美国国家航空航天局“信使”号水星探测器发射升空 Lift off of Messenger on NASA'S mission to Mercury.
水 星
金 星
火 星
木 星
土 星
天 王 星
海 王 星
行星 第2集
火星 距离太阳2.3亿公里
地球的邻居火星是一颗寒冷贫瘠的岩石行星 Our planetary neighbour, Mars, is a cold, barren rock.
火星的表面 因为覆盖着炙热的沙土 呈现出锈红色 Its rusted surface covered in parched sand.
但隐藏在沙尘之下的 But, beneath the dust,
一些痕迹说明火星曾存在生命 the planet bears the scars of a former life.
数十亿年前 火星几乎与地球无异 Billions of years ago, Mars was just like Earth.
那时 火星上厚厚的大气层 A world with a thick atmosphere
为海洋的存在提供了保障 that supported oceans of water.
但如今 这个世界已不复存在 But, today, that world is gone.
火星已死 Mars lies dead,
而地球仍充满生机 while the Earth thrives.
两颗行星的命运如此不同的原因 仍然是不解之谜 Why the two planets had such different fates is a mystery
我们刚刚开始探索其中的奥妙 that we've only just begun to answer.
两颗姐妹行星 地球与火星
火星
你们看到夜空中那个淡红色的光点了吗 You see that pale red point of light in the sky,
就在那边 just there?
那就是火星 That's Mars.
通过小型望远镜观察 它看起来几乎和地球一样 Through a small telescope, it appears almost Earth-like.
19世纪的天文学家 曾在地球的姐妹行星上 Our sister world - polar ice caps and dark surface
观测到极地冰盖和黑色的表面阴影 他们认为这是植被 markings that 19th-century astronomers thought were vegetation,
甚至是将极地融雪水引入干旱的 even canals bringing meltwater down from the poles
赤道城市的河道 to arid equatorial cities.
赫伯特·乔治·威尔斯曾写道 Across the depths of space,
在太空的深处有居民嫉妒地注视着我们 the inhabitants watched us "with envious eyes", wrote HG Wells.
我们现在知道火星上并没有生命在注视我们 We now know that there are no eyes looking back at us.
火星是一个寒冷 干旱的沙漠世界 Mars is a frozen, arid desert world.
但太空探测器的观测结果表明 But a fleet of spacecraft have revealed
情况并非一直如此 that it hasn't always been that way.
“水手”4号探测器成功发射 Mariner 4 was successfully launched on time
“水手”4号探测器 1964年
开启具有历史意义的228天火星之旅 for its historic 228-day journey to Mars.
1965年7月15日 “水手”4号开始回传照片 Picture information started to come in on July 15th, 1965.
首张火星表面清晰图像
这个突破可与伽利略首次通过望远镜 A revelation comparable to Galileo's first view
观测到月球相媲美 of the moon through a telescope.
“水手”4号短暂飞过火星上空 During its brief flyby,
首此为我们传回了火星的近景照片 Mariner 4 gave us our first close-up glimpses of Mars.
“水手”9号探测器 1971年
当“水手”9号探测器进入环绕火星的轨道时 When Mariner 9 was placed into an orbit around Mars,
火星正被一场巨大的沙尘暴笼罩 it saw a planet blanketed by a gigantic dust storm.
在近一年的绕轨运行 In nearly a year of operation,
“水手”9号传回了7000多张照片 they transmit more than 7,000 photographs.
“水手”9号在轨道上拍到了80%的火星表面 From orbit, Mariner 9 photographed 80% of the Martian surface.
维京计划 1975年
首先 它有两只眼睛 可以拍摄到彩色的立体照片 First of all, there are two eyes, not only in colour but also
同时它还带有红外线光储仪 in stereo, and in the infrared part of the spectrum.
它有触觉和听觉 It has a sense of touch, it has a sense of hearing,
但这台探测器最重要的特点是它的大脑 but by far the most important feature of the lander is its brain.
“维京”号探测器首次将我们带到 The Viking programme took us down to the ground
火星表面 for the first time...
“维京”号在火星安全着陆
着陆 我们着陆了 Touchdown, we have touched down.
它揭示了一个 ..and revealed Mars...
完美着陆 Perfect set-down.
前所未见的火星 ..like never before.
这是传回的第一条信息 There is the first piece of information coming in.
火星表面的首张彩色照片
利用过去50年收集的数据 我们可以绘制出 The data gathered over the last 50 years has allowed us to create
火星表面的详细图像 detailed maps of the Martian surface...
并尝试拼凑出它的过去 ..and begin to piece together its past.
火星的地图就像一本本故事书 Maps of Mars are like storybooks.
你可以读到写在火星表面的历史 You can read the history of the planet
这是因为它基本没有被腐蚀 written across its surface, and the reason for that is that there's
数十亿年来 火星表面一直没有被腐蚀 virtually no erosion, hasn't been for billions of years,
因此40亿年前留下的痕迹 so the scars of events that happened even four billion years ago
依然清晰可见 can still be seen.
这种地图被称为地形高程图 This is a type of map called an elevation map.
不同的颜色对应火星表面不同的高度 The colours correspond to difference in heights on the surface,
蓝色表示高度较低 so blue means low
红色或白色表示较高 and red and whites are high.
这个区域的高度大于火星其它区域的平均高度 Now, this region here, which is much higher on average than the rest
被称为塔尔西斯 这里被火山覆盖 of Mars, is called Tharsis and it's covered in volcanoes,
包括太阳系最大的火山 奥林匹斯山 including the largest volcano in the solar system, Olympus Mons.
奥林匹斯山
塔尔西斯的另一侧 是宽大延展的水手谷 At the other side of Tharsis is the great Valles Marineris,
在这个峡谷面前 地球上所有的峡谷 the Mariner Valley, and it is a canyon that dwarfs
都相形见绌 anything we see on Earth.
水手谷
火星的另一侧是一个被称为赫拉斯盆地的冲击盆地 On the opposite side of the planet is an impact basin called Hellas.
赫拉斯盆地
从火山口边缘到火山口底部的高度差 The height difference from the crater rim
是9000米 to the crater floor is 9km.
这意味着我们可以将珠穆朗玛峰放在它的中间 That means you could fit Everest in the middle of there
还可以俯瞰珠穆朗玛峰的顶峰 and look down on its summit.
盆地周围的地区揭示了火星过去存在生命的迹象 And the region surrounding the basin reveals Mars' former life.
赫拉斯盆地也是火星存世最古老的地带 遭受冲击形成的 The Hellas basin is punched into the oldest-surviving terrain on Mars.
这片地形被称为诺亚台地 It's called Noachis Terra
或诺亚之地 or The Land Of Noah.
这个名称非常形象 因为它的表面是由流水 And that's a wonderfully evocative name because its surface is sculpted
雕蚀而成的 by flowing water.
诺亚台地
我们在最古老的火星表面发现了 All across the earliest Martian surface, we've glimpsed traces
湖泊和河流的痕迹 of what appear to have been lakes and rivers.
新一代的太空探测器被送往火星 And so a new generation of spacecraft has been sent to Mars,
美国国家航空航天局 “火星大气与挥发物演化”探测器大气分析
探索火星上是否存在水 to investigate the existence of water...
美国国家航空航天局 火星勘测轨道飞行器拍摄火星表面
这里又发生过什么 水会消失不见了 ..and what happened to the planet for it all to disappear.
这是史上最大胆的火星任务 Led by the most audacious Mars mission ever attempted...
我们在火星轨道附近遭遇了两次冲击 We have two-way Doppler and orbit around the planet Mars.
美国国家航空航天局“好奇”号火星探测器
将一吨重的探测器送到火星表面 ..to land a one-tonne rover on the Martian surface.
最后它经受了著名的“恐怖七分钟” Its final descent has become known as the "seven minutes of terror".
“好奇”号火星探测器成功登陆盖尔撞击坑 Curiosity touched down in Gale crater,
盖尔撞击坑的宽度为150公里 a 150-kilometre-wide impact basin,
科学家认为这里曾存在一个古老的湖泊 thought to have been home to an ancient lake.
“好奇”号火星探测器耗资25亿美元 是一个移动的化学实验室 The rover is a 2.5 billion mobile chemistry lab...
它的任务是在火星表面提取样本 ..designed to take samples of the Martian surface
并分析样本成分 and analyse its composition.
“好奇”号在探索撞击坑的同时 发现了被水流 As it explored the crater, Curiosity saw pebbles polished
磨光磨圆的鹅卵石 and rounded by running water
这里曾是河水流经之地 in what had once been rivers and streams.
“好奇”号在着陆61天后 找到了理想的地点 Then, 61 days after landing, Curiosity identified the perfect
开始实施它的首要任务 spot to begin its primary mission.
撞击坑里有一块名为“岩巢”的沙地 In a sandy area of the crater called the Rocknest,
探测器在这里首次收集到了火星的土壤 the rover took its first scoops of Martian soil.
探测器对这些细沙进行化学分析 Chemical analysis of the fine, dusty sand revealed
并有了令人意外的发现 something quite unexpected.
尽管火星表面看起来完全干燥 Even though the surface of Mars appears completely dry,
但土壤中仍有2%的成分是水 2% of the soil is still made up of water.
“好奇”号发现的证据表明 Curiosity had found evidence of just how wet a planet
火星曾是一颗湿润的行星 ancient Mars had been.
数十亿年前 For hundreds of millions of years,
火星 40亿年前
火星曾是一个水世界 Mars was a water world.
这里雨水充沛 Rains fell,
河流奔腾 rivers ran,
而在北半球 and, in the northern hemisphere,
雨水汇聚成一个巨大海洋 water collected in a vast sea
覆盖了火星表面的五分之一 that covered a fifth of the Martian surface.
这颗红色行星曾经也呈现着蓝色 The Red Planet was once blue.
所有证据表明 约40亿年前 All the evidence suggests that there were large bodies
火星上曾存在大量的水 of standing water on Mars around 4 billion years ago,
当时的大气压力与地球目前情况相当 and the atmospheric pressure was at least that of Earth today,
甚至更高 perhaps even higher.
气温约为25摄氏度 在那个时候我也许完全可以 Temperatures were around 25 degrees, so I could have sat on Mars
坐到火星上 可能需要戴个呼吸面罩 all those years ago, admittedly with a mask to breathe,
因为那里的氧气很稀薄 但我可以坐在那里 because there was very little oxygen, but I could have sat there
欣赏到这样的风景 and looked out over a view like that.
所以我们不必只去想象火星曾经的样子 So, you don't have to imagine what Mars was like in the past.
我们可以真切地体验到 You can experience it.
就像现在这样 It was pretty much like this.
但在后来的10亿年间 But, within a billion years,
火星上的湖泊和海洋全部消失了 all Mars' lakes and seas had disappeared.
太阳系中 只剩下唯一一颗蓝色的星球 In our solar system, only one blue planet survives...
那就是火星的姐妹行星 地球 ..Mars' sister, Earth.
地球表面的70%被海洋覆盖 70% of our planet's surface is covered by ocean.
成百万的物种在海洋中繁衍生息 Under the waves, a million species thrive.
在陆地上 雨水维系着地球微妙的生态系统 While on land, the rains support Earth's delicate ecosystems...
为大量的生命提供家园和庇护 ..providing a home for an abundance of life.
但它并非一直如此 But it hasn't always been this way.
地球 40亿年前
早期的地球与我们今天所知的地球不同 The early Earth was unrecognisable from the planet we know today.
早期地球大气中的二氧化碳浓度很高 Its atmosphere thick with carbon dioxide.
地球上的海水呈酸性 And its oceans acidic.
40亿年前 地球曾是一个有毒的混乱世界 Four billions years ago, Earth was a troubled, toxic world...
而当时的火星正在蓬勃发展 ..while Mars was flourishing.
但两颗行星都将被太空的 But both planets were about to be engulfed
一场大灾难吞没 by a cataclysm from space.
为了了解当时的情形 To understand what happened,
我们必须将眼光投向地球以外的地方 we have to look beyond our own world.
仅观察地球表面 是无法去解读 You can't read the deep history of the Earth by looking
其久远历史的 因为地球的地质活动频繁 at its surface because our planet is a geologically active world.
由于火山活动 风化作用和海洋的作用 The surface is constantly being reshaped by volcanic activity,
地球表面不断地发生变化 但我们有一位同伴 weathering, and the actions of the oceans, but we have a companion,
那就是月球 数十亿年来 月球一直不活跃 the moon, which has been inactive for many billions of years,
因此太阳系在这个区域发生的一切 and so the history of events that happened in this region
都被记录在了月球的表面 of the solar system is written all over its surface.
遍布陨石坑是月球表面最显著的特点 The most distinctive feature of the moon's surface
月球表面记录下了所有来自太空的撞击 are its craters - it is literally covered in a record of impacts
我们可以据此分析月球不同部分的 from space, and that allows us to estimate the relative ages
相对年代 of different parts of the moon.
很简单 Quite simply, if there are more craters,
陨石坑更多的区域一定更古老 then that piece of the moon must be older.
这说明它被撞击的次数更多 There's been more time for the impacts to build up.
但除了判断相对年代 我们还可以做得更多 But we can do better than just measure the relative ages
因为我们还有岩石 阿波罗号宇航员 because we have rocks, the moon rocks brought back
带回来的月球岩石 by the Apollo astronauts.
我们可以分析岩石内部放射性元素的衰变速度 We can estimate the ages of rocks very precisely by looking
非常准确地判断岩石的年龄 at the rates of decay of radioactive elements inside them.
它们就像小小的秒表 从岩石形成的那一刻 They're like little stopwatches that start ticking the moment
开始滴答作响 这些都是太空撞击带来的 the rocks are formed, in this case by the impacts from space.
因此我们可以将某个月球区域的 So, the moon rocks allow us to tie the number of craters
陨石坑数量 in a particular region of the moon
和岩石的绝对年龄联系起来分析 to an absolute age measured by the rocks.
这不仅能帮助我们确定月球表面受到撞击的时间 And this doesn't just allow us to date impacts on the lunar surface.
毛德陨石坑
哈德利陨石坑
我们还能通过陨石坑 It means that craters can be used
分析太阳系的演化历史 to read the histories of worlds across the solar system.
涅库姆陨石坑
也包括火星的历史 Including Mars.
当我们将所有数据集中在一起 我们有了惊人的发现 When we gathered all the data, we discovered something surprising.
约38亿到39亿年前 陨石坑形成的速度 There was a peak in the crater formation rate, about 3.8
达到峰值 to 3.9 billion years ago,
这表明整个太阳系内在这个时期出现了剧烈的天体撞击 which signified a period of intense violence in the solar system,
这被称为晚期重大撞击事件 and that is called the Late Heavy Bombardment.
火星 39亿年前
无数小行星冲进火星的大气层燃烧解体 Countless asteroids fragmented in Mars' atmosphere,
给整个火星带来了一场浩劫 raining havoc across the planet.
据估计 在火星表面 It's estimated that 53 tonnes of rock
每平方米有53吨岩石落下 fell on every square metre of Mars.
超过三分之一的火星表面伤痕累累 Over a third of the planet's surface was obliterated...
火星被推到了死亡的边缘 ..and Mars was pushed to the brink of death.
月球表面的证据告诉我们太空曾发生 Whilst the evidence from the surface of the moon tells us
晚期重大撞击事件 但并未揭示其中的原因 that the Late Heavy Bombardment happened, it doesn't tell us why.
为此 我们需要通过计算机模型 For that, we have to resort to computer models of the evolution
来还原太阳系的演化过程 在研究中 of the solar system, and, when we do that,
我们发现根源来自海王星 they point the finger at Neptune.
人们认为海王星在向外迁移时经过了柯伊伯带 It's thought that Neptune migrated outwards into the Kuiper belt...
无数冰质岩石天体集中在这里 ..a region of icy, rocky objects
运行于太阳系的边缘地区 orbiting at the edge of the solar system.
天体间由此产生的相互引力破坏了这些轨道 The resulting gravitational interactions disrupted those orbits
并将很多天体推向太阳系的内部 and sent many of the objects inwards to the inner solar system,
这很可能导致了晚期重大撞击事件的发生 and that may have been the cause of the Late Heavy Bombardment.
地球 39亿年前
地球当时也遭受了猛烈的撞击 Earth also suffered the onslaught,
在此后的数千万年里 and, for tens of millions of years,
这两颗姐妹行星的命运一直悬而未决 the fortunes of the two sister worlds hung in the balance.
但就在这种最不乐观的条件下 But, just when conditions appeared at their least promising,
地球最重要的特征出现了 Earth's most precious characteristic emerged.
生命 Life.
有充足的证据表明 约38亿年前 There is good evidence that life was present on Earth
地球就已出现生命 我认为可以排除 around 3.8 billion years ago, and discounting the - I think -
那种最小的可能性 就是生命起源于 remote possibility that life began elsewhere
太阳系的其它地方 又被陨石或彗星 in the solar system and was transported to the Earth
带到地球的说法 on meteorites or comets,
那么可以说生命一定是从地球开始的 that means that life must have begun here.
在这颗行星的某个地方产生了 So, somewhere on this planet there was a transition
由地球自身的化学变化 from geochemistry - the chemistry of Earth,
转变为了生物化学的演变 to biochemistry - the chemistry of life.
但这样的转变到底是如何产生的 And whilst the precise details of how that transition occurred
至今仍是个迷 人们认为温暖的火山池 remain a mystery, it's thought that in warm volcanic pools
或深海热泉口最适宜构成 or deep sea hydrothermal vents, conditions were right
生命的基本化学单位自发形成 for the chemical building blocks of life to form spontaneously.
这意味着 如果太阳系的其它地方 And that means that if similar conditions
也存在相似的条件 were to be found elsewhere in the solar system,
就也有可能诞生生命 it might be possible that life began there too.
阿特拉斯-5运载火箭点火升空 Ignition, and lift off of the Atlas V rocket with MRO.
火星勘测轨道飞行器
火星勘测轨道飞行器发射成功 Surveying for the deepest insights
开始深入探索火星的神秘演变 into the mysterious evolution of Mars.
2005年 美国国家航空航天局开始了 So, in 2005, NASA embarked on a mission to look
在火星寻找相同环境的任务 for those same environments on Mars.
火星 现在
10多年来 火星勘测轨道飞行器 For more than a decade, the Mars Reconnaissance Orbiter
一直在关注这颗红色星球 has been our eyes on the Red Planet...
美国国家航空航天局 火星勘测轨道飞行器
它传回的数据 ..sending back more data
它传回的数据远多于其它火星任务传回的数据之和 than all the other Mars missions combined.
火星勘测轨道飞行器拍摄了6万多张图片 MRO has made more than 60,000 orbits,
覆盖了99%以上的火星表面 mapping over 99% of the planet's surface.
它的高分辨率摄像机揭示了一个前所未有的火星 Its high-resolution cameras have revealed Mars as never before,
人们发现了极地雪崩 discovering polar avalanches,
以及流动的沙丘 shifting sand dunes...
还有沙漠 甚至液态雪融水的季节性流动 ..and what could be seasonal flows of sand or even liquid meltwater.
2017年 火星勘测轨道飞行器开始关注 Then, in 2017, MRO turned its gaze
红色星球最古老的特征之一 to one of the Red Planet's oldest features,
波江盆地 the Eridania Basin.
波江盆地 38亿年前
38亿年前 这个盆地还是一片汪洋 3.8 billion years ago, the basin was a vast sea...
这里的水容量 ..holding ten times more water
是北美五大湖区水容量的10倍 than the Great Lakes of North America.
火星勘测轨道飞行器在这里发现了找寻已久的证据 And it was here that MRO found the evidence it was looking for.
400米厚的矿物沉积 这通常形成于 400-metre-thick deposits of minerals that, on Earth,
地球的深海热泉口 form in deep sea hydrothermal vents.
在波江盆地 火星勘测轨道飞行器发现 In the Eridania Basin, MRO revealed that conditions on Mars
火星出现过适合孕育生命的条件 had once been ripe for the emergence of life.
我们无法确切知道火星上是否出现过生命 或这些生命是否仍然存在 We won't know for sure whether life began or even perhaps still exists
除非前往火星并找到实物证据 on Mars until we go there and find physical evidence -
微生物或许就深埋于液态水绿洲的土壤之中 so, microbes buried deep below the soil in oases of liquid water,
或者会存在微生物化石 但我们知道 or maybe microbe fossils - but what we do know is that,
35亿年前 地球开始出现生命时 when life began here on Earth, 3.8 billion years ago,
火星的条件与地球非常相似 the conditions on Mars were very similar.
火星上也有海洋 有火山活动 There were seas, there was volcanic activity,
甚至火星上的海底也存在深海热泉 there were even hydrothermal vent systems on the floors of its oceans.
至少有可能的是 地球并不是太阳系 So, it is at least possible that Earth is not the only world
唯一有生命开始的星球 in the solar system where life began.
火星在诺亚时代 The habitable conditions during what's known
出现的宜居条件持续了数亿年 as Mars' Noachian era persisted for hundreds of millions of years.
但红色星球的生命发展前景突然改变 But then, prospects for life on the Red Planet changed dramatically.
在大约35亿年前 诺亚时代结束 Around 3.5 billion years ago, the Noachian era drew to a close
火星进入了更寒冷和干旱的时期 即赫斯伯利亚纪时期 and Mars entered a more frozen, arid phase, known as the Hesperian.
曾经在诺亚时代 在火星表面自由流动的水 The water that flowed freely over the surface during the age of Noah
被封锁在了巨大的冰库里 became locked away in giant reservoirs of ice.
但是就在这个时期 火星的火山活动更加活跃 But, around the same time, Mars became more volcanically active,
火山爆发和地下熔岩流 and the volcanic eruptions and sub-surface lava flows
偶尔会融化冰层 导致灾难性的洪水 occasionally melted the ice, leading to catastrophic flooding.
这一定是太阳系中 They must have been some of the most spectacular sights
当时最为壮观的景象 in the history of the solar system.
火星 35亿年前
当熔岩向上推动地壳 As molten rock pushed upwards through the crust,
融化的冰水涌向火星表面 meltwater poured out onto the surface.
洪水从南部的高地肆虐而下 It raged down from the southern highlands...
一直来到一个被称为艾彻斯深谷的地方 ..until, in a place known as Echus Casma, it plunged
它从4000米高的悬崖俯冲而下 over cliffs 4km high...
这形成了太阳系史上 ..creating the largest waterfall
最大的瀑布 the solar system has ever seen.
艾彻斯深谷绝不同于地球上的任何瀑布 Echus Casma would have been like no waterfall ever seen on Earth.
35万立方公里的水流过这里 350 cubic kilometres of water flowed over it.
就像一个长宽高均为70公里的立方体 That's like a cube 70km by 70km by 70km.
所有的水流到宽10公里 It all entered into a canyon 10km wide
长100公里的山谷里 而这一切就发生在几周内 and 100km long, and that happened in a few weeks.
一旦洪水平息 水就消失了 Once the flood subsided, the water disappeared...
火星表面只留下了洪水侵蚀的痕迹 ..leaving the evidence of the falls etched into the face of the planet.
艾彻斯深谷
我们不知道火星为何会从温暖潮湿的气候 We don't know precisely why the climate of Mars changed
转变成寒冷干旱的气候 from warm and wet to cold and arid.
我们讨论的是35亿年前 We're talking about events that happened
发生在数亿公里外的一颗行星上的事件 three and a half billion years ago on a planet hundreds of millions
这是一个很难的课题 of kilometres away, so it is a hard problem.
但我们强烈怀疑 火星表面 But we do strongly suspect that changes happening
之所以会发生变化 on the planet's surface were driven
至少有一部分原因来自于火星内部的变化 at least in part by changes in the planet's interior.
火星的核心深处发生的一些变化 Deep within Mars' core,
很可能导致了这颗行星的死亡 something was causing the planet to die...
我们可以从火星的大气层中找到证据 ..and the evidence can be found in Mars' atmosphere.
倒计时 10 9 8 7 6 T-minus ten, nine, eight, seven, six,
5 4 3 five, four, three,
火星大气与挥发物演化任务
2 1 two, one.
主发动机开始启动 点火 搭载“火星大气与挥发物演化”探测器的 Main engine start, ignition, and lift-off
阿特拉斯-5型运载火箭发射 of the Atlas V with MAVEN,
执行任务 在火星的大气层 looking for clues about the evolution of Mars
寻找火星演变的线索 through its atmosphere.
2014年9月 美国国家航空航天局的“火星大气与挥发物演化”探测器 In September 2014, NASA'S MAVEN probe made its final
最后一次靠近火星 approach to the Red Planet.
它的任务是调查火星 Its mission - to understand what drove the planet's
气候变化的原因 dramatic climate change.
“火星大气与挥发物演化”探测器配备有一系列仪器 MAVEN is equipped with an array of instruments designed to measure
可分析火星大气中原子和分子的变化 the behaviour of the atoms and molecules in Mars' atmosphere.
探测器沿着一个椭圆轨道绕火星飞行 The spacecraft circles Mars in an elliptical orbit...
它的任务是全面了解 ..allowing it to measure the full profile
火星外层大气的状况 of the planet's upper atmosphere.
它的最低点 At its lowest point,
距离火星表面仅150公里 it's just 150km above the surface.
最高点则会超过6000公里 At its highest, a little over 6,000 kilometres.
“火星大气与挥发物演化”探测器在火星大气层的最顶端 And it was at the very top of Mars' atmosphere that MAVEN found
发现了火星发生变化的原因 the key to the mystery of what happened to Mars.
详细的测量分析表明 Detailed measurements revealed gas is being lost
火星大气中的气体正在消失 from the Martian atmosphere,
以大约 escaping to space
每秒两千克的速度散失到太空中 at a rate of about two kilograms every second.
人们认为在漫长的时间里 火星大气的逐渐散失 Over time, it's thought this gradual stripping away of Mars' atmosphere
致使围绕火星的绝缘层慢慢变薄 has slowly thinned the insulating layer surrounding the planet...
最终导致了火星表面温度的急剧下降 ..causing surface temperatures to plummet.
然而是什么原因导致火星大气消失 But what was it that caused Mars to lose its atmosphere
而地球的大气会稳定存在呢 while Earth clung on to hers?
在距离这里1.5亿公里的地方 就是我们看到的落日 150 million kilometres away in that direction is the setting sun,
这是一个巨大的核聚变反应堆 a giant nuclear fusion reactor.
可容纳100万个地球 You can fit one million Earths inside it.
它的表面温度 Now, the surface temperature
约为6000摄氏度 is only around 6,000 degrees Celsius,
但太阳大气 也就是日冕的温度 but the sun's atmosphere, known as its corona,
可达100万摄氏度 is at one million degrees.
这意味着它以所谓的等离子体形式存在 And that means it's in the form of what's known as a plasma, a soup
一种带电粒子的混合物 of electrically charged particles.
如今一些粒子快速移动 以太阳风的形式 Some of those particles are moving around so fast that they can escape,
从太阳表面逃逸 and they stream away in what's known as the solar wind.
它们会以每秒几百公里的惊人速度到达地球 They reach the Earth travelling at a few hundred kilometres per second.
如果不加以保护 它们就会吹走我们的大气 And, if we weren't protected, they would strip away our atmosphere.
当太阳落到地平线以下时 And when the sun dips below the horizon...
具备保护性的力场有时会在夜空中出现 ..there are times when that protective force field is revealed.
看那边 Just look at that!
那就是美丽的极光 I mean, there is the aurora.
这是大自然的杰作 它们呈现于天空之上 It's the laws of nature, all of them, written across the sky.
来自恒星内部核聚变反应堆的带电粒子 Electrically-charged particles have been driven away from the sun,
从太阳的表面逃逸 ultimately from nuclear fusion reactions in the core of a star.
它们穿过太阳系 撞击地球磁场 They're crossing the solar system, hitting the Earth's magnetic field,
将地球磁场延伸至地球的阴暗面 stretching it out on the dark side of the planet.
然后磁场像橡皮筋一样弹回来 The field then snaps back like an elastic band,
使所有带电粒子沿着两极的磁场线 accelerating all of those charged particles up and down
上下加速 就在这里 在冰岛的上空 the field lines to the poles, which is here in the skies
当带电粒子撞击大气中的 over Iceland, and they hit nitrogen
氮气和氧原子时 and oxygen molecules in the atmosphere.
你将看到量子力学的产生 它们使原子兴奋 And you're seeing quantum mechanics - they're exciting the
使原子发出带有特殊颜色的光 molecules so that they emit light in characteristic colours.
这是我们看到地球磁场的 And, if you think about it, this is the only time
唯一机会 that we really see the Earth's magnetic field.
这是地球生命 It's one of the reasons why life on Earth
得以延续40亿年的原因之一 has been able to persist for four billion years.
所以在某种意义上 这也是我们存在的原因 In a sense, that's the reason that you exist.
地球磁场保护了地球大气 It's Earth's magnetic field that protects our atmosphere
不被太阳风破坏 from the ravages of the solar wind,
这种保护盾的形成 and that protective shield has its origins deep
起源于地球的内部深处 in the planet's interior.
在我的脚下几千公里的地方 Thousands of kilometres down below my feet,
你的脚下也是一样 就是地球的外地核 actually below your feet now, is the Earth's outer core,
它是一团沸腾的铁水 which is a seething mass of molten iron.
内部产生的对流能使铁水上升 Convection currents cause the molten iron to rise,
而地球自转使铁水也会跟着旋转 and then the Earth's rotation causes it to spiral around.
此时导电液体的螺旋流动 Now, a spiralling, circling flow
就像一台发电机 of an electrically conducting liquid is a dynamo.
这台发电机能够产生磁场 地球磁场不仅能上升到 A dynamo generates a magnetic field and the Earth's field rises up,
地球表面 同时也存在于外太空 not just to the surface here, but out into space,
对地球形成了保护盾 forming our protective shield.
也就是我们看到的这一切 And that is what you see there.
和地球一样 And just like Earth,
古老的火星也曾拥有隔离太阳的保护盾 ancient Mars was also shielded from the sun.
极光曾在火星的两极跳跃 Aurora once danced above its poles...
保护火星的大气和大气之下的海洋 ..keeping guard over the Martian atmosphere and seas below.
但在35亿到40亿年前 But between 3.5 and 4 billion years ago,
火星的发电机关闭了 Mars' dynamo switched off.
随着磁场的减弱 两极附近的极光 The aurora surrounding the poles slowly faded away
慢慢消失 as the magnetic field diminished...
于是火星大气开始被太阳风 ..allowing the atmosphere to be stripped away
吹离 by the solar wind.
失去保护的海洋蒸发 地表结冰 Without protection, seas evaporated, the surface froze,
火星的地貌完全改变 and Mars was transformed.
地球 35亿年前
与此同时 火星的姐妹行星的命运 At the same time, the fortunes of Mars' sister world
即将发生截然不同的变化 were about to take a very different turn.
在接下来的10亿年里 For the next billion years or so, Earth was indistinguishable
地球和火星的早期地貌没有区别 from those landscapes of early Mars-
即一片被海洋包围的贫瘠大陆 barren continents surrounded by ocean.
但在地球的海洋中 生命开始改变地球 But in Earth's oceans, life was beginning to transform the planet.
原始海藻开始中和海洋的酸度 Primitive algae started to neutralise the ocean's acidity
并且用氧气替代红色浓雾 and replace the dense red fog of Earth's methane-rich
即富含甲烷的地球大气 atmosphere with oxygen.
约6亿年前 富含氧气的大气使复杂的生命 Around 600 million years ago, that oxygen-rich atmosphere allowed
得以在海洋进化 在陆地繁衍生息 complex life to evolve in the oceans, colonise the land,
并最终产生了如今这个充满生机的世界 and ultimately produce this almost-infinitely rich living world
而我们正是这个世界的一部分 today, of which we are a part.
火星死去 但地球欣欣向荣 While Mars died, Earth flourished.
为了解两颗姐妹行星为何命运如此不同的原因 To understand why the two sisters had such different destinies,
我们必须回到 you have to go right back
两颗行星的形成之初 to the time the planets were forming.
太阳系 45亿年前
在火星和地球诞生时 When Mars and Earth were born,
太阳系还是由气体和岩石组成的混沌旋涡 the solar system was a chaotic vortex of gas and rock.
物质聚集在一起 逐渐变大 然后又会被撞碎 Material clumped together and grew, only to be smashed apart.
随着时间的推移 有些物体变得足够大 Over time, some of the objects became large enough to survive
可以承受较小的撞击 并继续变大 at least the smaller impacts, and continued to grow,
这包括胚胎期的地球和火星 including the embryonic planets Earth and Mars.
但两颗行星有一个重要的不同 But there was one crucial difference between the young planets.
火星形成于太阳系中 Mars formed in a region of the solar system
岩石物质相对较少的区域 with considerably less rocky material.
这对行星的生长产生了深远的影响 And that had a profound impact on the planet's growth.
相对来说 火星要小很多 它的直径约为地球的一半 Mars is a significantly smaller world - it's about half the diameter
这也是两颗行星产生差异的原因 of the Earth, and that makes all the difference.
尽管我们并没有完全了解其中的细节 Although the details are not yet fully understood,
但可以明确的是 由于火星体积更小 导致它的发电机 it seems clear that Mars' smaller size meant that its dynamo switched
在数十亿年前关闭了 off many billions of years ago.
体积更小意味着火星的核心比地球的核心冷却得更快 Being smaller meant Mars' core cooled more quickly than Earth's.
这显然也是火星失去磁场的 And this is certainly part of the reason why Mars
原因之一 lost its magnetic field.
尽管火星与太阳的距离大于地球与太阳的距离 Even though the planet is further away from the sun than we are,
但太阳风带走了它的大气 that meant that the solar wind stripped away its atmosphere
火星死了 and Mars died.
因此 即使地球和火星在很多方面都很相似 So, even though Earth and Mars are so similar in so many ways,
二者在太阳系的位置和大小导致了 the difference in position and size in the solar system
它们完全不同的命运 led to very different fates.
很久以前 两颗姐妹行星诞生 Long ago, two sister worlds were born.
童年时期的火星温暖湿润 In childhood, Mars was warm and wet...
而地球荒凉且充满毒气 ..whilst the Earth was inhospitable and toxic.
两颗年轻的行星都在晚期重大撞击事件中 Both young planets survived the violence
活了下来 of the Late Heavy Bombardment,
并成为成熟的行星 emerging as mature worlds,
具备了生命所需的所有要素 primed with all the ingredients for life.
但那颗小一些的行星的核心深处正在消亡 But deep inside, the smaller of the two was dying.
火星的海洋干涸 Mars' seas dried up.
随着火星内部的冷却 它的火焰也接连熄灭 And as the planet's interior cooled, one by one her fires went out.
奥林匹斯山是太阳系最大的火山 Olympus Mons, the largest volcano in the solar system,
它的最后一次喷发是在大约2500万年前 last erupted around 25 million years ago.
随着熔岩变成岩石 As the lava turned to stone,
火星被时间冻结 Mars was frozen in time.
因此 直至今日 它的表面依然满目疮痍 布满沙尘 And so, today, her surface lies rusted and gathering dust.
但这也许并不是火星故事的结局 But that might not be the end of Mars' story.
因为下一代太空探测器正在行动 Because the next generation of spacecraft are already on their way.
美国国家航空航天局猎户座飞船
美国国家航空航天局的猎户座飞船目前正在进行高级测试 NASA Orion - currently in advanced testing.
可搭载4名宇航员
比以往任何时候更深入太空
欧洲太空局“火星生命”
欧洲太空局的 ESA ExoMars -
“火星生命”探测联合任务旨在寻找火星的生命迹象 a fleet of spacecraft designed to search for signs of life.
这是有史以来最具野心的私人太空计划 And the most ambitious private space mission ever conceived.
美国太空探索技术公司 重型猎鹰火箭
世界上最强大的火箭
科学家研发出可将人类送往火星表面的运载火箭 A launch vehicle developed to take humans to the surface of Mars.
火星在某种意义上是一个失败的世界 Mars is, in a sense, a failed world,
它是一抹褪色的余烬 上面镌刻着代表火星迷人过去的记忆 a faded ember etched with the memories of a more enticing past,
但火星上曾经有过 也许仍有生命存在 but there may have been, and may still be, life on Mars.
同时 在太阳系发现第二种生命形式 And the discovery of a second genesis in our solar system
将产生深远的哲学 科学和文化影响 would have profound philosophical, scientific and cultural consequences
因为这意味着生命起源 because it would mean there is a sense of inevitability
存在必然性 about the origin of life,
这意味着宇宙中 and that would mean that the universe
可能会充满生命 我们并不孤单 is most likely teeming with life - that we are not alone.
但我认为同样重要的是 像火星这样历史久远的行星 But equally importantly, I think, is the role that a planet
在未来可能发挥的作用 with a history like Mars could play in our future.
火星上资源丰富 它的地下蕴藏着 Mars is rich in resources, it has vast reservoirs of frozen
丰富的冰冻水 还有矿物质 water below the surface, and minerals -
像铁 氮 碳 氧 这些都是 iron, nitrogen, carbon, oxygen - all the things
文明发展所需的要素 you need to support a civilisation.
因此我认为 在我有生之年 And that's why I think that, in my lifetime,
将出现火星人 火星人就是我们 there will be Martians, but the Martians will be us.
我们将前住火星定居 We will go to Mars and make it our home,
这颗古老的红色星球将成为我们人类走出地球 and that old red world will become our first step
实现星际漫游的第一步 beyond the cradle, and out to the stars.
《行星》幕后故事
火星确实激发了 Mars really captures
詹妮弗·艾根博德博士 美国国家航空航天局戈达德太空飞行中心
我们的想象力 our imagination,
部分原因是它离地球很近 partly because it's so close.
我认为人类对火星非常感兴趣 是因为 I think people are really interested in Mars because it actually
约翰·格勒青格教授 加州理工学院
它与地球很相似 is so similar to Earth.
火星离地球很近 我们可以带着机器人和飞行任务 It's close by, it's easy to travel there with robots
前往火星 事实上我们已经进行过很多探索 and space missions, and so we've done a lot of exploration.
每次前往火星都会有新的发现 And, every time you go and look, you discover something new.
美国国家航空航天局于2011年11月26日发射“好奇”号火星探测器 NASA Curiosity launched on the 26th of November, 2011.
但科学家面临的最大难题 But the biggest obstacle facing the mission team
不是如何离开地球 wasn't leaving the Earth.
与我们通过太空探测器前往的其它地方相比 Mars has a unique set of challenges
火星给我们带来一系列独特的挑战 compared to other places we go with spacecraft.
阿什温·瓦萨瓦达博士 美国国家航空航天局喷气推进实验室
火星有大气层 但它很稀薄 不足以 Mars has an atmosphere but it's thin, so it's not enough
让我们的速度慢下来 to really slow you down,
但在我们试图着陆时又足以让我们燃烧起来 but it is enough to actually burn you up as you're trying to land.
“好奇”号以每小时两万公里的速度 Curiosity reached the top of the Martian atmosphere,
抵达火星大气层的边缘 travelling at 20,000km per hour.
“好奇”号是一个巨大的探测器 它重达一吨 Curiosity is a big rover. It weighs a metric ton,
因此要让它成功着陆 and so landing that required every trick in the book
我们必须从以往的任务中学习着陆火星的所有技巧 of how we've learned to land on Mars with previous missions.
为了安全着陆 “好奇”号必须将速度减到 To land safely, the rover had to be slowed
每小时4000公里以下 to less than 4km per hour.
航天器到达火星时的速度很快 You end up arriving at Mars going really fast,
因此必须减速 so you actually have to slow down,
我们通过一个防热罩实现减速的目的 and we do that using a heat shield,
航天器会燃烧很多燃料 产生大量热量 which burns off a lot of energy and creates a lot of heat,
因此我们必须吸收这些热量 防止损坏航天器 so you have to absorb that somehow and not damage the spacecraft.
接下来 降落伞登场 Then a parachute comes out.
这是我们在行星探测任务中使用的最大的降落伞 The biggest parachute we've ever used in a planetary mission.
它甚至无法使“好奇”号降到需要的速度 And that even doesn't slow Curiosity down enough,
因为火星的大气层太稀薄了 因此火箭将携带探测器 because Mars' atmosphere is quite thin, so then rockets carry
“好奇”号的视角
并引导探测器前住火星表面 the spacecraft and guide the spacecraft to the surface.
此时 我们无法决定它是成功登陆 There's nothing you can do at that point to ensure its success
还是会坠毁 or prevent its crashing...
但我们为这个结果投入了太多 ..and yet you've invested so much in the outcome.
我能做的只是蜷缩着身体 等待表示“好奇”号 All I could do was sort of curl up in a ball and wait for the
安全登陆火星的绿灯亮起 green light that Curiosity was safely on Mars.
耗费7年时间 和25亿美元的“好奇”号 Seven years and 2.5 billion in the making,
终于在2012年8月6日 Curiosity finally touched down
格林尼治标准时间6点32分成功着陆 at 6.32 Universal Time, on the 6th of August, 2012.
“好奇”号的视角
我坐在控制室 I was sitting in the control room watching the engineers,
看着监控“好奇”号信号的工程师们 who were actually monitoring the signals coming in from Curiosity,
他们在读收到的数据 and so they were reading out the data that they were getting
他们发现轮子已接触土壤 and they detected the wheels touching the soil.
几秒钟后 当电缆被切断 Then a few seconds went by when cables had to be cut
火箭喷气背包脱离 and the rocket jet pack had to fly away.
此时 他们才可以判断“好奇”号 And, only then, they understood that Curiosity was safe
已安全着陆 整个房间沸腾了 on the ground, and the whole room just erupted in celebration.
“好奇”号自着陆以来 已经对盖尔陨石坑 Since it landed, Curiosity has been exploring Gale Crater
进行了6年多的探索 for more than six years.
“好奇”号是一个流动的实验室 Curiosity is a roving laboratory.
我们通过挖取或者钻取样本 We actually collect samples by scooping it or by drilling,
或者仅仅是采集大气中的一些气体 or just by sucking in some of the atmospheric gas.
这些数据能帮助我们剖析 And it's that type of data that allows us to pick apart
事物背后的故事 the story that those things hold.
2015年 我们对火星物质的有机分子 In 2015, we made our first identification of organic molecules
进行了首次分析鉴定 that we think were coming from the Martian materials.
这对我们来说是一个转折点 And that is a turning point for us.
我们在那些岩石中发现了 What we found in those rocks
我们期望看到的天然有机物 is what we expected of natural organic matter.
这种物质在地球上也存在 It's what you would expect to find on Earth.
寻找有机物是寻找生命的线索 Finding the organic matter is the clue to searching for life.
大家都想知道火星是否出现过生命 What everybody wants to know is whether or not Mars
目前的答案是我们不知道 once had life, and the short answer is - we don't know.
从长远看 The somewhat longer answer is -
我们发现了可能支持生命存在的物质的痕迹 we see all the signs of materials that could have supported life.
我们有证据证明火星早期存在大量的水 We have evidence for lots of water early on.
我们发现了营养元素 我们发现了碳 我们发现了氧气 We see the nutrients, we see carbon, we see oxygen,
我们发现了氮 我们发现了磷 we see nitrogen, we see phosphorus,
我们看到了简单微生物 we see all the stuff that life needs
繁衍和生存所需的所有要素 in order to reproduce and survive as simple microorganisms.
在我看来 如果我们从未发现 For me personally, I find it might actually
火星上曾存在生命的证据 这其实更令人惊讶 be more surprising if we never found evidence of life on Mars.
我们的发现表明早期的火星 Everything we've found suggests that Mars was such a friendly,
适合生命存在 supportive place for life in its early history,
在其它恒星周围应该也存在很多这样的行星 and there should be a lot of planets like that around other stars,
宇宙中应该还存在大量生命 and lots of life in the universe.
因此如果我们无法找到其它生命 So, maybe we're getting to the point where it'll be more surprising
这会令人感到更加惊讶 if we never find other life.
因为有了“好奇”号的发现 最新的探测器 And so, thanks to Curiosity's discoveries, the latest wave
也许将最终回答这个问题 of spacecraft might finally answer the question -
火星是否曾存在生命 has there ever been life on Mars?
下集预告 Next time...
我们进入了气态巨行星的领域 ..we enter the realm of the gas giants...
去揭开这些最大和最古老的行星是如何 ..to discover how the largest and oldest of the planets
塑造整个太阳系的 sculpted the entire solar system.
朱庇特(木星） 众神之王 Jupiter, the godfather.
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