是它的使命终结之地
A journey from which it would never return.
我们进入大气层了
And we are in the atmosphere.
无线电♥信♥♥号♥♥
Radio signal still holding.
存在30秒
30 seconds.
我们刚刚得知45秒后
Just heard the signal from the spacecraft is gone
探测器发出的信♥号♥♥会消失 探测器也将坠毁
and that, within the next 45 seconds, so will be the spacecraft.
土星见证了太阳系历史上的
The planet that had borne witness to some of the greatest dramas
一些最壮观的场面 现在却在吞噬
in the history of the Solar System was now consuming the craft
讲述它非凡故事的探测器
that had told its extraordinary story.
“卡西尼”号♥探测器和土星最终融为一体
Cassini and Saturn had now become inseparable companions.
经过长途飞行我们前往土星 去体验和探索
We journeyed out to Saturn to experience and explore
这至美的景色
this great beauty.
但最终 我们会在地球上提升对宇宙的认知
But in the end we were rewarded with insights closer to home.
“卡西尼”号♥测器和它的科研团队
Cassini and her team of scientists and engineers
称得上是最伟大的探险家之一
should be counted amongst our greatest of explorers.
这项任务具备探险的所有要素
The mission had all the ingredients -
一艘飞船和它的船员 穿越未知的海洋
a vessel and a crew drawn by the prospects of beauty
前往陌生世界 探索和了解美丽的新事物
and new knowledge across an uncharted ocean to an alien world.
正如探索中经常遇到的情形一样
And, as is so often the case in exploration,
真正的宝藏总是隐藏在出人意料的地方
the real treasure was found in the unexpected shadows.
这一次是在土星环的阴影之中
In this case, in the shadow of the rings,
我们发现了土卫二的小小世界
where we found this tiny world, Enceladus,
它或许能孕育生命 这让我们更加确信
that may harbour life and provide us with reassurance
人类在宇宙中并不孤单
that we are not alone in the universe.
看 这就是我们的发现之美
See? The beauty is in the story.
如果我们真在土卫二上发现了生命 会有意义吗
Would it matter really if we found life on Enceladus?
毕竟只是些微生物
It would only be microbes after all.
是的 而且很重要
Yes, it would matter.
我认为我们正处在历史上的一个阶段 我们需要一种自我认可
We are at a time in our history, I think, where we need reassurance
或者说是提醒 在我们的世界之外还存在着美和知识
or perhaps a reminder that there is beauty and knowledge
甚至是生命和意义 这很重要
and perhaps even life and meaning beyond our shores.
我确信 我们还会再次前往土星和它的卫星
We will, I'm sure, go back to Saturn and its moons,
做更深入的探索 停留更长时间
explore deeper, stay longer,
或许有一天我们甚至会亲自拜访
and maybe one day even visit ourselves.
我们不知道会发现什么
We don't know what we'll discover
但有一点是可以肯定的 这个故事才刚刚开始
but we can be sure that the story has only just begun.
《行星》幕后故事
“卡西尼”号♥是有史以来最成功的探测器之一
Cassini has been one of the most successful probes ever flown.
但是建造一台能够在太阳系外层空间
But constructing a machine that could survive 13 years
飞行13年的探测器 对每个参与其中的人来说都是极大的考验
in the outer Solar System was a huge challenge for everyone involved.