静谧的夜空中繁星闪烁 The night sky is ablaze with stars...
单纯我们银河系里的恒星就有数千亿颗 ..hundreds of billions in our galaxy alone...
其中有些比太阳更大 更亮 也更辉煌 ..many larger, brighter and more majestic than our sun.
从银河系和恒星的角度说 太阳系中的行星 On the scale of galaxies and stars, the planets of our solar system
不过是阳光偶然掠过的 are little more than grains of sand caught momentarily
一颗沙粒 in the light of the sun.
但是40多亿年来 这些微尘之上却写就了 But on those motes of dust, for over four billion years,
许多鲜为人知的壮丽史篇 great stories have played out unseen.
这是关于行星的诞生 Stories of worlds born...
还有消亡的故事 ..and worlds lost.
行星在沉寂平静中孕育 Planets forged amongst the calm...
在混沌中成形 ..and the chaos.
它们的命运纠缠关联 超乎我们的想象 Their destinies more entwined than we ever imagined.
我们知道这些 We know this...
是因为在过去的数十年间 ..because in the last few decades...
我们向太阳系中地球以外的其它7大行星 ..we've sent spacecraft to all seven...
都发射过探测器 ..of the worlds beyond our own.
我们这里要讲述的就是它们发送回地球的故事 These are the stories that they return to Earth,
也就是行星的故事 the stories of the planets.
行 星
46亿年前
在太阳诞生后的最初数百万年里 For the first few million years after the sun formed,
它的周围还没有行星出现 there were no planets to see it rise...
只有无尽的尘埃和气体 ..just clouds of dust and the gas...
这些是太阳诞生时残留的材料 ..the leftovers from the birth of the sun.
经过上千万年的时间 这些尘埃开始慢慢结合聚集 Over tens of millions of years, the dust began to stick together...
形成了最早的岩石 ..and form the first rocks.
最终这些岩石在引力作用下 Eventually, gravity assembled the rocks
创造出了行星的胚胎 to create planetary embryos...
随后催生出了距离太阳最近的4颗行星 ..that in time formed the four closest planets to the sun.
如今水星成为离太阳最近的行星 Today, Mercury is the closest of all,
承受着强烈的太阳光照 enduring the sun's full glare.
从水星继续向外 Further out...
是金星 ..lies Venus...
它的表面包裹着浓密的大气层 ..chocked by a thick atmosphere.
金星向外的邻居就是我们的地球 Then Venus's neighbour, Earth.
4颗行星中距离太阳最远的是火星 And farthest of all, Mars...
一个寒冷荒凉的世界 ..a cold desert world.
它们共同构成了太阳系中仅有的岩石行星 Together, they formed the only rocky so-called terrestrial planets
即“类地行星” in the solar system.
在这4颗行星中 And of the four...
有一颗显得独一无二 ..one is unique.
大家只要放眼四周 Just look at this...
聆听一番 ..and listen to it.
一颗行星在经历了 This is what a planet looks and sounds like
40亿年的自然进化后 便有了现在的音容外貌 after four billion years of evolution by natural selection.
太阳系中再也找不到 There is nowhere else in the solar system
与之相似的行星了 that looks and sounds like this,
这一点思索起来很有意思 which is interesting, when you think about it,
因为所有的行星和卫星都是由相同物质构成的 because all the planets and moons and are made out of the same stuff -
包括碳 氮 氧 铁 they're carbon, nitrogen, oxygen, iron.
45亿年前坍缩形成太阳系的尘埃云里 All those atoms were present in the cloud that collapsed
就包含所有这些原子 to form the solar system, four-and-a-half billion years ago.
然而地球却显得格外独特 And yet Earth appears to be exceptional -
它是荒芜太阳系中唯一一颗有生命的行星 a lone living planet in an otherwise desolate solar system.
到底是什么原因让地球显得如此特别呢 So what is it that makes this place so special?
是命中注定 还是巧合 Is it fate? Is it chance?
这些问题非常重要 These are important questions
因为地球是目前我们人类已知的 because Earth is the only place we know of
宇宙中存在的最复杂的现象 where the most complex phenomena in the universe exists,
它赋予了宇宙的意义 那就是生命 the thing that brings meaning to the universe - life.
第一集 沐浴阳光 类地行星
地球是太阳系中一个特别的世界 Earth is a special world in our solar system
甚至在数千光年的范围内也是如此 and perhaps even for thousands of light years beyond.
我们的世界确实有其独特之处 Our world certainly has unique properties.
地球的大小适当 与太阳的距离恰到好处 It's the right size and distance from the sun
这使它在数十亿年里能够保持大气层 to have retained an atmosphere that's protected its oceans
进而保护了地球上赋予生命的海洋 of life-giving water for billions of years.
可当我们离开这颗蓝色星球 But as we've left the blue planet,
去探索其它姊妹行星时 and explored our sister worlds...
我们发现每颗类地行星似乎都有过 ..we've discovered that each appears to have had a moment
酷似地球的环境 when it enjoyed almost Earth-like conditions.
每颗类地行星都曾有过生命诞生的机会 Every one of our rocky neighbours has a story of what might have been.
水星 距离太阳5800万公里
水星是一颗备受摧残的小个行星 Mercury is a small, tortured world.
数十亿年的光阴中 More than any other planet,
它始终承受着比其它所有行星更加狂暴的太阳炙烤 it's endured the unflinching glare of the sun for billions of years.
水星是个充满谜团与矛盾的世界 Mercury is a world of mystery and apparent contradictions.
它的运行轨道呈椭圆形 It's in quite an elliptical orbit,
这意味着它在远日点 离太阳是7000万公里 which means it can be as far away from the sun as 70 million km,
近日点却只有4600万公里 but as close as 46 million.
所以正午时 That means that temperatures at midday
水星的地表温度高达430摄氏度 can rise to 430 degrees Celsius on the surface,
到了夜晚因为它很小 本身没有大气层 but, at night, because it's a small planet and it's got no atmosphere,
温度会骤降至零下170摄氏度 temperatures fall to minus 170 degrees.
它也受到了所谓“轨旋共振”的困扰 It's also locked into what's called the spin-orbit resonance,
换句话说 水星每公转两周 which means the planet spins precisely three times on its axis
就可以完成自转三周 for every two orbits
这意味着水星上的一天几乎相当于两个水星年 and that in turn means that its day is twice as long as its year.
也就是说 我以每小时3.2公里的速度 That means that I could walk over the surface like this
在水星表面行走 about 2mph
太阳在空中的位置将始终不变 and keep the sun at the same point in the sky.
我能在水恒的暮色中一直走下去 I could stroll in eternal twilight.
水星是迄今为止人类探索最少的太阳系内层类地行星 Mercury is the least explored of the inner rocky worlds...
因为水星的公转轨道呈奇特的椭圆形 ..because getting to a planet in such a strange oval-shaped orbit,
距离太阳太近 so close to the sun...
人类探测水星存在巨大挑战 ..is a tremendous challenge.
5 4 3 Five, four, three,
引擎点火 2 1 0 main engine start, two, one and zero.
美国国家航空航天局的“信使”号探测器升空 And lift off of Messenger on Nasa's mission to Mercury...
“信使”号水星探测器 2004年8月
它是太阳系中一颗充满迷雾的行星 ..a planetary enigma in our inner solar system.
现在 探测器穿越音障 Now going through the sound barrier.
直接飞向水星明显不切实际 A direct route to Mercury is impractical.
现在要进入最大动压阶段 Now going through the period of maximum dynamic pressure.
探测器抵达目的地时的速度可能太大 A spacecraft would arrive with so much speed
需要大量燃料用于减速 that it would need vast amounts of fuel to slow down
并进入绕水星轨道 and enter orbit around Mercury.
火箭分离成功 We just had spacecraft separation.
“信使”号探测器 So Messenger controlled its trajectory
以各行星作为跳板 控制飞行轨道 by stepping from one planet to the next,
同时借助引力降低速度 using gravity to slow itself,
呈螺旋形靠近目标 spiralling inwards towards its target.
一次飞掠地球
两次飞掠金星
即便如此 “信使”号接近水星的速度依旧很高 Even so, Messenger approached Mercury at such high speed
不得不三次飞过水星 that it was forced to fly past the planet three times...
通过每次掠过实现减速 ..slowing on each pass...
经过将近7年准确无误的飞行后 ..until, after almost seven years of flawless navigation,
“信使”号终于安全进入绕水星轨道 it arrived safely in orbit.
“信使”号探测器的使命是探测水星表面 Messenger set about its mission to map Mercury's surface...
同时它将以前所未有的特写镜头 揭开这颗太阳系中 ..and began revealing the secrets of the most cratered planet
陨石坑最密集行星的秘密 in the solar system in exquisite new detail.
柯特兹撞击坑 直径33公里
凝固的岩浆流
卡洛里盆地 最大的撞击坑 1550公里
“信使”号探测器能做的 Messenger was able to do much more
不只是拍摄水星表的照片而已 than just take images of Mercury's surface.
通过追踪探测器发射的无线电信号 By tracking radio signals emitted by the spacecraft,
我们能够从地球上看到绕水星轨道的 we're able to see very slight changes in the orbital path
所有细微变化 around Mercury, as seen from Earth,
由此绘制出水星的引力场 and that allows us to map out Mercury's gravitational field.
探测器上的仪器 There are also instruments that allow us
还能让我们看到水星自转时的 to see how the planet wobbles around
晃动情况 as it spins on its axis.
我们把所有测量数据集中起来 And putting all these measurements together
就能得到水星的横截面 allows us to take a cross section through the planet,
进而判断出它的构成 to see what it's made of.
结果我们取得了某种奇怪的发现 And when we do that, we find something very strange.
水星的内核占据了 Mercury's core extends out about 85%
从其核心到地表大约85％的范围 from the centre of the planet to the surface.
这几乎就是一颗完全暴露的行星核心 It's almost entirely an exposed planetary core.
就好像水星表面的岩石外衣 It's as if the rocks of the surface were smashed away
在过去被粉碎剥离了一样 and removed at some point in its past.
探测结果还不止于此 And there was more.
“信使”号在这颗距离太阳最近的水星上 The tiny probe began detecting chemical elements in concentrations
还探测到许多化学元素的浓度简直出人意料 that no-one had thought possible this close to the sun.
硫 1.4%
钾 0.03-0.24%
水星表面居然有含量较高的 The discovery of relatively large concentrations of elements
硫和钾这类元素 like sulphur and potassium on Mercury's surface
这项发现确实让人大吃一惊 was a huge surprise.
要知道在行星形成之时 If you think back to the time when the planets were forming,
水星在如此靠近太阳的公转轨道上 不太可能出现 you don't expect high concentrations of those elements close to the sun,
如此高含量的化学元素 因为它们是挥发性元素 where Mercury orbits today, because they're so-called volatile elements.
很容易蒸发 They boil away easily,
通常只有在距太阳较远的寒冷区域 so you only find high concentrations further out,
才会达到如此高的含量 in the colder reaches of the solar system.
所以水星确实是个谜 So Mercury is an enigma
类似这些发现 促使我们不得不重新思考 and discoveries like these have forced us to completely rethink
有关行星形成的理论 our theories about the formation of the planet.
水星 45亿年前
在形成后的数百万年里 Just a few million years after its formation,
水星仍旧在肆意喷吐剧烈诞生时的热量 Mercury was still seething with the heat of its violent birth.
之后它渐渐冷却 地壳形成 Slowly, it cooled and a crust formed.
随着时间推移 地壳中吸收了 Over time, the crust became enriched
从水星内核逃逸出的挥发性元素 in the volatile elements that were escaping Mercury's interior.
但发生这种情况的唯一可能是 But this could only happen if Mercury started out
水星诞生之时处于更加远离太阳的地方 not in the position we see it today...
而不会是现在的位置 ..but much further out.
我们现在认为水星诞生于离太阳1.7亿公里的地方 We now think Mercury was born perhaps 170 million km
位置靠近火星的公转轨道 further away, close to the orbit of Mars...
如果它还待在原地的话 ..a place where, if it had stayed,
水星的命运或许会截然不同 its destiny could have been very different.
但事实并非如此 But it wasn't to be.
稚嫩的水星胚胎早在成熟之前就在引力作用下 The young planetary embryo was ripped from its promising position
产生了偏离 long before it could mature.
我们很难想象 Today, it's hard to imagine the planets
夜空中的行星所在的轨道会发生变化 in orbits other than the ones we see in the night sky.
它们似乎是永恒不变的存在 They feel eternal, permanent.
我们往往会把太阳系看作是 It's natural to think of the solar system
瑞士手表一样精密的天体表盘 as a piece of celestial clockwork, almost like a Swiss watch.
如果我们已知所有行星在某个时间点的位置 So if we knew where all the planets were at some point in time,
比如今天 我们就能计算出 let's say today, then we could imagine calculating
它们任何时间的确切位置 exactly where they're going to be at any point in time.
如果只是一颗行星和一颗恒星 这是没问题的 Now, that is true if there's only one planet and one star.
想象一下 那是太阳 这是水星 So imagine that's the sun and this is Mercury.
我们知道太阳和水星间的引力 Now, we know the gravitational force between Mercury and the sun.
如果只是这样 And, indeed, if that's all there is,
我们就能以最大的精确度 then we can calculate its orbit around the sun
计算出它围绕太阳运行的轨道 with essentially infinite precision.
可是如果再加一颗行星 比如说那边是木星 But add in one more planet, let's say Jupiter over there.
很显然这三个天体间都存在引力 Now there's a gravitational force between all three of these objects
那么原则上说 and it turns out that, even in principle,
我们根本不可能准确计算出 it is not possible to calculate exactly
它们将来的位置 where they're all going to be in the future
或者过去某个时间点的具体位置 or where they were at some point in the past.
这意味着以我们对行星位置的了解 This means that any uncertainty, even of a few metres
任何不确定性 哪怕只是几米之差 in our knowledge of the position of the planets,
都可能产生截然不同的预测结果 can lead to radically different predictions.
这是因为太阳系本身 包括行星的公转轨道 And that's because the system itself, the orbits of the planets,
在漫长的宇宙时间里是不稳定的 are not stable over very long timescales.
所以行星未必会始终保持在同一轨道上 So planets don't necessarily remain in the same orbits forever.
水星表面探测到的 And the evidence we've gathered
大量挥发性元素 from the volatiles on Mercury's surface,
以及超乎寻常的内核大小 and the unusual size of its core,
这些可能都在讲述着水星所经历过的故事 suggests that this may have been what happened.
45亿年前
如果水星真是在 If Mercury began its life
距离太阳1.7亿公里的地方孕育的 170 million km further away from the sun...
那它所在的空间区域 ..then it would have been in a region of space
很可能也是年轻火星的形成地 where the young Mars was also forming.
在这片空间区域内数十颗行星胚胎 This region was full of scores of planetary embryos,
你推我搡 争夺最佳位置 all fighting for position.
在一片混乱中 某个大型天体将水星推向了 Amongst the chaos, something large kicked Mercury inwards
太阳的怀抱 towards the sun.
水星与另一颗行星胚胎发生碰撞 Mercury collided with another embryo.
伴随着斜掠而过的撞击 水星的大部分地壳和地幔 A glancing blow saw much of its crust
散落进了茫茫太空 and mantle lost to space.
这些物质大都保留下来 Much of this material remained behind,
最终催生了早期的金星 perhaps helping to form the early Venus.
如果这一理论正确 那现在的水星 If this theory is correct, then Mercury,
不过是当初的内核 它继续向着太阳运动 now little more than a planetary core, continued towards the sun
最终形成了现在这种奇特的椭圆形轨道 and ended up in the peculiar elliptical orbit we see today.
水星在数十亿年前的剧烈撞击中 The idea that Mercury's outer layers were stripped away
被剥离外层的理论 从表面看来 in some violent collision many billions of years ago
的确很有吸引力 is a superficially attractive one,
这个理论也存在几个问题 but the theory does have problems.
如果撞击足够力道 都会造成水星升温 Any collision violent enough to do that heats up the planet
和挥发性元素逃逸 and that boils away the volatiles.
所以我们必须设想一种特别的碰撞 So you have to think of a very specific kind of collision,
或者可能是十分精妙的多次撞击 or perhaps even multiple more delicate collisions,
以与目前的数据吻合 in order to fit the data.
所以我觉得可以说 So I think it's fair to say that the precise nature
水星的具体形成原因仍旧是迄今为止行星科学中 of Mercury's formation is still one of the great unsolved mysteries
最大的未解之谜之一 in planetary science.
经过4年的观察 After four years of observation,
在发现水星动荡历史的线索后 and its discoveries that hint at Mercury's turbulent past,
“信使”号探测器的燃料终于完全耗尽 Messenger finally ran out of fuel...
它最终为这颗行星新增添了一个“陨石”坑 ..and added yet another crater to this tiny world
它或许会有截然不同的故事 that just perhaps could've had a different story to tell.
金星 距离太阳1.08亿公里
在水星外侧大约5000万公里的地方 50 million km beyond Mercury,
一颗终日包裹在云层下的行星 shrouded by an unbroken blanket of cloud...
乍看之下 ..lies a world which, at first sight,
它有更像地球的潜质 has the potential to be far more Earth-like.
看到夜空中那颗明亮的星星了吗 See that bright point of light out there in the evening sky?
那就是金星 That's Venus.
它的亮度很高 因为它是一颗巨大的行星 It's so bright because it's quite a large planet,
大小和地球相当 离太阳也不太远 about the same size as the Earth. It's not too far away.
特别是 But, in particular,
笼罩着高反射率的云层 because it's shrouded in highly reflective clouds.
这是金星令人难解 却又惹人遐想的一面 That's the frustrating but also tantalising thing about Venus.
即便在大型望远镜下 它依旧很低调 Even through a big telescope, when you look at it,
因为你永远看不到它的表面 it is featureless. You never see the surface.
直到20世纪50年代 And that meant that, even until the 1950s,
天文学家仍在猜测金星上存在生命 astronomers speculated that it might be a living world,
还有丛林 森林 河流和海洋 with jungles and forests and rivers and oceans.
以至于我们第一次向金星发射探测器时 So much so, in fact, that when we first sent a spacecraft to land
甚至做好了水上着陆的准备 on the surface of Venus, we prepared for a splash landing.
到达金星
塔斯社为您报道
苏联向金星
发射一枚宇宙探测器
金星号探测器
二十世纪六七十年代 Throughout the 1960s and '70s,
苏联的金星计划曾多次发射探测器探索金星 the Soviet's Venera programme sent multiple missions to explore Venus.
许多探测任务宣告失败 Many failed...
但每次尝试都让我们对金星表面 ..but, with each attempt, we learned a little more
极端恶劣的条件有了进一步了解 of the extreme conditions on the planet.
金星13号探测器 1982年3月1日
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 ..that keeps our planet temperate.
在所有类地行星中 Of all the terrestrial planets,
地球安然享受阳光的时间是最长的 Earth has enjoyed the longest moment of them all...
但这不会始终持续下去 ..but it can't last.
地球的命运终将跟随其它岩石行星的脚步 Earth will ultimately follow the fate of the other rocky planets
即使我们察觉不到每天的细微变化 because, even though we don't feel it day-to-day,
但太阳的老化过程不可逆转 the sun's ageing process is relentless.
我们可以肯定地说 太阳走向暮年之时 We can say with confidence what's going to happen to the sun
将会经历怎样的变化 towards the end of its life,
部分原因是我们懂得 partly because we understand physics
恒星内核所发生的物理和核物理变化 and the nuclear physics of what happens inside the cores of stars,
同时我们从夜空中也能解读出 but also because the life cycle of stars
恒星的生命周期 is written across the night sky.
我们以那颗明亮的星星为例 Take that bright star there, for example.
它叫大角星 It's called Arcturus.
它的质量与太阳相当 或许稍重一些 It's around the mass of the sun, perhaps a little bit heavier,
但它的年龄在60到80亿年之间 but it's between six and eight billion years old,
基本比太阳还要早诞生30亿年 perhaps three billion years older than the sun -
现在它成了一颗红巨星 and it is now a red giant star.
它内核的氢燃料已经耗尽 It's exhausted the hydrogen fuelled in its core,
开始膨胀冷却 and it's swollen up and cooled.
我们认为大约50亿年之后 And that is what we think will happen to the sun
这样的命运也会降临在太阳身上 in about five billion years' time.
当太阳核心的氢燃料彻底耗尽时 As the sun exhausts its hydrogen fuel in the core,
它的外部边界将会膨胀 its outer edge will inflate.
它将进入红巨星阶段 It will enter a red giant phase,
太阳将会向外扩张大约数百万公里 expanding millions of kilometres out into space.
水星首当其冲地遭到吞噬 Mercury will be the first to be engulfed.
然后 金星也将走向生命的终结 Then Venus's fate will be sealed.
地球或许能够勉强逃过前两位行星邻居的惨烈命运 Earth may just escape the fiery fate of its neighbours...
在太阳这颗濒死恒星的边缘 地球和火星挣扎求生 ..hanging on with Mars beyond the edge of the dying star.
四颗类地行星的时代即将结束 The era of the four terrestrial planets will be over.
昔日在其中一颗类地行星表面的繁荣生命 The lives lived on the surface of one of them
届时早已随风而逝 nothing more than a distant memory.
但这并不是故事的结尾 But that's not quite the end of the story.
就在太阳走向终结时 某些奇妙的事情将会发生 Right at the end of the sun's life, something wonderful will happen.
在整个太阳系历史上始终蓄势而发的 A collection of icy worlds that have lain dormant
一系列冰封世界即将从沉睡中醒来 for the entire history of the solar system will awake.
它们在围绕太阳系外层行星运行 These are the worlds that orbit the outer planets,
也就是木星和土星的卫星 the moons of Jupiter and Saturn.
这些围绕太阳系外层气态巨行星运行的遥远世界 These distant worlds that circle the outer gas giants
将日益变暖 will begin to warm...
比方说土星的土卫二 ..like Saturn's moon Enceladus...
或者木星的木卫二 ..or Jupiter's moon Europa.
在所有这些卫星中 我们认为有一颗卫星尤其重要 Amongst all these moons, there is one above all others
也存在极大的可能 that we think perhaps has the best chance
成为一个我们所熟识的世界 of becoming a place that we'd recognise.
它位于太阳系中遥远而又寒冷的地带 Way out in the cold, distant reaches of the solar system...
经过木星 ..past Jupiter...
围绕冰封的环状行星 ..around the icy-ringed planet Saturn,
土星运动 orbits a gem...
“卡西尼”号探测器正在飞往土星 And the Cassini spacecraft is on its way to Saturn.
它就是“泰坦” 土卫六 ..Titan...
土卫六的大小与行星相当 直径比水星还大 ..a planet-sized moon bigger than Mercury...
它被由氨气和甲烷组成的浓密大气包围 ..surrounded by a thick atmosphere of nitrogen and methane...
表面长期以来始终笼罩在迷雾之中 ..with a surface that has long remained a mystery.
“惠更斯”号探测器 2005年1月14日
“惠更斯”号探测器首次探索云层之下的 The Huygens probe was our first chance to explore
土卫六表面 beneath the clouds...
探测器上的照相机首次发回了对这颗遥远卫星的惊鸿一瞥 ..and its camera sent back these first glimpses of the distant moon.
令人惊奇的是 探测器实现了软着陆 Wonderfully, the craft made a soft landing
能够继续传输它所看到的画面 and continued to beam back what it saw.
这是一张非凡的照片 就像所有科学研究一样 This is a remarkable photograph and, as is always the case in science,
你了解得越多 就越发感觉神奇 the more you know about it, the more wonderful it gets.
这是一张从10亿公里外 This is a photograph from the surface of the moon
围绕土星运转的卫星表面拍摄的照片 orbiting around a planet over a billion kilometres away,
探测器上的照相机拍到了太阳系 so we've got a camera down onto the surface of a world
这个遥远冰冻地带的卫星表面 in the frozen far reaches of the solar system.
我们可以看到 它看着很像洪泛平原 What you see here is something that looks like a flood plain,
或者河床 就像我身边的这个 or a riverbed, very much like this, actually.
我们可以说这是河床或洪泛平原 And we can say that this is a riverbed or a flood plain
因为这颗卫星表面的岩石 because these rocks on the surface...
和这个很像 ..look like this.
它们都经受过流水的侵蚀和打磨 They've been smoothed and eroded by flowing liquid.
事实上 我们知道这些是水冰巨石 We know these are in fact boulders of frozen water.
它们冻得很结实 因为土卫六表面的温度 They're frozen solid because the temperature on the surface
低至零下180摄氏度 of this moon is minus 180 degrees Celsius.
这提出了一个有趣问题 That raises an interesting question.
在这么低的温度下 If it's so cold...
那些流动的液体会是什么呢 ..then what was the flowing liquid?
“惠更斯”探测器发现卫星表面有大量甲烷 Huygens detected significant amounts of methane...
这是地球上的一种可燃气体 ..a flammable gas on Earth.
土卫六表面气压相对较高 But the relatively high atmospheric pressure
加上温度极低 and cold temperatures at the surface of Titan
这意味着甲烷会以液体形式存在 means that this methane exists as a liquid.
“泰坦”表面可能很湿润 Titan could be wet...
但这不是水 而是液态甲烷 ..not with water, but with liquid methane...
在推动岩石一样的冰块沿着山间溪谷流下 ..driving rock-like chunks of ice down mountain channels
进入开阔的洪泛平原 and out into open flood plains.
“惠更斯”探测器只坚持了几小时 Huygens survived for just a few hours,
它在着陆点附近 but didn't detect any trace
没有发现任何液态甲烷的痕迹 of liquid methane at its landing site.
“卡西尼”号探测器 2006年
但是探测器的母船“卡西尼”号仍处于环土星轨道 But the probe's mother ship Cassini remained in orbit around Saturn.
在“惠更斯”登陆一年后 A year after Huygens landed,
“卡西尼”号再次掠过土卫六的北极 Cassini again flew high above Titan's North Pole
结果在太阳系地球以外的地方发现了 and discovered something seen nowhere else in the solar system
前所未见的东西 beyond Earth.
液体正在汇入不只一座 而是数十座巨大的湖泊 Liquid pooling into not just one, but scores of great lakes.
安大略拉库斯湖
丽姬亚海
克拉肯海
“卡西尼”号探测器发现了 Cassini discovered lakes...
液态甲烷湖 ..of liquid methane.
地球有了一个冰冷奇特的孪生姐妹 Earth has a strange cold twin.
从某些方面说 你可以想象船只漂浮在湖上的情景 In some ways, you could just imagine floating in a boat on those lakes
看起来就像我现在这样 and it'll look something like this,
只不过湖里的是液态甲烷 except this would be liquid methane gas
而那些山则由坚如磐石的 and those mountains there would be mountains of frozen water ice
水冰构成 as hard as rock.
此外令人着谜和好奇的是 What's also fascinating, and in fact tantalising,
土卫六上具有复杂的化学构成 is that Titan has a complex chemistry
是能够构成生命的有机化学成分 and that chemistry is carbon chemistry - the chemistry of life.
我们发现了类似氰化氢分子 So we found molecules like hydrogen cyanide,
这是氨基酸的组成部分 which are the building blocks of amino acids.
还发现了乙烯基氰七物这种分子 We found molecules called vinyl cyanides,
化学家和生物学家推测 which chemists and biologists speculate
它们或许能形成某种细胞膜 could form some sort of cell membranes.
所以土卫六存在构成生命的所有元素 And so all the ingredients for life are present on Titan.
现在几乎没有科学家认为泰坦卫星上存在生命 Now, very few scientists think there will be life on Titan today.
毕竟 它的表面温度是零下180摄氏度 It is, after all, minus 180 degrees Celsius at the surface,
可是因为各项生命要素都存在 but, because of the presence of all those ingredients,
土卫六若受热 情况或许会迥然不同 it might be a very different story if you warm Titan up.
55亿年后
太阳因为老化而膨胀 In the light of the old expanding sun...
太阳系的最远端地带 ..the far reaches of the solar system
将吸收到更多的太阳能 will receive more solar energy.
土卫六的大气层将会变暖 Titan's atmosphere will begin to warm.
随着温度升高 巍峨的冰山将会融化 变矮 Mountains of ice will shrink and melt as temperatures rise...
其中禁锢的水冰将取代液态甲烷 ..the frozen water they contain replacing the liquid methane.
连绵的群山将会化身汪洋 Mountains will become oceans of water.
太阳系的命运将发生奇特转折 当太阳走向生命的终点时 In a strange twist of fate, at the end the life of the sun...
太阳系的最后一个海洋世界 ..the solar system's last ocean world
很可能会孕育出生命 will wake up to its own biological possibilities.
这颗遥远的卫星将享受短暂的太阳光 This distant moon will enjoy its brief moment in the sun.
人们很容易把宜居性当成各行星的永恒特征 It's easy to think of habitability as a permanent feature
或者说是决定性特征 of a world's defining characteristic, if you like.
地球是一颗生机勃勃的行星 因为它位于适居带内 So the Earth is a living planet because it's in the Goldilocks zone
距离太阳不十分遥远 也不过分接近 around the sun - not too close and not too far away.
但真实情况要复杂得多 But things are more complicated than that.
太阳系充满活力 Solar systems are dynamic places.
行星的轨道可以改变 恒星的亮度也可以改变 Planetary orbits can change and stars can vary in brightness,
昔日的行星天堂也可以变成地狱 so planets that were once heaven can become hell.
我们现在明白地球真的非常幸运 We now understand that the Earth has been a fortunate world,
它在瞬息万变的太阳系 就像一座平静的绿洲 an oasis of calm in an ever-changing solar system,
维持着稳定的气候 在40亿年的时间里 that's maintained a stable climate, perhaps against the odds,
克服种种障碍 促进了复杂生物的进化 for the four billion years it took complex living things to evolve.
我们不清楚茫茫恒星中 We don't know how many planets like Earth there are
有多少个地球这样的行星存在 out there amongst the stars,
在有些地方 太阳系的组成元素 places where the ingredients of solar systems
已经自动形成 have assembled themselves into structures
能够创造出其它世界的结构 that can dream of other worlds,
但是我们必须正视一种可能性 but we have to take the possibility very seriously
也许它不存在 that there might be few.
这使得地球和我们人类变得弥足珍贵 And that would make Earth, and us, extremely rare and precious.
《行星》幕后故事
水星是最神秘莫测的一颗太阳系行星 而且研究难度大 Mercury is the most enigmatic of all the planets and difficult to study.
真正的问题在于它的温度极高 The real problem is that it's really hot.
它距离太阳最近 It's the planet closest to the sun
南希·沙博博士 “信使”号探测器仪器专家
很显然探测水星很具挑战性 and obviously that makes it challenging.
“信使”号建造 2000年初
所以我们必须保护探测器 So you have to protect the spacecraft
免受太阳热量的影响 “信使”号的解决方案就是 from the heat from the sun, and the way Messenger addressed this
拉里·尼特勒博士 “信使”号副首席研究员
在探测器前方安装了一个巨型陶瓷遮阳罩 was to put the whole spacecraft behind a giant ceramic sunshade.
他们装了这个遮阳罩 否则探删器上的设备 It had this sunshade. If it didn't face the sun,
可能早就融化了 it would have melted the instruments, literally.
另一个主要挑战 就是保护探测器 The other major challenge is, you have to protect a spacecraft
免受水星反射的热量影响 from the heat reflected from the planet
我们的解决办法是 and the way we dealt with that
设置椭圆形轨道 was to be in an extremely elliptical orbit,
这样就能近距离掠过北极上空进行观测 where we flew in very close over the North Pole and took observations.
探测器的仪器升温后 我们会飞到 The instruments would heat up and then we'd fly like 10,000km
一万公里外的地方 farther out from the planet...
这时温度会下降 通过这种方式 ..while we cooled off, and, in this way,
我们就能将温度控制在 heat up, cool down and kept everything below
危险水平以下 避免仪器受到损坏 the danger temperatures, where instruments could be damaged.
我负责图像分析组 I was in charge of the camera team.
在前一晚我都没怎么睡觉 I don't think I slept much of the night before.
我急切地想看到第一批传回的照片 I was really anxious to get that first image back.
看到那张传回的照片时 When that image came back,
我们指出所有前所未见的特征 we just started pointing at all the features
然后忍不住说 看看这个 看看那个 that had never been seen before and saying, "Look at this, look at that."
普罗科菲耶夫撞击坑 北极地区
随着时间的推移 探测器近距离飞跃水星北极 Over time, the close-up flights of Mercury's North Pole
使研究小组得以深入观察 allowed the team to peer deep into the shadows
一个特定陨石坑的阴影 of one particular crater.
我们意识到可以想办法 We realised that we could actually design a way
布雷特·德尼维博士 “信使”号地质学家
通过长时间曝光技术来了解 to take a picture using a very long exposure
这些黑暗陨石坑内部的情况 to see inside these dark craters.
“信使”号在设计中 Messenger was designed with instruments
配备了专门用于观察反射比 that could specifically look at their reflectance
和测量氢的仪器 and also measure hydrogen.
我们想那里有很多氢 So we saw, "OK, there's a lot of hydrogen there,"
还有这种奇特的陨石坑来容纳这些冰沉积物 and there was like this fantastic case built for these ice deposits.
不可思议的是 “信使”号探测到 Incredibly, Messenger detected hundreds of billions
北极陨石坑的永久性阴影中 of tonnes of frozen water ice...
居然散布着数千亿吨的水冰 ..scattered in the permanent shadows of the polar craters.
水冰能够保存很长时间 The fact that water ice can survive for a very long period of time
这个事实说明水星几乎是 is a reflection of the fact that the Mercury is rotating
笔直地旋转 所以北极附近有许多陨石坑 almost perfectly straight up, so that there are craters near the pool
这些陨石坑很深 that are so deep and completely shaded
所有阳光都无法照射进去 from sunlight ever hitting them.
所以在那些数十亿年 不见阳光的极地区域 So ice could be stable in those polar regions
水冰或许能保持稳定 that are permanently shadowed for billions of years.
“信使”号探测器已经证明 Messenger had confirmed the existence
在距离太阳最近的水星表面 of an essential ingredient for life...
确实存在构成生命的一个重要成分 ..on the surface at the closest planet to the sun.
“信使”号在最后几圈的运行中燃料耗尽 During Messenger's final orbits, all the fuel was depleted -
我们对此无能为力 there was nothing that we could do -
每次绕轨道运行只会让它更靠近水星 and every orbit just brought it slightly closer to the planet.
一名工程师意识到 One of our engineers realised
探测器上还有氦 that we still had some helium on board the spacecraft
如果在其尾部引燃氦气 它能像燃料一样工作 and, if you blew helium out the back it would work like fuel,
这使我们的水星任务多延长了几周 and that managed to extend us for a few extra weeks.
当然 所有事情都有结束的时候 But, of course, all things have to come to an end.
最后一天许多人都看到了信号 The last day, many of us watched the signal
它绕到水星后面就再没出现 as it went behind the planet and never came back
我们由此知道它坠毁了 and we knew it had crashed
它让我们苦乐参半 and it left us with a real bittersweet feeling,
我们为成功感到高兴 because we were happy at the success,
也为它的终结感到悲伤 but, of course, sad that it was over.
我们为这个神奇的探测器感到骄傲 We all took so much pride in this amazing spacecraft
它执行任务的时间远远超出我们的预期 that lasted way longer than any of us had planned for it to last
它让我们对水星有了更多了解 and that had told us so much about Mercury
并彻底改变了我们看待水星的方式 and really changed the way that we looked at this planet.
下集预告
着陆在红色星球上 Touchdown on the red planet...
将要讲述 ..to uncover...
火星的故事 ..the story of Mars.