美國國家航空航天局「信使」號水星探測器發射升空 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 距離太陽2.3億公里
地球的鄰居火星是一顆寒冷貧瘠的岩石行星 Our planetary neighbour, Mars, is a cold, barren rock.
火星的表面 因為覆蓋著炙熱的沙土 呈現出銹紅色 Its rusted surface covered in parched sand.
但隱藏在沙塵之下的 But, beneath the dust,
一些痕跡說明火星曾存在生命 the planet bears the scars of a former life.
數十億年前 火星幾乎與地球無異 Billions of years ago, Mars was just like Earth.
那時 火星上厚厚的大氣層 A world with a thick atmosphere
為海洋的存在提供了保障 that supported oceans of water.
但如今 這個世界已不復存在 But, today, that world is gone.
火星已死 Mars lies dead,
而地球仍充滿生機 while the Earth thrives.
兩顆行星的命運如此不同的原因 仍然是不解之謎 Why the two planets had such different fates is a mystery
我們剛剛開始探索其中的奧妙 that we've only just begun to answer.
兩顆姐妹行星 地球與火星
火星
你們看到夜空中那個淡紅色的光點了嗎 You see that pale red point of light in the sky,
就在那邊 just there?
那就是火星 That's Mars.
通過小型望遠鏡觀察 它看起來幾乎和地球一樣 Through a small telescope, it appears almost Earth-like.
19世紀的天文學家 曾在地球的姐妹行星上 Our sister world - polar ice caps and dark surface
觀測到極地冰蓋和黑色的表面陰影 他們認為這是植被 markings that 19th-century astronomers thought were vegetation,
甚至是將極地融雪水引入乾旱的 even canals bringing meltwater down from the poles
赤道城市的河道 to arid equatorial cities.
赫伯特·喬治·威爾斯曾寫道 Across the depths of space,
在太空的深處有居民嫉妒地注視著我們 the inhabitants watched us "with envious eyes", wrote HG Wells.
我們現在知道火星上並沒有生命在注視我們 We now know that there are no eyes looking back at us.
火星是一個寒冷 乾旱的沙漠世界 Mars is a frozen, arid desert world.
但太空探測器的觀測結果表明 But a fleet of spacecraft have revealed
情況並非一直如此 that it hasn't always been that way.
「水手」4號探測器成功發射 Mariner 4 was successfully launched on time
「水手」4號探測器 1964年
開啟具有歷史意義的228天火星之旅 for its historic 228-day journey to Mars.
1965年7月15日 「水手」4號開始回傳照片 Picture information started to come in on July 15th, 1965.
首張火星表面清晰圖像
這個突破可與伽利略首次通過望遠鏡 A revelation comparable to Galileo's first view
觀測到月球相媲美 of the moon through a telescope.
「水手」4號短暫飛過火星上空 During its brief flyby,
首此為我們傳回了火星的近景照片 Mariner 4 gave us our first close-up glimpses of Mars.
「水手」9號探測器 1971年
當「水手」9號探測器進入環繞火星的軌道時 When Mariner 9 was placed into an orbit around Mars,
火星正被一場巨大的沙塵暴籠罩 it saw a planet blanketed by a gigantic dust storm.
在近一年的繞軌運行 In nearly a year of operation,
「水手」9號傳回了7000多張照片 they transmit more than 7,000 photographs.
「水手」9號在軌道上拍到了80%的火星表面 From orbit, Mariner 9 photographed 80% of the Martian surface.
維京計劃 1975年
首先 它有兩隻眼睛 可以拍攝到彩色的立體照片 First of all, there are two eyes, not only in colour but also
同時它還帶有紅外線光儲儀 in stereo, and in the infrared part of the spectrum.
它有觸覺和聽覺 It has a sense of touch, it has a sense of hearing,
但這台探測器最重要的特點是它的大腦 but by far the most important feature of the lander is its brain.
「維京」號探測器首次將我們帶到 The Viking programme took us down to the ground
火星表面 for the first time...
「維京」號在火星安全著陸
著陸 我們著陸了 Touchdown, we have touched down.
它揭示了一個 ..and revealed Mars...
完美著陸 Perfect set-down.
前所未見的火星 ..like never before.
這是傳回的第一條信息 There is the first piece of information coming in.
火星表面的首張彩色照片
利用過去50年收集的數據 我們可以繪製出 The data gathered over the last 50 years has allowed us to create
火星表面的詳細圖像 detailed maps of the Martian surface...
並嘗試拼湊出它的過去 ..and begin to piece together its past.
火星的地圖就像一本本故事書 Maps of Mars are like storybooks.
你可以讀到寫在火星表面的歷史 You can read the history of the planet
這是因為它基本沒有被腐蝕 written across its surface, and the reason for that is that there's
數十億年來 火星表面一直沒有被腐蝕 virtually no erosion, hasn't been for billions of years,
因此40億年前留下的痕跡 so the scars of events that happened even four billion years ago
依然清晰可見 can still be seen.
這種地圖被稱為地形高程圖 This is a type of map called an elevation map.
不同的顏色對應火星表面不同的高度 The colours correspond to difference in heights on the surface,
藍色表示高度較低 so blue means low
紅色或白色表示較高 and red and whites are high.
這個區域的高度大於火星其它區域的平均高度 Now, this region here, which is much higher on average than the rest
被稱為塔爾西斯 這裏被火山覆蓋 of Mars, is called Tharsis and it's covered in volcanoes,
包括太陽系最大的火山 奧林匹斯山 including the largest volcano in the solar system, Olympus Mons.
奧林匹斯山
塔爾西斯的另一側 是寬大延展的水手谷 At the other side of Tharsis is the great Valles Marineris,
在這個峽谷面前 地球上所有的峽谷 the Mariner Valley, and it is a canyon that dwarfs
都相形見絀 anything we see on Earth.
水手谷
火星的另一側是一個被稱為赫拉斯盆地的衝擊盆地 On the opposite side of the planet is an impact basin called Hellas.
赫拉斯盆地
從火山口邊緣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.
這意味著我們可以將珠穆朗瑪峰放在它的中間 That means you could fit Everest in the middle of there
還可以俯瞰珠穆朗瑪峰的頂峰 and look down on its summit.
盆地周圍的地區揭示了火星過去存在生命的跡象 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帶 遭受衝擊形成的 The Hellas basin is punched into the oldest-surviving terrain on Mars.
這片地形被稱為諾亞台地 It's called Noachis Terra
或諾亞之地 or The Land Of Noah.
這個名稱非常形象 因為它的表面是由流水 And that's a wonderfully evocative name because its surface is sculpted
雕蝕而成的 by flowing water.
諾亞台地
我們在最古老的火星表面發現了 All across the earliest Martian surface, we've glimpsed traces
湖泊和河流的痕跡 of what appear to have been lakes and rivers.
新一代的太空探測器被送往火星 And so a new generation of spacecraft has been sent to Mars,
美國國家航空航天局 「火星大氣與揮發物演化」探測器大氣分析
探索火星上是否存在水 to investigate the existence of water...
美國國家航空航天局 火星勘測軌道飛行器拍攝火星表面
這裏又發生過什麼 水會消失不見了 ..and what happened to the planet for it all to disappear.
這是史上最大膽的火星任務 Led by the most audacious Mars mission ever attempted...
我們在火星軌道附近遭遇了兩次衝擊 We have two-way Doppler and orbit around the planet Mars.
美國國家航空航天局「好奇」號火星探測器
將一噸重的探測器送到火星表面 ..to land a one-tonne rover on the Martian surface.
最後它經受了著名的「恐怖七分鐘」 Its final descent has become known as the "seven minutes of terror".
「好奇」號火星探測器成功登陸蓋爾撞擊坑 Curiosity touched down in Gale crater,
蓋爾撞擊坑的寬度為150公里 a 150-kilometre-wide impact basin,
科學家認為這裏曾存在一個古老的湖泊 thought to have been home to an ancient lake.
「好奇」號火星探測器耗資25億美元 是一個移動的化學實驗室 The rover is a 2.5 billion mobile chemistry lab...
它的任務是在火星表面提取樣本 ..designed to take samples of the Martian surface
並分析樣本成分 and analyse its composition.
「好奇」號在探索撞擊坑的同時 發現了被水流 As it explored the crater, Curiosity saw pebbles polished
磨光磨圓的鵝卵石 and rounded by running water
這裏曾是河水流經之地 in what had once been rivers and streams.
「好奇」號在著陸61天後 找到了理想的地點 Then, 61 days after landing, Curiosity identified the perfect
開始實施它的首要任務 spot to begin its primary mission.
撞擊坑裏有一塊名為「巖巢」的沙地 In a sandy area of the crater called the Rocknest,
探測器在這裏首次收集到了火星的土壤 the rover took its first scoops of Martian soil.
探測器對這些細沙進行化學分析 Chemical analysis of the fine, dusty sand revealed
並有了令人意外的發現 something quite unexpected.
儘管火星表面看起來完全乾燥 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」號發現的證據表明 Curiosity had found evidence of just how wet a planet
火星曾是一顆濕潤的行星 ancient Mars had been.
數十億年前 For hundreds of millions of years,
火星 40億年前
火星曾是一個水世界 Mars was a water world.
這裏雨水充沛 Rains fell,
河流奔騰 rivers ran,
而在北半球 and, in the northern hemisphere,
雨水匯聚成一個巨大海洋 water collected in a vast sea
覆蓋了火星表面的五分之一 that covered a fifth of the Martian surface.
這顆紅色行星曾經也呈現著藍色 The Red Planet was once blue.
所有證據表明 約40億年前 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,
當時的大氣壓力與地球目前情況相當 and the atmospheric pressure was at least that of Earth today,
甚至更高 perhaps even higher.
氣溫約為25攝氏度 在那個時候我也許完全可以 Temperatures were around 25 degrees, so I could have sat on Mars
坐到火星上 可能需要戴個呼吸面罩 all those years ago, admittedly with a mask to breathe,
因為那裏的氧氣很稀薄 但我可以坐在那裏 because there was very little oxygen, but I could have sat there
欣賞到這樣的風景 and looked out over a view like that.
所以我們不必只去想像火星曾經的樣子 So, you don't have to imagine what Mars was like in the past.
我們可以真切地體驗到 You can experience it.
就像現在這樣 It was pretty much like this.
但在後來的10億年間 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.
太陽系中 只剩下唯一一顆藍色的星球 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%被海洋覆蓋 70% of our planet's surface is covered by ocean.
成百萬的物種在海洋中繁衍生息 Under the waves, a million species thrive.
在陸地上 雨水維繫著地球微妙的生態系統 While on land, the rains support Earth's delicate ecosystems...
為大量的生命提供家園和庇護 ..providing a home for an abundance of life.
但它並非一直如此 But it hasn't always been this way.
地球 40億年前
早期的地球與我們今天所知的地球不同 The early Earth was unrecognisable from the planet we know today.
早期地球大氣中的二氧化碳濃度很高 Its atmosphere thick with carbon dioxide.
地球上的海水呈酸性 And its oceans acidic.
40億年前 地球曾是一個有毒的混亂世界 Four billions years ago, Earth was a troubled, toxic world...
而當時的火星正在蓬勃發展 ..while Mars was flourishing.
但兩顆行星都將被太空的 But both planets were about to be engulfed
一場大災難吞沒 by a cataclysm from space.
為了瞭解當時的情形 To understand what happened,
我們必須將眼光投向地球以外的地方 we have to look beyond our own world.
僅觀察地球表面 是無法去解讀 You can't read the deep history of the Earth by looking
其久遠歷史的 因為地球的地質活動頻繁 at its surface because our planet is a geologically active world.
由於火山活動 風化作用和海洋的作用 The surface is constantly being reshaped by volcanic activity,
地球表面不斷地發生變化 但我們有一位同伴 weathering, and the actions of the oceans, but we have a companion,
那就是月球 數十億年來 月球一直不活躍 the moon, which has been inactive for many billions of years,
因此太陽系在這個區域發生的一切 and so the history of events that happened in this region
都被記錄在了月球的表面 of the solar system is written all over its surface.
遍佈隕石坑是月球表面最顯著的特點 The most distinctive feature of the moon's surface
月球表面記錄下了所有來自太空的撞擊 are its craters - it is literally covered in a record of impacts
我們可以據此分析月球不同部分的 from space, and that allows us to estimate the relative ages
相對年代 of different parts of the moon.
很簡單 Quite simply, if there are more craters,
隕石坑更多的區域一定更古老 then that piece of the moon must be older.
這說明它被撞擊的次數更多 There's been more time for the impacts to build up.
但除了判斷相對年代 我們還可以做得更多 But we can do better than just measure the relative ages
因為我們還有岩石 阿波羅號宇航員 because we have rocks, the moon rocks brought back
帶回來的月球岩石 by the Apollo astronauts.
我們可以分析岩石內部放射性元素的衰變速度 We can estimate the ages of rocks very precisely by looking
非常準確地判斷岩石的年齡 at the rates of decay of radioactive elements inside them.
它們就像小小的秒錶 從岩石形成的那一刻 They're like little stopwatches that start ticking the moment
開始滴答作響 這些都是太空撞擊帶來的 the rocks are formed, in this case by the impacts from space.
因此我們可以將某個月球區域的 So, the moon rocks allow us to tie the number of craters
隕石坑數量 in a particular region of the moon
和岩石的絕對年齡聯繫起來分析 to an absolute age measured by the rocks.
這不僅能幫助我們確定月球表面受到撞擊的時間 And this doesn't just allow us to date impacts on the lunar surface.
毛德隕石坑
哈德利隕石坑
我們還能通過隕石坑 It means that craters can be used
分析太陽系的演化歷史 to read the histories of worlds across the solar system.
涅庫姆隕石坑
也包括火星的歷史 Including Mars.
當我們將所有數據集中在一起 我們有了驚人的發現 When we gathered all the data, we discovered something surprising.
約38億到39億年前 隕石坑形成的速度 There was a peak in the crater formation rate, about 3.8
達到峰值 to 3.9 billion years ago,
這表明整個太陽系內在這個時期出現了劇烈的天體撞擊 which signified a period of intense violence in the solar system,
這被稱為晚期重大撞擊事件 and that is called the Late Heavy Bombardment.
火星 39億年前
無數小行星衝進火星的大氣層燃燒解體 Countless asteroids fragmented in Mars' atmosphere,
給整個火星帶來了一場浩劫 raining havoc across the planet.
據估計 在火星表面 It's estimated that 53 tonnes of rock
每平方米有53噸岩石落下 fell on every square metre of Mars.
超過三分之一的火星表面傷痕纍纍 Over a third of the planet's surface was obliterated...
火星被推到了死亡的邊緣 ..and Mars was pushed to the brink of death.
月球表面的證據告訴我們太空曾發生 Whilst the evidence from the surface of the moon tells us
晚期重大撞擊事件 但並未揭示其中的原因 that the Late Heavy Bombardment happened, it doesn't tell us why.
為此 我們需要通過計算機模型 For that, we have to resort to computer models of the evolution
來還原太陽系的演化過程 在研究中 of the solar system, and, when we do that,
我們發現根源來自海王星 they point the finger at Neptune.
人們認為海王星在向外遷移時經過了柯伊伯帶 It's thought that Neptune migrated outwards into the Kuiper belt...
無數冰質岩石天體集中在這裏 ..a region of icy, rocky objects
運行於太陽系的邊緣地區 orbiting at the edge of the solar system.
天體間由此產生的相互引力破壞了這些軌道 The resulting gravitational interactions disrupted those orbits
並將很多天體推向太陽系的內部 and sent many of the objects inwards to the inner solar system,
這很可能導致了晚期重大撞擊事件的發生 and that may have been the cause of the Late Heavy Bombardment.
地球 39億年前
地球當時也遭受了猛烈的撞擊 Earth also suffered the onslaught,
在此後的數千萬年裏 and, for tens of millions of years,
這兩顆姐妹行星的命運一直懸而未決 the fortunes of the two sister worlds hung in the balance.
但就在這種最不樂觀的條件下 But, just when conditions appeared at their least promising,
地球最重要的特徵出現了 Earth's most precious characteristic emerged.
生命 Life.
有充足的證據表明 約38億年前 There is good evidence that life was present on Earth
地球就已出現生命 我認為可以排除 around 3.8 billion years ago, and discounting the - I think -
那種最小的可能性 就是生命起源於 remote possibility that life began elsewhere
太陽系的其它地方 又被隕石或彗星 in the solar system and was transported to the Earth
帶到地球的說法 on meteorites or comets,
那麼可以說生命一定是從地球開始的 that means that life must have begun here.
在這顆行星的某個地方產生了 So, somewhere on this planet there was a transition
由地球自身的化學變化 from geochemistry - the chemistry of Earth,
轉變為了生物化學的演變 to biochemistry - the chemistry of life.
但這樣的轉變到底是如何產生的 And whilst the precise details of how that transition occurred
至今仍是個迷 人們認為溫暖的火山池 remain a mystery, it's thought that in warm volcanic pools
或深海熱泉口最適宜構成 or deep sea hydrothermal vents, conditions were right
生命的基本化學單位自發形成 for the chemical building blocks of life to form spontaneously.
這意味著 如果太陽系的其它地方 And that means that if similar conditions
也存在相似的條件 were to be found elsewhere in the solar system,
就也有可能誕生生命 it might be possible that life began there too.
阿特拉斯-5運載火箭點火升空 Ignition, and lift off of the Atlas V rocket with MRO.
火星勘測軌道飛行器
火星勘測軌道飛行器發射成功 Surveying for the deepest insights
開始深入探索火星的神秘演變 into the mysterious evolution of Mars.
2005年 美國國家航空航天局開始了 So, in 2005, NASA embarked on a mission to look
在火星尋找相同環境的任務 for those same environments on Mars.
火星 現在
10多年來 火星勘測軌道飛行器 For more than a decade, the Mars Reconnaissance Orbiter
一直在關注這顆紅色星球 has been our eyes on the Red Planet...
美國國家航空航天局 火星勘測軌道飛行器
它傳回的數據 ..sending back more data
它傳回的數據遠多於其它火星任務傳回的數據之和 than all the other Mars missions combined.
火星勘測軌道飛行器拍攝了6萬多張圖片 MRO has made more than 60,000 orbits,
覆蓋了99%以上的火星表面 mapping over 99% of the planet's surface.
它的高分辨率攝像機揭示了一個前所未有的火星 Its high-resolution cameras have revealed Mars as never before,
人們發現了極地雪崩 discovering polar avalanches,
以及流動的沙丘 shifting sand dunes...
還有沙漠 甚至液態雪融水的季節性流動 ..and what could be seasonal flows of sand or even liquid meltwater.
2017年 火星勘測軌道飛行器開始關注 Then, in 2017, MRO turned its gaze
紅色星球最古老的特徵之一 to one of the Red Planet's oldest features,
波江盆地 the Eridania Basin.
波江盆地 38億年前
38億年前 這個盆地還是一片汪洋 3.8 billion years ago, the basin was a vast sea...
這裏的水容量 ..holding ten times more water
是北美五大湖區水容量的10倍 than the Great Lakes of North America.
火星勘測軌道飛行器在這裏發現了找尋已久的證據 And it was here that MRO found the evidence it was looking for.
400米厚的礦物沉積 這通常形成於 400-metre-thick deposits of minerals that, on Earth,
地球的深海熱泉口 form in deep sea hydrothermal vents.
在波江盆地 火星勘測軌道飛行器發現 In the Eridania Basin, MRO revealed that conditions on Mars
火星出現過適合孕育生命的條件 had once been ripe for the emergence of life.
我們無法確切知道火星上是否出現過生命 或這些生命是否仍然存在 We won't know for sure whether life began or even perhaps still exists
除非前往火星並找到實物證據 on Mars until we go there and find physical evidence -
微生物或許就深埋於液態水綠洲的土壤之中 so, microbes buried deep below the soil in oases of liquid water,
或者會存在微生物化石 但我們知道 or maybe microbe fossils - but what we do know is that,
35億年前 地球開始出現生命時 when life began here on Earth, 3.8 billion years ago,
火星的條件與地球非常相似 the conditions on Mars were very similar.
火星上也有海洋 有火山活動 There were seas, there was volcanic activity,
甚至火星上的海底也存在深海熱泉 there were even hydrothermal vent systems on the floors of its oceans.
至少有可能的是 地球並不是太陽系 So, it is at least possible that Earth is not the only world
唯一有生命開始的星球 in the solar system where life began.
火星在諾亞時代 The habitable conditions during what's known
出現的宜居條件持續了數億年 as Mars' Noachian era persisted for hundreds of millions of years.
但紅色星球的生命發展前景突然改變 But then, prospects for life on the Red Planet changed dramatically.
在大約35億年前 諾亞時代結束 Around 3.5 billion years ago, the Noachian era drew to a close
火星進入了更寒冷和乾旱的時期 即赫斯伯利亞紀時期 and Mars entered a more frozen, arid phase, known as the Hesperian.
曾經在諾亞時代 在火星表面自由流動的水 The water that flowed freely over the surface during the age of Noah
被封鎖在了巨大的冰庫裏 became locked away in giant reservoirs of ice.
但是就在這個時期 火星的火山活動更加活躍 But, around the same time, Mars became more volcanically active,
火山爆發和地下熔岩流 and the volcanic eruptions and sub-surface lava flows
偶爾會融化冰層 導致災難性的洪水 occasionally melted the ice, leading to catastrophic flooding.
這一定是太陽系中 They must have been some of the most spectacular sights
當時最為壯觀的景象 in the history of the solar system.
火星 35億年前
當熔岩向上推動地殼 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.
洪水從南部的高地肆虐而下 It raged down from the southern highlands...
一直來到一個被稱為艾徹斯深谷的地方 ..until, in a place known as Echus Casma, it plunged
它從4000米高的懸崖俯衝而下 over cliffs 4km high...
這形成了太陽系史上 ..creating the largest waterfall
最大的瀑布 the solar system has ever seen.
艾徹斯深谷絕不同於地球上的任何瀑布 Echus Casma would have been like no waterfall ever seen on Earth.
35萬立方公里的水流過這裏 350 cubic kilometres of water flowed over it.
就像一個長寬高均為70公里的立方體 That's like a cube 70km by 70km by 70km.
所有的水流到寬10公里 It all entered into a canyon 10km wide
長100公里的山谷裏 而這一切就發生在幾周內 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蝕的痕跡 ..leaving the evidence of the falls etched into the face of the planet.
艾徹斯深谷
我們不知道火星為何會從溫暖潮濕的氣候 We don't know precisely why the climate of Mars changed
轉變成寒冷乾旱的氣候 from warm and wet to cold and arid.
我們討論的是35億年前 We're talking about events that happened
發生在數億公里外的一顆行星上的事件 three and a half billion years ago on a planet hundreds of millions
這是一個很難的課題 of kilometres away, so it is a hard problem.
但我們強烈懷疑 火星表面 But we do strongly suspect that changes happening
之所以會發生變化 on the planet's surface were driven
至少有一部分原因來自於火星內部的變化 at least in part by changes in the planet's interior.
火星的核心深處發生的一些變化 Deep within Mars' core,
很可能導致了這顆行星的死亡 something was causing the planet to die...
我們可以從火星的大氣層中找到證據 ..and the evidence can be found in Mars' atmosphere.
倒計時 10 9 8 7 6 T-minus ten, nine, eight, seven, six,
5 4 3 five, four, three,
火星大氣與揮發物演化任務
2 1 two, one.
主發動機開始啟動 點火 搭載「火星大氣與揮發物演化」探測器的 Main engine start, ignition, and lift-off
阿特拉斯-5型運載火箭發射 of the Atlas V with MAVEN,
執行任務 在火星的大氣層 looking for clues about the evolution of Mars
尋找火星演變的線索 through its atmosphere.
2014年9月 美國國家航空航天局的「火星大氣與揮發物演化」探測器 In September 2014, NASA'S MAVEN probe made its final
最後一次靠近火星 approach to the Red Planet.
它的任務是調查火星 Its mission - to understand what drove the planet's
氣候變化的原因 dramatic climate change.
「火星大氣與揮發物演化」探測器配備有一系列儀器 MAVEN is equipped with an array of instruments designed to measure
可分析火星大氣中原子和分子的變化 the behaviour of the atoms and molecules in Mars' atmosphere.
探測器沿著一個橢圓軌道繞火星飛行 The spacecraft circles Mars in an elliptical orbit...
它的任務是全面瞭解 ..allowing it to measure the full profile
火星外層大氣的狀況 of the planet's upper atmosphere.
它的最低點 At its lowest point,
距離火星表面僅150公里 it's just 150km above the surface.
最高點則會超過6000公里 At its highest, a little over 6,000 kilometres.
「火星大氣與揮發物演化」探測器在火星大氣層的最頂端 And it was at the very top of Mars' atmosphere that MAVEN found
發現了火星發生變化的原因 the key to the mystery of what happened to Mars.
詳細的測量分析表明 Detailed measurements revealed gas is being lost
火星大氣中的氣體正在消失 from the Martian atmosphere,
以大約 escaping to space
每秒兩千克的速度散失到太空中 at a rate of about two kilograms every second.
人們認為在漫長的時間裏 火星大氣的逐漸散失 Over time, it's thought this gradual stripping away of Mars' atmosphere
致使圍繞火星的絕緣層慢慢變薄 has slowly thinned the insulating layer surrounding the planet...
最終導致了火星表面溫度的急劇下降 ..causing surface temperatures to plummet.
然而是什麼原因導致火星大氣消失 But what was it that caused Mars to lose its atmosphere
而地球的大氣會穩定存在呢 while Earth clung on to hers?
在距離這裏1.5億公里的地方 就是我們看到的落日 150 million kilometres away in that direction is the setting sun,
這是一個巨大的核聚變反應堆 a giant nuclear fusion reactor.
可容納100萬個地球 You can fit one million Earths inside it.
它的表面溫度 Now, the surface temperature
約為6000攝氏度 is only around 6,000 degrees Celsius,
但太陽大氣 也就是日冕的溫度 but the sun's atmosphere, known as its corona,
可達100萬攝氏度 is at one million degrees.
這意味著它以所謂的等離子體形式存在 And that means it's in the form of what's known as a plasma, a soup
一種帶電粒子的混合物 of electrically charged particles.
如今一些粒子快速移動 以太陽風的形式 Some of those particles are moving around so fast that they can escape,
從太陽表面逃逸 and they stream away in what's known as the solar wind.
它們會以每秒幾百公里的驚人速度到達地球 They reach the Earth travelling at a few hundred kilometres per second.
如果不加以保護 它們就會吹走我們的大氣 And, if we weren't protected, they would strip away our atmosphere.
當太陽落到地平線以下時 And when the sun dips below the horizon...
具備保護性的力場有時會在夜空中出現 ..there are times when that protective force field is revealed.
看那邊 Just look at that!
那就是美麗的極光 I mean, there is the aurora.
這是大自然的傑作 它們呈現於天空之上 It's the laws of nature, all of them, written across the sky.
來自恆星內部核聚變反應堆的帶電粒子 Electrically-charged particles have been driven away from the sun,
從太陽的表面逃逸 ultimately from nuclear fusion reactions in the core of a star.
它們穿過太陽系 撞擊地球磁場 They're crossing the solar system, hitting the Earth's magnetic field,
將地球磁場延伸至地球的陰暗面 stretching it out on the dark side of the planet.
然後磁場像橡皮筋一樣彈回來 The field then snaps back like an elastic band,
使所有帶電粒子沿著兩極的磁場線 accelerating all of those charged particles up and down
上下加速 就在這裏 在冰島的上空 the field lines to the poles, which is here in the skies
當帶電粒子撞擊大氣中的 over Iceland, and they hit nitrogen
氮氣和氧原子時 and oxygen molecules in the atmosphere.
你將看到量子力學的產生 它們使原子興奮 And you're seeing quantum mechanics - they're exciting the
使原子發出帶有特殊顏色的光 molecules so that they emit light in characteristic colours.
這是我們看到地球磁場的 And, if you think about it, this is the only time
唯一機會 that we really see the Earth's magnetic field.
這是地球生命 It's one of the reasons why life on Earth
得以延續40億年的原因之一 has been able to persist for four billion years.
所以在某種意義上 這也是我們存在的原因 In a sense, that's the reason that you exist.
地球磁場保護了地球大氣 It's Earth's magnetic field that protects our atmosphere
不被太陽風破壞 from the ravages of the solar wind,
這種保護盾的形成 and that protective shield has its origins deep
起源於地球的內部深處 in the planet's interior.
在我的腳下幾千公里的地方 Thousands of kilometres down below my feet,
你的腳下也是一樣 就是地球的外地核 actually below your feet now, is the Earth's outer core,
它是一團沸騰的鐵水 which is a seething mass of molten iron.
內部產生的對流能使鐵水上升 Convection currents cause the molten iron to rise,
而地球自轉使鐵水也會跟著旋轉 and then the Earth's rotation causes it to spiral around.
此時導電液體的螺旋流動 Now, a spiralling, circling flow
就像一台發電機 of an electrically conducting liquid is a dynamo.
這台發電機能夠產生磁場 地球磁場不僅能上升到 A dynamo generates a magnetic field and the Earth's field rises up,
地球表面 同時也存在於外太空 not just to the surface here, but out into space,
對地球形成了保護盾 forming our protective shield.
也就是我們看到的這一切 And that is what you see there.
和地球一樣 And just like Earth,
古老的火星也曾擁有隔離太陽的保護盾 ancient Mars was also shielded from the sun.
極光曾在火星的兩極跳躍 Aurora once danced above its poles...
保護火星的大氣和大氣之下的海洋 ..keeping guard over the Martian atmosphere and seas below.
但在35億到40億年前 But between 3.5 and 4 billion years ago,
火星的發電機關閉了 Mars' dynamo switched off.
隨著磁場的減弱 兩極附近的極光 The aurora surrounding the poles slowly faded away
慢慢消失 as the magnetic field diminished...
於是火星大氣開始被太陽風 ..allowing the atmosphere to be stripped away
吹離 by the solar wind.
失去保護的海洋蒸發 地表結冰 Without protection, seas evaporated, the surface froze,
火星的地貌完全改變 and Mars was transformed.
地球 35億年前
與此同時 火星的姐妹行星的命運 At the same time, the fortunes of Mars' sister world
即將發生截然不同的變化 were about to take a very different turn.
在接下來的10億年裏 For the next billion years or so, Earth was indistinguishable
地球和火星的早期地貌沒有區別 from those landscapes of early Mars-
即一片被海洋包圍的貧瘠大陸 barren continents surrounded by ocean.
但在地球的海洋中 生命開始改變地球 But in Earth's oceans, life was beginning to transform the planet.
原始海藻開始中和海洋的酸度 Primitive algae started to neutralise the ocean's acidity
並且用氧氣替代紅色濃霧 and replace the dense red fog of Earth's methane-rich
即富含甲烷的地球大氣 atmosphere with oxygen.
約6億年前 富含氧氣的大氣使複雜的生命 Around 600 million years ago, that oxygen-rich atmosphere allowed
得以在海洋進化 在陸地繁衍生息 complex life to evolve in the oceans, colonise the land,
並最終產生了如今這個充滿生機的世界 and ultimately produce this almost-infinitely rich living world
而我們正是這個世界的一部分 today, of which we are a part.
火星死去 但地球欣欣向榮 While Mars died, Earth flourished.
為瞭解兩顆姐妹行星為何命運如此不同的原因 To understand why the two sisters had such different destinies,
我們必須回到 you have to go right back
兩顆行星的形成之初 to the time the planets were forming.
太陽系 45億年前
在火星和地球誕生時 When Mars and Earth were born,
太陽系還是由氣體和岩石組成的混沌漩渦 the solar system was a chaotic vortex of gas and rock.
物質聚集在一起 逐漸變大 然後又會被撞碎 Material clumped together and grew, only to be smashed apart.
隨著時間的推移 有些物體變得足夠大 Over time, some of the objects became large enough to survive
可以承受較小的撞擊 並繼續變大 at least the smaller impacts, and continued to grow,
這包括胚胎期的地球和火星 including the embryonic planets Earth and Mars.
但兩顆行星有一個重要的不同 But there was one crucial difference between the young planets.
火星形成於太陽系中 Mars formed in a region of the solar system
岩石物質相對較少的區域 with considerably less rocky material.
這對行星的生長產生了深遠的影響 And that had a profound impact on the planet's growth.
相對來說 火星要小很多 它的直徑約為地球的一半 Mars is a significantly smaller world - it's about half the diameter
這也是兩顆行星產生差異的原因 of the Earth, and that makes all the difference.
儘管我們並沒有完全瞭解其中的細節 Although the details are not yet fully understood,
但可以明確的是 由於火星體積更小 導致它的發電機 it seems clear that Mars' smaller size meant that its dynamo switched
在數十億年前關閉了 off many billions of years ago.
體積更小意味著火星的核心比地球的核心冷卻得更快 Being smaller meant Mars' core cooled more quickly than Earth's.
這顯然也是火星失去磁場的 And this is certainly part of the reason why Mars
原因之一 lost its magnetic field.
儘管火星與太陽的距離大於地球與太陽的距離 Even though the planet is further away from the sun than we are,
但太陽風帶走了它的大氣 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,
二者在太陽系的位置和大小導致了 the difference in position and size in the solar system
它們完全不同的命運 led to very different fates.
很久以前 兩顆姐妹行星誕生 Long ago, two sister worlds were born.
童年時期的火星溫暖濕潤 In childhood, Mars was warm and wet...
而地球荒涼且充滿毒氣 ..whilst the Earth was inhospitable and toxic.
兩顆年輕的行星都在晚期重大撞擊事件中 Both young planets survived the violence
活了下來 of the Late Heavy Bombardment,
並成為成熟的行星 emerging as mature worlds,
具備了生命所需的所有要素 primed with all the ingredients for life.
但那顆小一些的行星的核心深處正在消亡 But deep inside, the smaller of the two was dying.
火星的海洋乾涸 Mars' seas dried up.
隨著火星內部的冷卻 它的火焰也接連熄滅 And as the planet's interior cooled, one by one her fires went out.
奧林匹斯山是太陽系最大的火山 Olympus Mons, the largest volcano in the solar system,
它的最後一次噴發是在大約2500萬年前 last erupted around 25 million years ago.
隨著熔岩變成岩石 As the lava turned to stone,
火星被時間凍結 Mars was frozen in time.
因此 直至今日 它的表面依然滿目瘡痍 佈滿沙塵 And so, today, her surface lies rusted and gathering dust.
但這也許並不是火星故事的結局 But that might not be the end of Mars' story.
因為下一代太空探測器正在行動 Because the next generation of spacecraft are already on their way.
美國國家航空航天局獵戶座飛船
美國國家航空航天局的獵戶座飛船目前正在進行高級測試 NASA Orion - currently in advanced testing.
可搭載4名宇航員
比以往任何時候更深入太空
歐洲太空局「火星生命」
歐洲太空局的 ESA ExoMars -
「火星生命」探測聯合任務旨在尋找火星的生命跡象 a fleet of spacecraft designed to search for signs of life.
這是有史以來最具野心的私人太空計劃 And the most ambitious private space mission ever conceived.
美國太空探索技術公司 重型獵鷹火箭
世界上最強大的火箭
科學家研發出可將人類送往火星表面的運載火箭 A launch vehicle developed to take humans to the surface of Mars.
火星在某種意義上是一個失敗的世界 Mars is, in a sense, a failed world,
它是一抹褪色的餘燼 上面鐫刻著代表火星迷人過去的記憶 a faded ember etched with the memories of a more enticing past,
但火星上曾經有過 也許仍有生命存在 but there may have been, and may still be, life on Mars.
同時 在太陽系發現第二種生命形式 And the discovery of a second genesis in our solar system
將產生深遠的哲學 科學和文化影響 would have profound philosophical, scientific and cultural consequences
因為這意味著生命起源 because it would mean there is a sense of inevitability
存在必然性 about the origin of life,
這意味著宇宙中 and that would mean that the universe
可能會充滿生命 我們並不孤單 is most likely teeming with life - that we are not alone.
但我認為同樣重要的是 像火星這樣歷史久遠的行星 But equally importantly, I think, is the role that a planet
在未來可能發揮的作用 with a history like Mars could play in our future.
火星上資源豐富 它的地下蘊藏著 Mars is rich in resources, it has vast reservoirs of frozen
豐富的冰凍水 還有礦物質 water below the surface, and minerals -
像鐵 氮 碳 氧 這些都是 iron, nitrogen, carbon, oxygen - all the things
文明發展所需的要素 you need to support a civilisation.
因此我認為 在我有生之年 And that's why I think that, in my lifetime,
將出現火星人 火星人就是我們 there will be Martians, but the Martians will be us.
我們將前住火星定居 We will go to Mars and make it our home,
這顆古老的紅色星球將成為我們人類走出地球 and that old red world will become our first step
實現星際漫遊的第一步 beyond the cradle, and out to the stars.
《行星》幕後故事
火星確實激發了 Mars really captures
詹妮弗·艾根博德博士 美國國家航空航天局戈達德太空飛行中心
我們的想像力 our imagination,
部分原因是它離地球很近 partly because it's so close.
我認為人類對火星非常感興趣 是因為 I think people are really interested in Mars because it actually
約翰·格勒青格教授 加州理工學院
它與地球很相似 is so similar to Earth.
火星離地球很近 我們可以帶著機器人和飛行任務 It's close by, it's easy to travel there with robots
前往火星 事實上我們已經進行過很多探索 and space missions, and so we've done a lot of exploration.
每次前往火星都會有新的發現 And, every time you go and look, you discover something new.
美國國家航空航天局於2011年11月26日發射「好奇」號火星探測器 NASA Curiosity launched on the 26th of November, 2011.
但科學家面臨的最大難題 But the biggest obstacle facing the mission team
不是如何離開地球 wasn't leaving the Earth.
與我們通過太空探測器前往的其它地方相比 Mars has a unique set of challenges
火星給我們帶來一系列獨特的挑戰 compared to other places we go with spacecraft.
阿什溫·瓦薩瓦達博士 美國國家航空航天局噴氣推進實驗室
火星有大氣層 但它很稀薄 不足以 Mars has an atmosphere but it's thin, so it's not enough
讓我們的速度慢下來 to really slow you down,
但在我們試圖著陸時又足以讓我們燃燒起來 but it is enough to actually burn you up as you're trying to land.
「好奇」號以每小時兩萬公里的速度 Curiosity reached the top of the Martian atmosphere,
抵達火星大氣層的邊緣 travelling at 20,000km per hour.
「好奇」號是一個巨大的探測器 它重達一噸 Curiosity is a big rover. It weighs a metric ton,
因此要讓它成功著陸 and so landing that required every trick in the book
我們必須從以往的任務中學習著陸火星的所有技巧 of how we've learned to land on Mars with previous missions.
為了安全著陸 「好奇」號必須將速度減到 To land safely, the rover had to be slowed
每小時4000公里以下 to less than 4km per hour.
航天器到達火星時的速度很快 You end up arriving at Mars going really fast,
因此必須減速 so you actually have to slow down,
我們通過一個防熱罩實現減速的目的 and we do that using a heat shield,
航天器會燃燒很多燃料 產生大量熱量 which burns off a lot of energy and creates a lot of heat,
因此我們必須吸收這些熱量 防止損壞航天器 so you have to absorb that somehow and not damage the spacecraft.
接下來 降落傘登場 Then a parachute comes out.
這是我們在行星探測任務中使用的最大的降落傘 The biggest parachute we've ever used in a planetary mission.
它甚至無法使「好奇」號降到需要的速度 And that even doesn't slow Curiosity down enough,
因為火星的大氣層太稀薄了 因此火箭將攜帶探測器 because Mars' atmosphere is quite thin, so then rockets carry
「好奇」號的視角
並引導探測器前住火星表面 the spacecraft and guide the spacecraft to the surface.
此時 我們無法決定它是成功登陸 There's nothing you can do at that point to ensure its success
還是會墜毀 or prevent its crashing...
但我們為這個結果投入了太多 ..and yet you've invested so much in the outcome.
我能做的只是蜷縮著身體 等待表示「好奇」號 All I could do was sort of curl up in a ball and wait for the
安全登陸火星的綠燈亮起 green light that Curiosity was safely on Mars.
耗費7年時間 和25億美元的「好奇」號 Seven years and 2.5 billion in the making,
終於在2012年8月6日 Curiosity finally touched down
格林尼治標準時間6點32分成功著陸 at 6.32 Universal Time, on the 6th of August, 2012.
「好奇」號的視角
我坐在控制室 I was sitting in the control room watching the engineers,
看著監控「好奇」號信號的工程師們 who were actually monitoring the signals coming in from Curiosity,
他們在讀收到的數據 and so they were reading out the data that they were getting
他們發現輪子已接觸土壤 and they detected the wheels touching the soil.
幾秒鐘後 當電纜被切斷 Then a few seconds went by when cables had to be cut
火箭噴氣背包脫離 and the rocket jet pack had to fly away.
此時 他們才可以判斷「好奇」號 And, only then, they understood that Curiosity was safe
已安全著陸 整個房間沸騰了 on the ground, and the whole room just erupted in celebration.
「好奇」號自著陸以來 已經對蓋爾隕石坑 Since it landed, Curiosity has been exploring Gale Crater
進行了6年多的探索 for more than six years.
「好奇」號是一個流動的實驗室 Curiosity is a roving laboratory.
我們通過挖取或者鑽取樣本 We actually collect samples by scooping it or by drilling,
或者僅僅是採集大氣中的一些氣體 or just by sucking in some of the atmospheric gas.
這些數據能幫助我們剖析 And it's that type of data that allows us to pick apart
事物背後的故事 the story that those things hold.
2015年 我們對火星物質的有機分子 In 2015, we made our first identification of organic molecules
進行了首次分析鑒定 that we think were coming from the Martian materials.
這對我們來說是一個轉折點 And that is a turning point for us.
我們在那些岩石中發現了 What we found in those rocks
我們期望看到的天然有機物 is what we expected of natural organic matter.
這種物質在地球上也存在 It's what you would expect to find on Earth.
尋找有機物是尋找生命的線索 Finding the organic matter is the clue to searching for life.
大家都想知道火星是否出現過生命 What everybody wants to know is whether or not Mars
目前的答案是我們不知道 once had life, and the short answer is - we don't know.
從長遠看 The somewhat longer answer is -
我們發現了可能支持生命存在的物質的痕跡 we see all the signs of materials that could have supported life.
我們有證據證明火星早期存在大量的水 We have evidence for lots of water early on.
我們發現了營養元素 我們發現了碳 我們發現了氧氣 We see the nutrients, we see carbon, we see oxygen,
我們發現了氮 我們發現了磷 we see nitrogen, we see phosphorus,
我們看到了簡單微生物 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.
在我看來 如果我們從未發現 For me personally, I find it might actually
火星上曾存在生命的證據 這其實更令人驚訝 be more surprising if we never found evidence of life on Mars.
我們的發現表明早期的火星 Everything we've found suggests that Mars was such a friendly,
適合生命存在 supportive place for life in its early history,
在其它恆星周圍應該也存在很多這樣的行星 and there should be a lot of planets like that around other stars,
宇宙中應該還存在大量生命 and lots of life in the universe.
因此如果我們無法找到其它生命 So, maybe we're getting to the point where it'll be more surprising
這會令人感到更加驚訝 if we never find other life.
因為有了「好奇」號的發現 最新的探測器 And so, thanks to Curiosity's discoveries, the latest wave
也許將最終回答這個問題 of spacecraft might finally answer the question -
火星是否曾存在生命 has there ever been life on Mars?
下集預告 Next time...
我們進入了氣態巨行星的領域 ..we enter the realm of the gas giants...
去揭開這些最大和最古老的行星是如何 ..to discover how the largest and oldest of the planets
塑造整個太陽系的 sculpted the entire solar system.
朱庇特(木星） 眾神之王 Jupiter, the godfather.
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