如果,地球獨一無二 What if Earth were unique

2020-12-18 英語東

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If we just take the time to observe it, nature provides us with a fascinating spectacle. Over time, the inhabitants of our planet have woven complex relationships of collaboration, symbiosis, dependence and predation.

如果我們花時間去觀察大自然,會發現它為我們展現了迷人的奇觀。隨著時間的推移,我們星球上的居民編織了協作、共生、依賴和掠奪的複雜關係。

Earth is the planet of life. Running, crawling or flying, life abounds everywhere.

地球是一個滿是生命的星球。奔跑著的、爬行著的或飛翔著的,到處都是生命。

But for all this beautiful diversity to have proliferated, Earth has had to provide a favourable environment for around four billion years. What, then, were the conditions which enabled the blooming of life on Earth?

但是,為了讓這些美麗的多樣性得以增殖,地球必須在大約40億年的時間裡一直為它們提供一個有利的環境。那麼,使地球上生命繁盛的條件是什麼呢?

And could these conditions be present elsewhere, resulting in alternative ecosystems? In an attempt to answer these questions, scientists scour the cosmos for signs of life.

這些條件會不會出現在其他地方,導致一種另類的生態系統呢?為了回答這些問題,科學家在宇宙中尋找著生命的跡象。

They've built giant telescopes with which to probe the universe and listen to the whispering of the stars. But space has remained resolutely silent.

他們建造了巨大的望遠鏡,用它來探測宇宙,聆聽星星的低語。但太空一直堅決地保持著沉默。

Scientists have sent probes to the very edges of our Solar System. But all they have sent back have been images of planets inimical to life.

科學家們已經向太陽系的邊緣發射了探測器。但他們發回的都是與對生命有害的行星的圖像。

Over the last 25 years, however, astronomers have discovered thousands of incredibly diverse planets, in our galaxy alone. So many strange worlds, with no sign of life.

然而,在過去的25年裡,天文學家僅在我們的星系中就發現了成千上萬種不同的行星。有那麼多奇怪的世界,卻沒有生命的跡象。

Not one other planet similar to our own. So could it be that Earth really is unique?

沒有任何一個星球與我們的地球相似。所以地球真的是獨一無二的嗎?

In this programme, scientists will tell the fascinating story of how Earth developed, how this ball of ice and dust became the planet of life. In their laboratories or out on the ground, they continue their research into the extraordinary circumstances which allowed life to appear and eventually transform this planet.

在本期節目中,科學家將講述有關地球如何發展的迷人故事,即這個由冰和塵埃組成的球體是如何成為一顆具有生命的星球的。在他們的實驗室裡或就在地面上,他們繼續研究著生命得以出現並最終改變這個星球的特殊環境。

We're trying to understand, with all the possible outcomes, what it was that made the uniqueness of our system. It seems like Earth's climate fixed itself to always be favourable to life.

我們試圖理解所有可能的結果,探究究竟是什麼使我們的系統具有獨特性。似乎地球的氣候固定不變,總是有利於生命的產生。

That's amazing. Each will explain the incredible saga from the viewpoint of their own discipline.

這很令人驚嘆。每個人都將從自己學科的角度來解釋這段不可思議的傳奇故事。

From the birth of our planet to today's ecosystems, it's a story punctuated by an incredible succession of lucky accidents. There's the analogy with the lottery.

從地球的誕生到今天的生態系統,這是一個被一連串令人難以置信的幸運事件打斷的故事。這與彩票有相似之處。

The probability of winning is tiny. So in the game of planetary formation, forming a solar system with our Earth is like winning the lottery.

獲勝的可能性很小。所以在行星形成的遊戲中,太陽系中誕生了地球就像中了彩票一樣。

Scientists are only now fitting together all the various chapters of this turbulent history, our history, that of a succession of helpful nudges, lucky chances and beneficial cataclysms. Without a helping hand from Jupiter and Saturn, without the Moon, without hurtling comets, without the power of volcanoes, without the genius of certain microorganisms?

直到現在,科學家們才將這段動蕩的歷史、我們的歷史、一系列有益的推動力、幸運的機遇和有益的災難的各個部分拼湊在一起。沒有木星和土星的幫助、沒有月亮、沒有飛馳的彗星、沒有火山的力量、沒有某些微生物的天賦,會怎麼樣呢?

We would not be here. It's possible that life is a one-off, existing nowhere else, that only our planet has all the conditions necessary for life as we know it.

我們就不會存在了。有可能生命是一次性的,在其他地方不存在,只有我們的星球具備我們所知道的生命存在的所有條件。

In that sense, Earth is probably unique. Although we may detect some life elsewhere, it will necessarily be completely different.

從這個意義上說,地球可能是獨一無二的。雖然我們可能會在其他地方發現一些生命,但那肯定是完全不同的。

It was this mind-blowing series of improbable events that made Earth the possibly unique life-bearing planet it now is. The idea that Earth may indeed be unique could have been spawned by this famous photo taken on the Apollo 8 mission in 1968.

正是這一系列令人興奮的不可能的事件,使地球成為現在這般可能是唯一的孕育生命的行星。地球可能確實是獨一無二的這一觀點大概是由1968年阿波羅8號任務拍攝的這張著名照片引發的。

It changed our way of looking at Earth. There is our planet, floating like an oasis in the magnificent emptiness of space.

它改變了我們看待地球的方式。這就是我們的星球,漂浮在浩瀚無垠的太空中,就像一片綠洲。

For the first time, there we all were — bacteria, mammals, insects and plants — on the same photo. Our planet… a unique ecosystem.

這是第一次,我們所有人——細菌、哺乳動物、昆蟲和植物——都出現在同一張照片上。我們的星球……一個獨一無二的生態系統。

And even today, this photo hints that Earth, veiled with clouds and enveloped in its thin atmosphere, could be alone in the universe. The first reason Earth was able to become this welcoming blue sphere is because it's at just the right distance from the Sun, in a narrow zone not too hot and not too cold, where the temperatures are compatible with liquid water and life.

即使在今天,這張照片也暗示著地球可能是宇宙中孤獨的存在,它被雲層覆蓋,被稀薄的大氣層包圍著。地球之所以能夠成為這個溫暖的藍色球體,第一個原因是它與太陽的距離剛剛好,處於一個既不太熱又不太冷、溫度適合液態水和生命存在的狹窄區域內。

But planetologists have discovered that Earth's very presence in this Goldilocks zone is itself due to an amazing stroke of luck. When the Solar System was still young, this zone came close to being taken over by the planet Jupiter.

但行星學家發現,地球出現在這片「宜居帶」本身就有驚人的運氣成分。當太陽系還很年輕的時候,這個整區域都幾乎被木星所佔據。

So how was Earth able to form here? Research into the answer to this puzzle has been carried out at Nice observatory.

那麼地球是如何在這裡形成的呢?尼斯天文臺已經在對這個謎題的答案進行研究了。

Alessandro Morbidelli has written a new account of the birth of our Solar System. Working on the origin of planetary systems is like being a detective.

亞歷山德羅·莫比德利(Alessandro Morbidelli)寫了一本關於太陽系誕生的新書。研究行星系統的起源就像做一名偵探。

You arrive at the crime scene, and use the clues to try to work out what happened. From our Solar System as it is, we try to reconstruct how it formed and developed.

你要到達犯罪現場,利用線索試圖弄清楚發生了什麼。從我們太陽系的現狀入手,我們試圖重建它的形成與發展。

When we come up with a scenario, we get a shiver of excitement, thinking that maybe we've got close to what actually happened. Planetologists start from the present position of the planets, attempting to hypothesise a scenario of the Solar System's formation with the help of computer simulations.

當我們想出一個場景時,我們會興奮地顫抖,認為也許我們已經接近實際發生的事情了。行星學家從行星的當前位置出發,試圖藉助計算機模擬來假設出太陽系形成的場景。

Our Solar System, like all planetary systems, formed from a cloud of gas and dust that surrounded the young Sun 4.5 billion years ago. But our Solar System seems to have a very different structure from the majority of planetary systems discovered over the last few years.

像所有的行星系統一樣,我們的太陽系是由45億年前圍繞年輕太陽的一團氣體和塵埃形成的。但我們的太陽系似乎有著與過去幾年發現的大多數行星系統都非常不同的結構。

We now think that our Solar System is pretty magic! A lot of chance events had to happen for it to be as it is.

我們現在認為我們的太陽系是相當神奇的!它之所以是這樣,是有很多偶然事件發生。

This suggests that our Solar System isn't a typical planetary system, but a relatively rare one. When we look at planets around other stars, we see that planets of a similar mass to Jupiter are found in Earth's spot.

這表明,我們的太陽系不是一個典型的行星系,而是一個相對罕見的行星系。當我們觀察其他恆星周圍的行星時,我們看到在地球的位置上發現了與木星質量相似的行星。

This is important. If Jupiter was in this spot, Earth wouldn't be here.

這非常重要。如果木星在這個位置,地球就不會在這裡了。

The discovery, outside our Solar System, of giant planets similar to Jupiter but much closer to their star, posed a serious puzzle for astronomers, because giant planets of that kind cannot form in such zones. Planets form in a disc of gas and dust that surrounds the young star.

在我們的太陽系之外發現了與木星相似但離恆星更近的巨型行星,這給天文學家帶來了一個嚴重的難題,因為這樣的巨型行星本不可能在這樣的區域中形成。行星是在圍繞年輕恆星的氣體和塵埃盤中形成的。

The giant planets form far out, where it's cold, where there's ice, which lets these planets grow to a huge size. Like a snowball rolling down a snowy hill, the planet grows ever bigger as it gathers to itself all the dust in its path.

這些巨大的行星形成於遙遠的地方,那裡很冷,有冰,這讓這些行星成長到了十分巨大的尺寸。就像雪球滾下雪山一樣,地球越滾越大,路上的灰塵越積越多。

When a planet gets big enough, when it acquires enough mass, it migrates inwards towards the star. Understanding this phenomenon was a real revolution.

當一顆行星變得足夠大,當它獲得足夠的質量時,它會向恆星內部遷移。理解這一現象是一場真正的革命。

Planetary migration explains why the majority of giant planets discovered elsewhere in the galaxy don't stay in their distant orbits. As they form, they spiral inwards towards their star.

行星遷移解釋了銀河系其他地方發現的大多數巨型行星不會停留在它們遙遠的軌道上的原因。當它們形成的時候,它們向呈內螺旋態朝向它們的恆星。

But in that case, why didn't our own giant, Jupiter, migrate closer to the Sun? Why did it stop just in time, leaving the space free for the future Earth?

但在這種情況下,為什麼我們自己的巨行星木星沒有遷移到離太陽更近的地方呢?為什麼它及時停下,為未來的地球留下了空間?

Saturn is very important. This is a giant planet too, and as we've studied the dynamic between Jupiter and Saturn, we've realised that Saturn was able to stop Jupiter's migration and even reverse it.

土星非常重要。這也是一顆巨大的行星,當我們研究木星和土星之間的動態關係時,我們已經意識到土星能夠阻止木星的遷移,甚至逆轉它。

So, Jupiter started migrating to the Sun, but when Saturn appeared there was a complicated gravitational effect which reversed the migration, and the planets moved further from the Sun. Thanks to Saturn, the giant planet Jupiter changed trajectory.

所以,木星開始向太陽遷移,但當土星出現時,一個複雜的引力作用逆轉了木星的遷移,使這顆行星離太陽更遠了。多虧了土星,巨大的木星改變了運行軌道。

It left the inner zone of the Solar System. And it was this change of course that saved Earth's future.

它離開了太陽系的內部區域。正是這種改變拯救了地球的未來。

Without the intervention of Saturn, Jupiter would have ended up in the zone where Earth now is. Earth would never have formed, and we would not be here.

如果沒有土星的介入,木星可能最後會在現在地球所在的區域。那麼地球就不會形成,我們也不會在這裡了。

Our planet was luckier than its future neighbour, Mars. Because on its migration Jupiter passed through the zone where Mars was forming.

我們的星球比它未來的鄰居火星要幸運得多。因為在木星的遷移過程中,它經過了火星形成的區域。

The giant planet swallowed up a lot of the material available, leaving only crumbs for Mars. Our neighbour would end up with one tenth the mass of Earth, which in turn reduced its possibility of maintaining an atmosphere favourable to life.

這顆巨大的行星吞噬了大量可用的物質,只留下了火星的碎屑。火星最終將只擁有地球十分之一的質量,這反過來減少了它維持適宜生命的大氣層的可能性。

We're understanding how planetary migration totally changes how the planets get distributed, their size, their position in space… And the collisions between these objects, before they stabilise as planets, make the system develop in its own particular way.

我們正在了解行星遷移如何完全改變行星的分布、大小、空間位置……在這些物體穩定成行星之前,它們之間的碰撞使這個系統以自己獨特的方式發展。

Narrowly saved by Saturn, our planet could keep on growing. And being just the right distance from the Sun, meant that it would later have liquid water on its surface.

由於土星的勉力拯救,我們的星球得以繼續成長。它與太陽的距離剛好合適,這意味著之後它的表面會有液態水存在。

And yet, 4.5 billion years ago our planet was completely dry. It formed in the rocky zone of the Solar System, gathering up dust with barely any water content.

然而,45億年前,我們的星球是完全乾旱的。它形成於太陽系的巖石區,聚集了幾乎不含水分的灰塵。

So where did this water, which would later give us our oceans, come from? After initially endangering our young Earth, Jupiter would give it a helping hand.

那麼,這些後來給我們帶來海洋的水是從哪裡來的呢?在危及我們年輕的地球之後,木星又會伸出其援助之手。

We think that the formation, the growth and the migration of Jupiter let these bodies which formed far out in the Solar System, cold bodies with water, be sent towards the inner zone, where they crashed into the still forming Earth, contributing their elements to it. These bodies, asteroids and comets, enriched the chaotic ball of matter which Earth then was with water.

我們認為,木星的形成、生長和遷移,讓這些在太陽系外形成的天體,冰冷的有水的天體,被送入了太陽系內部地帶,在那裡它們撞上了仍在形成的地球,把自己的元素貢獻給了地球。這些天體,小行星和彗星,豐富了當時還是由水組成的混沌球體的地球。

But as our planet started to solidify, the water molecules remained trapped under the surface, in the magma. Yet an essential mechanism for our planet's future was already in place and starting to bring some of that water to the surface.

但當我們的星球開始凝固時,水分子仍然被困在地表下的巖漿中。然而,我們星球未來的一個基本機制已經到位,開始把一些水帶到地表。

It's a mechanism that's still very active today. These volcanoes, these mountains of fire, have been helping to bring water to the surface from the very beginning.

這是一種至今仍然非常活躍的機制。這些火山從一開始就幫助把水帶到了地表。

In Earth's youth, there was a lot more volcanic activity than today. When you first think about a volcano, you think of lava, danger and life-threatening eruptions.

在地球形成的早期,火山活動比現在要多很多。當你想到火山時,你首先想到的是熔巖、危險和危及生命的物質噴發。

But volcanoes were essential for life as we know it.?It's the destruction of San Juan village, by the volcano Parícutin in 1944.

但正如我們所知,火山對生命是必不可少的存在。這是1944年被帕裡庫廷火山摧毀的聖胡安村莊。

The people had to move away. It was a real catastrophe.

人們不得不從那裡離開。這是一場真正的災難。

The artist has made the volcano quite small, yet the whole region was devastated. Yes, it appeared from nowhere in a cornfield.

這位藝術家把火山畫得很小,但整個地區卻都遭到了破壞。是的,它突然出現在玉米地裡。

No one could have expected it. When the village was destroyed it was still quite small.

沒有人會料到這一點。當村莊被摧毀時,它還很小。

Volcanoes aren't inimical to life. On the contrary, they were necessary for life to develop throughout Earth's existence.

火山對生命不是有害的。相反,它們是整個地球存在過程中生命發展所必需的。

Are such explosions common? They happen… not that often.

這種爆炸常見嗎?它們會發生…但不是經常發生。

I've been here six years, and I've seen four or five. With an explosion like that, ash may fall on surrounding villages.

我在這裡六年了,我見過四五次。像那樣程度的爆發,火山灰就可能會落到周圍的村莊上。

What's the gas made of? It's 95% water vapour.

那些氣體是由什麼構成的呢?其中95%是水蒸氣。

In all volcanoes around the world, it's mostly water vapour. The water vapour spat out by the volcanoes allowed the water trapped in the Earth's bowels to make its way to the surface.

在世界上所有的火山中,大部分都是水蒸氣。火山噴出的水蒸氣使得地球內部的水得以流到地表。

This has always been an essential mechanism for keeping our planet hydrated and alive. 4.4 billion years ago, thanks to the volcanoes, Earth's sky changed, filling with clouds.

這一直是保持地球水分和生命的基本機制。44億年前,由於火山爆發,地球的天空改變了,布滿了雲。

Diluvian rain started to lash the surface, it rained for millions of years, and the first oceans formed. Yet barely had they appeared than they could have just as quickly evaporated.

洪積的雨開始衝擊表面,雨下了幾百萬年,第一個海洋形成了。然而,它們剛一出現,就很快地蒸發了。

The difficult bit is having liquid water. You don't just need H2O, you need enough atmospheric pressure.

困難的是要有液態水。你不僅需要水,還需要足夠的大氣壓。

An atmosphere. On the Moon there's no atmosphere, so there's never been any liquid water.

需要大氣層。月球上沒有大氣層,所以從來沒有液態水。

If Earth's atmosphere hadn't been dense enough, the water would have evaporated into space in the form of vapour. Fortunately, the gas produced in abundance by the volcanoes maintained enough of an atmospheric pressure for Earth to be able to hold on to its early oceans.

如果地球的大氣層不夠稠密,水就會以水蒸氣的形式蒸發到太空中。幸運的是,火山噴發產生的大量氣體保持了足夠的大氣壓力,使地球能夠留住早期形成的海洋。

But the oceans of the young Earth soon faced another danger, that of freezing over. The Sun was still weak, 30% less bright than it is now.

但年輕地球上的海洋很快就面臨另一種危險,那就是結冰。太陽光照依然很弱,亮度比現在低30%。

Earth therefore needed a greenhouse effect to keep its surface warm enough and its water in a liquid state. This greenhouse effect appeared very early on in Earth's history, thanks to the water vapour and CO2 abundantly present in the atmosphere.

因此,地球需要溫室效應來使表面保持足夠的溫暖,並使水保持液態。由於大氣中大量存在的水蒸氣和二氧化碳,這種溫室效應在地球歷史上很早就出現了。

Today, of course, we know that CO2, increased by human activity, is a bad thing. Too much isn't good.

我們當然知道,如今人類活動增加的二氧化碳是一件壞事。太多並不好。

But we needed some back then. And still do.

但我們當時需要一些這種氣體。現在也仍然需要。

If there wasn't a bit in the atmosphere, the surface temperature would be 15 degrees colder. And back then, with the Sun younger and less bright, it would have been much colder.

如果大氣中一點兒二氧化碳都沒有,地球表面的溫度就會降低15度。那時,太陽的年齡更小,亮度也更低,溫度就低得多。

Earth would have been frozen, about minus 60 degrees, so not favourable to life. The volcanoes were yet again contributing to making Earth habitable.

地球會被凍住,只有大約零下60度,不利於生命存活。是火山再次使地球變得適於居住。

In their exhalations they were constantly spewing out huge quantities of CO2 along with the water vapour. The CO2 spat out by the volcanoes accumulated, the greenhouse effect increased, the ice melted and the oceans thawed.

在它們盆出的氣體中,不斷地伴隨著水蒸氣排出大量的二氧化碳。火山噴發出的二氧化碳積累起來,溫室效應加劇,使得冰融化、海洋解凍。

We think this happened 400 to 500 million years ago. We call this period Snowball Earth.

我們認為這發生在4億到5億年前。我們稱這個時期為冰雪地球。

Earth emerged from it like that. The greenhouse effect increased, and we got back a climate with liquid water, favourable to life.

地球就是這樣誕生的。溫室效應增強了,我們又恢復了有液態水的氣候,有利於生命的生存。

But with the constant eruptions, the CO2 from the volcanoes was steadily accumulating in the young Earth's atmosphere. The greenhouse effect could have got out of control, turning our planet into a furnace.

但隨著火山的不斷噴發,火山噴發出的二氧化碳在年輕的地球大氣中穩步積累。溫室效應可能會失去控制,把我們的地球變成一個大熔爐。

Fortunately, there was a safety valve. CO2 can dissolve in water.

幸運的是,存在有一個安全閥。二氧化碳能溶於水。

Over millions of years, it is trapped in calcareous formations, and no longer acts as a greenhouse gas. It remains trapped, inert, at the bottom of the ocean, in mineral form.

經過數百萬年,它被困在鈣質的結構中,不再作為溫室氣體而存在。它以礦物的形式被困在海底,是惰性的。

The quantity of CO2 in the atmosphere, then, varies depending on the amount of liquid water on Earth's surface. Over very long timescales, this mechanism regulates our planet's climate.

因此,大氣中二氧化碳的數量取決於地球表面液態水的數量。在很長一段時間內,這種機制調節著地球的氣候。

A fascinating thing about Earth, which may make it unique, is that all through its very long existence, all four and a half billion years, variations in the luminosity of the Sun have been compensated for by a variable greenhouse effect. It's like a sort of geophysical thermostat keeping the Earth always inhabitable, with oceans on the surface.

地球有一件迷人的事情,這可能使它獨一無二,那就是在它漫長的存在過程中,在45億年的時間裡,太陽亮度的變化被可變的溫室效應抵消了。它就像地球物理的恆溫器一樣,表面有海洋,使地球始終適宜居住。

But this thermostat needed one more tweak to get it working perfectly and make our planet truly favourable to life. Over hundreds of millions of years, all the CO2 in the atmosphere could have ended up trapped in the form of calcareous rock at the bottom of the ocean.

但這個恆溫器還需要再微調一下,才能讓它完美運轉,讓我們的星球真正適合生命生存。經過數億年的時間,大氣中所有的二氧化碳都可能以海洋底部鈣質巖石的形式被封存。

There wouldn't have been enough in circulation to keep the thermostat going and it would have broken down. A mechanism possibly unique to our planet allowed for the reinjection of CO2 into the atmosphere: plate tectonics.

沒有足夠的循環來保持恆溫器運轉的話它就會壞掉。一種可能是地球獨有的機制允許二氧化碳重新注入大氣之中:板塊構造。

You have to realise that the Earth has a sort of crust of cold and solid rock. Inside, there's warmer rock, the mantle, which changes shape.

你必須認識到,地球有一種由冰冷而堅硬的巖石構成的外殼。其內部有更溫暖的巖石——地幔,它會改變形狀。

This is softer. So you might imagine that the crust forms a solid, complete shell, like an eggshell around a softer inside.

這一層更柔軟一些。所以你可以想像成地殼形成了一個堅實的完整的外殼,就像蛋殼包裹著更軟的內部一樣。

But that's not right. The movements of the shifting rock on the inside were powerful enough to rub up against the crust and crack it in places.

但這還不對。內部移動的巖石的運動非常強大,足以摩擦地殼並使其碎裂。

The Earth's crust is fragmented into ten plates, which are displaced by the movements of the mantle. Where the plates come together, they crunch over each other, dragging the rocks that were at the bottom of the ocean deep into the bowels of the Earth.

地球的地殼裂成了十個板塊,這些板塊由於地幔的運動而移位。在板塊接觸的地方,它們互相擠壓,將海底的巖石拖到地球深處。

Thus does the CO2 recycling begin. Under the enormous pressure and heat, the rocks melt, and the magma is spewed back out onto the surface, taking the CO2 with it.

二氧化碳的回收就這樣開始了。在巨大的壓力和熱量下,巖石融化,巖漿噴出地表,二氧化碳也隨之噴出。

The CO2 escapes in gas form during volcanic eruptions. Finally back in the atmosphere, the CO2 may or may not be captured again by the oceans, depending on climatic conditions.

在火山爆發時,二氧化碳以氣體形式逃逸。最後回到大氣中,二氧化碳可能會被海洋再次捕獲,也可能不會,這取決於氣候條件。

The circle is complete. It's a very particular geophysical thermostat, which we think has really controlled the climatic conditions on Earth and made life possible.

這個循環完成了。它是一個非常特殊的地球物理恆溫器,我們認為它真的控制了地球上的氣候條件,讓生命成為可能。

If you changed the plate tectonics just a little, having slightly more or fewer than ten plates, the recycling and CO2 concentration would have been different, and the biosphere would have evolved differently. And this begs another important question.

如果你稍微改變一下板塊構造,有稍微多於或少於十個板塊,那麼循環和二氧化碳的濃度就會有所不同,生物圈也會有不同的進化。這引出了另一個重要的問題。

This plate tectonics, which seems to be the key, the key to life on Earth… Is plate tectonics something really common in the rest of the galaxy, or something unique or very rare?

這種板塊構造似乎就是關鍵所在,似乎是地球生命的關鍵……板塊構造在銀河系的其他地方真的很普遍嗎?還是在地球獨一無二或非常罕見?

In the Solar System, you don't find it anywhere else. Plate tectonics may be the factor which Earth's neighbouring planets lacked for life to appear and survive there.

在太陽系中,你在其他任何地方都找不到它。板塊構造可能是地球的鄰近行星沒有生命出現和生存的因素。

Yet one of the Solar System's other rocky planets did get off to a good start. Early in its history, with volcanoes, CO2 and water, Mars enjoyed an environment similar to Earth's.

然而,太陽系的其他巖石行星中的一顆確實有了一個良好的開端。在火星早期的歷史上,有火山、二氧化碳和水,火星曾享受過與地球相似的環境。

So there was an environment. Imagine a blue Mars with lakes and rivers.

所以當時是有這麼一個環境的。想像一個有湖泊和河流的藍色火星。

Some think there was an ocean in the northern hemisphere. So it was an environment favourable to life.

有些人認為在火星的北半球有海洋。所以這是一個有利於生命存在的環境。

All would seem to have been set up, then, for the planet to function in a similar fashion. The current state of the red planet, however, clearly shows that something went wrong.

這一切似乎都是為地球以類似的方式運行而設置的。然而,這顆紅色星球目前的狀態清楚地表明,有什麼問題出現了。

Mars cooled down much faster. Since Mars is half the size of Earth, it's a bit like comparing a huge pot of hot water to a cup of tea.

火星冷卻得更快。由於火星是地球的一半大小,這有點像把一大壺熱水與一杯茶作比較。

The big pot cools slower than the cup of tea, which is Mars. The inside cooled faster.

大壺的熱水比小杯的茶冷卻得慢,後者即指火星。其內部冷卻得更快。

So there was no chance, as we understand it, for plate tectonics to arise. There was no recycling that could maintain a climate favourable to oceans for billions of years.

因此,按照我們的理解,板塊構造是不可能產生的。沒有什麼再循環可以維持幾十億年對海洋有利的氣候。

Mars had hundreds of millions of years. And thereafter it became a very sterile planet.

火星存在了數億年。從那以後,它就變成了一個貧瘠的星球。

Mars's tragedy is that it is too small, and fell into a deadly spiral. Because of its smaller mass, there was insufficient gravity to hold on to its atmosphere, the drop in atmospheric pressure was inexorable, and the solar wind swept it all away.

火星的悲劇在於它太小了,而且陷入了致命的漩渦。由於它的質量較小,沒有足夠的重力來抓住它的大氣層,大氣壓力的下降就是不可避免的,太陽風把它們都吹走了。

Some of the water evaporated, the rest froze. Blue Mars became red Mars, a victim of its own small size.

一些水蒸發了,其餘的結冰了。藍色火星變成了紅色火星,成為了自身體積小的犧牲品。

So you think, Earth is just the right size! So why is there no plate tectonics on Venus, which is the same size as Earth?

所以你看吧,地球的大小就正合適!那麼,為什麼和地球一樣大小的金星上沒有板塊構造運動呢?

Why is that? Unlike Earth, Venus has hardly any water.

這是為什麼?與地球不同的是,金星幾乎沒有水。

The water's all gone, and the mantle is very dry, not very lubricated. It can't move much or displace any plates on the surface.

所有的水都沒了,地幔非常乾燥,不潤滑。它不能大幅移動或移動表面上的任何板塊。

So Venus has a sort of unbroken shell all around the planet. It doesn't have the mechanism that Earth has.

所以金星在行星周圍有一層完整的外殼。它沒有地球的運作機制。

So it's not just important to be the right size, but to have water in the mantle. Earth has enough water to lubricate its plate tectonics.

所以不僅僅要大小合適,地幔中有水也很重要。地球有足夠的水來潤滑它的板塊構造運動。

Venus doesn't. And yet the two planets were formed from the same materials.

金星則沒有。然而,這兩顆行星是由相同的物質構成的。

One very special event during the Earth's youth could have hydrated its depths. This is the idea.

地球年輕時發生的一件非常特殊的事件可能使它深度水化。是這樣的。

For the mantle to have got sufficiently hydrated, sufficiently "lubricated", early in its existence Earth suffered a huge cataclysm. We think that the young Earth was struck by another planet the size of Mars, which we call Theia.

為了讓地幔得到足夠的水分和潤滑,地球在其存在的早期經歷了巨大的災難。我們認為年輕的地球被另一顆火星大小的行星撞擊了,我們稱之為忒伊亞。

A few tens of millions of years after its birth, Earth suffered a cataclysm which almost destroyed it outright. The chaos of the Solar System's origins still reigned.

地球誕生後幾千萬年,經歷了一場大災難,幾乎將它完全摧毀。太陽系起源的混亂仍然存在。

Imagine, around Earth, hundreds of moons or dozens of the planet Mars. Colliding repeatedly, these objects grow and form planets.

想像一下,圍繞著地球,有數百顆衛星或數十顆火星。它們不斷的碰撞,這些物體成長並形成行星。

Suddenly, an object the size of Mars comes towards our Earth, and crashes into the surface at a speed something like 15 kilometres per second. Theia crashed into Earth.

突然,一個火星大小的物體朝地球飛來,並以大約每秒15公裡的速度撞向地球表面。忒伊亞撞上了地球。

The energy released by this enormous collision was equivalent to hundreds of billions of hydrogen bombs. The impact is so violent that the impacting object is destroyed.

這次巨大碰撞釋放的能量相當於數千億顆氫彈。撞擊如此猛烈以致於撞擊物都被摧毀了。

The surface of the Earth is completely liquefied, and the core of the impacting body penetrates the Earth's mantle, becoming part of the Earth's core. We think the Earth's core fused with that of the impacting body.

地球表面完全液化,撞擊體的核穿透地幔,成為地核的一部分。我們認為地核與撞擊體的地核融合在了一起。

The collision was so violent that the water contained in Theia was driven deep into Earth's core, mixing with the water already present there. In this way, Theia hydrated the depths of Earth's mantle, making it possible later for the plate tectonics system to function.

這次碰撞是如此猛烈,以至於忒伊亞所含的水被打入地核深處,與已經存在的水混合在了一起。通過這種方式,忒伊亞將地球地幔的深處水化,使得後來的板塊構造系統能夠發揮作用。

It's speculative, but if it's right it's impressive. It shows us that for life to have existed on Earth all this time we needed that chance impact very early in Earth's history, to hydrate the mantle, maintain its lubrication, and have this phenomenon, this geophysical thermostat, all throughout the planet's existence.

這是推測性運動的,但如果它是正確的,就十分令人驚訝了。它告訴我們,要想在地球上一直存在有生命,我們就需要在地球歷史的早期有這種偶然的撞擊,使地幔水化,保持其潤滑,並使這種現象,這種地球物理恆溫器,貫穿整個地球的存在。

This seeming catastrophe would end up being beneficial in another way, as Earth gained a new companion, which would play a major role in the blossoming of our ecosystem. Out of the cloud of debris resulting from the collision, a new body would gradually form.

隨著地球獲得了一個新夥伴,這個表面上的災難最終會以另一種方式帶來好處,它將在我們生態系統的繁盛中發揮重要作用。在碰撞產生的碎片雲中,一個新的物體會逐漸形成。

The Moon. The Earth-Moon system is unique in the Solar System and, as far as we now, in the galaxy.

那就是月亮。地月系統在太陽系中是獨一無二的,到目前為止,在銀河系中也是獨一無二的。

It's a very particular system where both objects are large objects. This is why certain astronomers talk of a "double planet".

這是一個非常特殊的系統,兩個物體都是大物體。這就是某些天文學家稱之為「雙行星」的原因。

Barely had it come into existence, then the Moon was already exerting a powerful influence on the Earth because of its considerable size. The history of the Earth-Moon relationship has been studied very closely, thanks to the Apollo missions.

月球還沒有形成,就已經因其巨大的體積對地球產生了強大的影響。由於阿波羅計劃,地月關係的歷史已經被非常仔細地進行了研究。

The Apollo missions placed reflectors on the Moon's surface. These reflectors are used today to reflect back laser beams emitted from Earth, such as this one behind me.

阿波羅計劃在月球表面安裝了反射器。這些反射器現在被用來反射從地球發射的雷射束,比如我身後的這個。

There's a regular emission from here, the Calern plateau in France. Today, many observatories around the world, like this one in the Alpes-de-Haute-Provence, monitor the Moon closely.

這裡有一個定期的發射,法國的卡倫高原。今天,世界各地的許多天文臺,比如位於上普羅旺斯阿爾卑斯的這個天文臺,都在密切監測月球。

Every night, scientists use a laser beam to make a precise measurement of its distance from Earth. These are important experiments because we can measure how long it takes the laser beam to go to the Moon and back.

每天晚上,科學家們都會用雷射束精確測量它與地球的距離。這些實驗很重要,因為我們可以測量雷射束往返月球所需的時間。

So we can measure, in real time, the distance to the Moon. One major finding, which we sort of knew before but are now sure of, is that the Moon is moving away.

所以我們就可以實時測量到月球的距離。一個主要的發現是,月球正在遠離地球,這是我們以前知道的,但現在可以確定的。

It's moving away at a speed of 3 or 4 centimetres per year. These measurements have shown that, when it formed, the Moon was much closer to the Earth than it is today.

它以每年3到4釐米的速度向遠離去。這些測量結果表明,月球形成時與地球的距離要比現在近得多。

Soon after the Moon formed, if anyone had been here to see the Moon, it would have been gigantic in the sky because it was so close. Now it's 380,000 km from Earth.

月球形成後不久,如果有人來這裡看月亮的話,它在天空中一定是巨大的,因為它離我們很近。現在它距離地球有38萬公裡。

But 4 billion years ago we think it was only 15,000 km distant. The proximity of the Moon had a first consequence of creating bigger tides and therefore maybe stimulating biological evolution.

但40億年前,我們認為這個距離只有15000公裡遠。月球靠近地球的第一個後果是造成更大的潮汐,因此可能會刺激生物進化。

The tides caused by the Moon churned up the oceans and contributed to the dynamism of our ecosystem. The mutual attraction between the two bodies also had a crucial effect on Earth's rotational axis.

由月球引起的潮汐攪動海洋,促進了我們生態系統的活力。兩個物體之間的相互吸引對地球的旋轉軸也有至關重要的影響。

The effect wasn't just the tides, it was much more. It stabilised the famous tilt, the angle of 23 degrees by which Earth's axis is tilted in relation to its trajectory around the Sun.

影響不僅僅是帶來潮汐,還有更多。它穩定了著名的傾斜角度(23度,地軸相對於繞太陽軌道傾斜)。

And this angle has stayed constant for billions of years. If the Moon hadn't been there, Earth's rotational axis would have oscillated, causing rapid changes in the climate.

這個角度數十億年來都保持不變。如果月球沒有在那裡,地球的轉軸就會振蕩,導致氣候的迅速變化。

This could have had huge consequences on evolution. With rapidly alternating periods of glaciation and warming, for example.

這可能對進化產生了巨大的影響。例如冰川作用和氣候變暖的快速交替時期。

The Moon helped the Earth maintain a climate stable enough for the slow and gradual evolution of life. Without the Moon, the Earth would have been faced with the same upheavals as its neighbour Mars.

月球幫助地球維持了足夠穩定的氣候,使生命得以緩慢而漸進地進化。如果沒有月球,地球將面臨與它的鄰居火星一樣的劇變。

The moons of Mars, Phobos and Deimos, are so small that they play no stabilising role on the rotational axis. There have been very big variations in the rotational axis of Mars.

火星、火衛一和火衛二的衛星都太小了,它們在轉軸上起不到穩定作用。火星的轉軸有很大的變化。

What's more, this rotational axis has moved all around the surface of Mars. Mars became a desert; Earth, a garden of Eden.

更重要的是,這個旋轉軸繞著火星表面轉動。火星變成了沙漠;地球,則是一座伊甸園。

The present Earth-Moon system is the result of a long series of accidents, making the Earth and Moon a unique couple. Earth now had a stable climate, an atmosphere and liquid water.

目前的地月系統是一系列意外事件的結果,使地球和月球成為獨一無二的一對。地球現在有了穩定的氣候、大氣和液態水。

Surely everything was perfectly set up for life to appear and evolve. But Earth still lacked the basic ingredients of life: organic molecules.

毫無疑問,一切都為生命的出現和進化做好了完美的準備。但是地球仍然缺乏生命的基本成分:有機分子。

All living things on Earth are made of the same building blocks: long carbon-based molecules. Scientists now think that a large proportion of these molecules came from outside planet Earth.

地球上所有的生物都是由相同的構件組成的:長碳基分子。科學家們現在認為,這些分子中的很大一部分來自地球以外的行星。

The organic molecules, the basic elements necessary for life, are found in space. They're in meteorites.

有機分子是生命所必需的基本元素,是在太空中被發現的。他們在隕星之中。

Some are 60% organic material, which is huge. And a lot fell to Earth.

其中一些含有60%的有機物質,這是一個巨大的數字。很多落到了地球上。

The original organic molecules, which may have sown the seeds of life on Earth were present in the distant cold zone of the solar system. But how did these building blocks of life travel to our planet?

最初的有機分子可能在地球上播下了生命的種子,它們存在於太陽系遙遠的寒冷地帶。但是這些生命的組成部分是如何到達我們的星球的呢?

The Rosetta mission, the first to ever attempt landing a module on a comet, shed some light on this mystery. Jean-Pierre Bipring was one of the scientists behind this audacious mission.

羅塞塔任務是首次嘗試在彗星上著陸太空艙,這為解開這個謎團提供了一些線索。讓-皮埃爾·比普林(Jean-Pierre Bipring)是推動這項大膽任務背後的科學家之一。

This is what we saw on 14th July 2014. When we got this, we thought: "We can't land on that, it's not feasible."

這是我們在2014年7月14日看到的。當我們得到這個的時候,我們想著:「我們不能在上面著陸,這是不可行的。」

This is tiny. The whole thing is only four kilometres. And it's revolving around an awkward axis.

這太小了。整個星球只有4公裡,而且它繞著一個很尷尬的軸旋轉。

We thought we'd never find a spot to set down on, it was crazy. A few months later, the probe Philae managed despite all the difficulties to touch down on the comet Chury.

我們以為我們永遠找不到落腳的地方,這太瘋狂了。幾個月後,儘管困難重重,「菲萊」號探測器還是成功降落在了「丘裡」彗星上。

Here you see Philae's leg, an object made just a few years ago, and here, the oldest object in the Solar System, the same as when it formed 4.6 billion years ago. It was the first time, and it won't happen again soon, that we set something down on a comet.

這裡你可以看到菲萊的支架,它是幾年前製造的,這裡是太陽系中最古老的物體,保持著和46億年前形成時相同的模樣。這是我們第一次在彗星上放置東西,而且不會很快再次發生。

With the first analyses, the scientists realised that comets are very different from what they had supposed. There's no water on this comet's surface.

通過最初的分析,科學家們意識到彗星與他們所認為的非常不同。這顆彗星表面沒有水。

There isn't an ounce of ice. We thought it'd be mostly ice, with a few molecules.

連一盎司的冰都沒有。我們原以為它主要是冰,只有一些分子微粒。

Not at all. All we see here is organic material.

根本不是這樣。我們在這裡看到的都是有機物。

Thanks to the Rosetta mission, scientists discovered that comets are abundant in the building blocks of life. Up until then, they had thought that only asteroids, little rocky bodies, were thus endowed.

多虧了羅塞塔號任務,科學家們發現彗星是構成生命的重要組成部分。在此之前,他們一直認為只有小行星,巖石小天體,才有這樣的天賦。

Since the birth of the Solar System, comets and asteroids have gravitated in the colder regions, where they capture and store these original organic molecules. Then these comets and asteroids, veritable messengers of life, transport these molecules into the inner zones of the Solar System.

自從太陽系誕生以來,彗星和小行星就一直被吸引到較冷的區域,在那裡它們捕獲並儲存了這些原始的有機分子。然後這些彗星和小行星,真正的生命信使,把這些分子運送到太陽系的內部區域。

As they pass close to a planet, they disseminate these building blocks onto the surface, providing it with the wherewithal for life. Scientists are keen to undertake laboratory analysis of organic molecules similar to those which fell into Earth's oceans.

當它們接近一顆行星時,它們會把這些組成部分散布到行星表面,為行星提供生命所需的物資。科學家們熱衷於對有機分子進行實驗室分析,即類似於那些落入地球海洋的分子。

This was the aim of the Hayabusa2 mission, launched by the Japanese space agency: to bring back to Earth a few fragments of this original organic matter. The sample was collected in July 2019,300 million kilometres from Earth.

這就是由日本航天局發射的隼鳥2號任務的目標:將這些原始有機物的一些碎片帶回地球。該樣本於2019年7月在距離地球3億公裡的地方採集。

The mission was a success. This is the moment when it touched down.

這次任務取得了成功。這就是飛行器降落的時刻。

You see the leg touching down. It's mind-blowing.

你看到那個支架著地了。這令人十分興奮。

Then you see it take off again. The principle for taking samples is for it not to linger.

然後你看到它再次起飛。採集樣本的原則是不要逗留太久。

It touches down, fires a bullet, and leaves again with the debris. It takes a few seconds.

它著陸後發射了一顆子彈,然後帶著那些碎片再次離開。這隻花了幾秒鐘的時間。

And it all happens very far from Earth, of course. It's completely mind-blowing.

當然,這一切都發生在離地球很遠的地方。這真的是令人超級興奮。

We hope that in the sample there's carbonaceous material, from which, we think, life on Earth began. The probe is bringing back a tenth of a gram of these precious building blocks of life, similar to those which landed on the planets of our Solar System some four billion years ago.

我們希望樣本中含有碳質物質,我們認為地球上的生命是從碳質物質開始的。探測器帶回了十分之一克珍貴的構成生命的物質,類似於40億年前降落在太陽系行星上的物質。

From this material, we want to find out what the initial ingredients were which, in the waters of Earth's primordial oceans, made possible the great chain of terrestrial biology. Comets and asteroids could be the missing links of a long chain.

從這些材料中,我們想找出最初的成分是什麼,是什麼在地球原始海洋的水中,使陸地生物偉大鏈條的形成成為可能。彗星和小行星可能是長鏈中缺失的一環。

The chain began with the simple molecules found in the early cloud dusts, and culminated with the building blocks of life from which life on Earth first sprang. The chain leading to life.

這條鏈從早期雲塵中發現的簡單分子開始,最終形成了地球上生命最初起源的構成要素。是一條通往生命的長鏈。

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