地球经常会发现什么事（环境与科学-如果）

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.，我来为大家讲解一下关于地球经常会发现什么事?跟着小编一起来看一看吧!

地球经常会发现什么事

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.

如果我们花时间去观察大自然，会发现它为我们展现了迷人的奇观。随着时间的推移，我们星球上的居民编织了协作、共生、依赖和掠夺的复杂关系。

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

地球是一个满是生命的星球。奔跑着的、爬行着的或飞翔着的，到处都是生命。

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，为了让这些美丽的多样性得以增殖，地球必须在大约40亿年的时间里一直为它们提供一个有利的环境。那么，使地球上生命繁盛的条件是什么呢？

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.

这些条件会不会出现在其他地方，导致一种另类的生态系统呢？为了回答这些问题，科学家在宇宙中寻找着生命的迹象。

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.

他们建造了巨大的望远镜，用它来探测宇宙，聆听星星的低语。但太空一直坚决地保持着沉默。

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.

科学家们已经向太阳系的边缘发射了探测器。但他们发回的都是与对生命有害的行星的图像。

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，在过去的25年里，天文学家仅在我们的星系中就发现了成千上万种不同的行星。有那么多奇怪的世界，却没有生命的迹象。

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

没有任何一个星球与我们的地球相似。所以地球真的是独一无二的吗？

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.

在本期节目中，科学家将讲述有关地球如何发展的迷人故事，即这个由冰和尘埃组成的球体是如何成为一颗具有生命的星球的。在他们的实验室里或就在地面上，他们继续研究着生命得以出现并最终改变这个星球的特殊环境。

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.

我们试图理解所有可能的结果，探究究竟是什么使我们的系统具有独特性。似乎地球的气候固定不变，总是有利于生命的产生。

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

这很令人惊叹。每个人都将从自己学科的角度来解释这段不可思议的传奇故事。

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.

从地球的诞生到今天的生态系统，这是一个被一连串令人难以置信的幸运事件打断的故事。这与有相似之处。

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.

获胜的可能性很小。所以在行星形成的游戏中，太阳系中诞生了地球就像中了一样。

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?

直到现在，科学家们才将这段动荡的历史、我们的历史、一系列有益的推动力、幸运的机遇和有益的灾难的各个部分拼凑在一起。没有木星和土星的帮助、没有月亮、没有飞驰的彗星、没有火山的力量、没有某些微生物的天赋，会怎么样呢？

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.

我们就不会存在了。有可能生命是一次性的，在其他地方不存在，只有我们的星球具备我们所知道的生命存在的所有条件。

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

从这个意义上说，地球可能是独一无二的。虽然我们可能会在其他地方发现一些生命，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.

正是这一系列令人兴奋的不可能的事件，使地球成为现在这般可能是唯一的孕育生命的行星。地球可能确实是独一无二的这一观点大概是由1968年阿波罗8号任务拍摄的这张著名照片引发的。

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

它改变了我们看待地球的方式。这就是我们的星球，漂浮在浩瀚无垠的太空中，就像一片绿洲。

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

这是第一次，我们所有人——细菌、哺乳动物、昆虫和植物——都出现在同一张照片上。我们的星球……一个独一无二的生态系统。

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，这张照片也暗示着地球可能是宇宙中孤独的存在，它被云层覆盖，被稀薄的大气层包围着。地球之所以能够成为这个温暖的蓝色球体，第一个原因是它与太阳的距离刚刚好，处于一个既不太热又不太冷、温度适合液态水和生命存在的狭窄区域内。

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.

但行星学家发现，地球出现在这片“宜居带”本身就有惊人的运气成分。当太阳系还很年轻的时候，这个整区域都几乎被木星所占据。

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

那么地球是如何在这里形成的呢？尼斯天文台已经在对这个谜题的答案进行研究了。

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.

亚历山德罗·莫比德利(Alessandro Morbidelli)写了一本关于太阳系诞生的新书。研究行星系统的起源就像做一名侦探。

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.

你要到达犯罪现场，利用线索试图弄清楚发生了什么。从我们太阳系的现状入手，我们试图重建它的形成与发展。

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.

当我们想出一个场景时，我们会兴奋地颤抖，认为也许我们已经接近实际发生的事情了。行星学家从行星的当前位置出发，试图借助计算机模拟来假设出太阳系形成的场景。

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.

像所有的行星系统一样，我们的太阳系是由45亿年前围绕年轻太阳的一团气体和尘埃形成的。但我们的太阳系似乎有着与过去几年发现的大多数行星系统都非常不同的结构。

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.

我们现在认为我们的太阳系是相当神奇的！它之所以是这样，是有很多偶然事件发生。

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.

这表明，我们的太阳系不是一个典型的行星系，而是一个相对罕见的行星系。当我们观察其他恒星周围的行星时，我们看到在地球的位置上发现了与木星质量相似的行星。

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

这非常重要。如果木星在这个位置，地球就不会在这里了。

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.

在我们的太阳系之外发现了与木星相似但离恒星更近的巨型行星，这给天文学家带来了一个严重的难题，因为这样的巨型行星本不可能在这样的区域中形成。行星是在围绕年轻恒星的气体和尘埃盘中形成的。

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.

这些巨大的行星形成于遥远的地方，那里很冷，有冰，这让这些行星成长到了十分巨大的尺寸。就像雪球滚下雪山一样，地球越滚越大，路上的灰尘越积越多。

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

当一颗行星变得足够大，当它获得足够的质量时，它会向恒星内部迁移。理解这一现象是一场真正的革命。

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.

行星迁移解释了银河系其他地方发现的大多数巨型行星不会停留在它们遥远的轨道上的原因。当它们形成的时候，它们向呈内螺旋态朝向它们的恒星。

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?

但在这种情况下，为什么我们自己的巨行星木星没有迁移到离太阳更近的地方呢？为什么它及时停下，为未来的地球留下了空间？

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。这也是一颗巨大的行星，当我们研究木星和土星之间的动态关系时，我们已经意识到土星能够阻止木星的迁移，甚至逆转它。

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，木星开始向太阳迁移，但当土星出现时，一个复杂的引力作用逆转了木星的迁移，使这颗行星离太阳更远了。多亏了土星，巨大的木星改变了运行轨道。

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

它离开了太阳系的内部区域。正是这种改变拯救了地球的未来。

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.

如果没有土星的介入，木星可能最后会在现在地球所在的区域。那么地球就不会形成，我们也不会在这里了。

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

我们的星球比它未来的邻居火星要幸运得多。因为在木星的迁移过程中，它经过了火星形成的区域。

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.

这颗巨大的行星吞噬了大量可用的物质，只留下了火星的碎屑。火星最终将只拥有地球十分之一的质量，这反过来减少了它维持适宜生命的大气层的可能性。

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.

我们正在了解行星迁移如何完全改变行星的分布、大小、空间位置……在这些物体稳定成行星之前，它们之间的碰撞使这个系统以自己独特的方式发展。

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.

由于土星的勉力拯救，我们的星球得以继续成长。它与太阳的距离刚好合适，这意味着之后它的表面会有液态水存在。

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，45亿年前，我们的星球是完全干旱的。它形成于太阳系的岩石区，聚集了几乎不含水分的灰尘。

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.

那么，这些后来给我们带来海洋的水是从哪里来的呢？在危及我们年轻的地球之后，木星又会伸出其援助之手。

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.

我们认为，木星的形成、生长和迁移，让这些在太阳系外形成的天体，冰冷的有水的天体，被送入了太阳系内部地带，在那里它们撞上了仍在形成的地球，把自己的元素贡献给了地球。这些天体，小行星和彗星，丰富了当时还是由水组成的混沌球体的地球。

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.

但当我们的星球开始凝固时，水分子仍然被困在地表下的岩浆中。然而，我们星球未来的一个基本机制已经到位，开始把一些水带到地表。

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.

这是一种至今仍然非常活跃的机制。这些火山从一开始就帮助把水带到了地表。

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，火山活动比现在要多很多。当你想到火山时，你首先想到的是熔岩、危险和危及生命的物质喷发。

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

但正如我们所知，火山对生命是必不可少的存在。这是1944年被帕里库廷火山摧毁的圣胡安村庄。

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

人们不得不从那里离开。这是一场真正的灾难。

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

这位艺术家把火山画得很小，但整个地区却都遭到了破坏。是的，它突然出现在玉米地里。

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

没有人会料到这一点。当村庄被摧毁时，它还很小。

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

火山对生命不是有害的。相反，它们是整个地球存在过程中生命发展所必需的。

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

这种爆炸常见吗？它们会发生…但不是经常发生。

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

我在这里六年了，我见过四五次。像那样程度的爆发，火山灰就可能会落到周围的村庄上。

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

那些气体是由什么构成的呢？其中95%是水蒸气。

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，大部分都是水蒸气。火山喷出的水蒸气使得地球内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.

这一直是保持地球水分和生命的基本机制。44亿年前，由于火山爆发，地球的天空改变了，布满了云。

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.

洪积的雨开始冲击表面，雨下了几百万年，第一个海洋形成了。然而，它们刚一出现，就很快地蒸发了。

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

困难的是要有液态水。你不仅需要水，还需要足够的大气压。

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

需要大气层。月球上没有大气层，所以从来没有液态水。

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.

如果地球的大气层不够稠密，水就会以水蒸气的形式蒸发到太空中。幸运的是，火山喷发产生的大量气体保持了足够的大气压力，使地球能够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.

但年轻地球上的海洋很快就面临另一种危险，那就是结冰。太阳光照依然很弱，亮度比现在低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，地球需要温室效应来使表面保持足够的温暖，并使水保持液态。由于大气中大量存在的水蒸气和二氧化碳，这种温室效应在地球历史上很早就出现了。

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

我们当然知道，如今人类活动增加的二氧化碳是一件坏事。太多并不好。

But we needed some back then. And still do.

但我们当时需要一些这种气体。现在也仍然需要。

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.

如果大气中一点儿二氧化碳都没有，地球表面的温度就会降低15度。那时，太阳的年龄更小，亮度也更低，温度就低得多。

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

地球会被冻住，只有大约零下60度，不利于生命存活。是火山再次使地球变得适于居住。

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.

在它们盆出的气体中，不断地伴随着水蒸气排出大量的二氧化碳。火山喷发出的二氧化碳积累起来，温室效应加剧，使得冰融化、海洋解冻。

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

我们认为这发生在4亿到5亿年前。我们称这个时期为冰雪地球。

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

地球就是这样诞生的。温室效应增强了，我们又恢复了有液态水的气候，有利于生命的生存。

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.

但随着火山的不断喷发，火山喷发出的二氧化碳在年轻的地球大气中稳步积累。温室效应可能会失去控制，把我们的地球变成一个大熔炉。

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

幸运的是，存在有一个安全阀。二氧化碳能溶于水。

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.

经过数百万年，它被困在钙质的结构中，不再作为温室气体而存在。它以矿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，大气中二氧化碳的数量取决于地球表面液态水的数量。在很长一段时间内，这种机制调节着地球的气候。

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，这可能使它独一无二，那就是在它漫长的存在过程中，在45亿年的时间里，太阳亮度的变化被可变的温室效应抵消了。它就像地球物理的恒温器一样，表面有海洋，使地球始终适宜居住。

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.

但这个恒温器还需要再微调一下，才能让它完美运转，让我们的星球真正适合生命生存。经过数亿年的时间，大气中所有的二氧化碳都可能以海洋底部钙质岩石的形式被封存。

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.

没有足够的循环来保持恒温器运转的话它就会坏掉。一种可能是地球独有的机制允许二氧化碳重新注入大气之中：板块构造。

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.

你必须认识到，地球有一种由冰冷而坚硬的岩石构成的外壳。其内部有更温暖的岩石——地幔，它会改变形状。

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

这一层更柔软一些。所以你可以想象成地壳形成了一个坚实的完整的外壳，就像蛋壳包裹着更软的内部一样。

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.

但这还不对。内部移动的岩石的运动非常强大，足以摩擦地壳并使其碎裂。

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.

地球的地壳裂成了十个板块，这些板块由于地幔的运动而移位。在板块接触的地方，它们互相挤压，将海底的岩石拖到地球深处。

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.

二氧化碳的回收就这样开始了。在巨大的压力和热量下，岩石融化，岩浆喷出地表，二氧化碳也随之喷出。

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.

在火山爆发时，二氧化碳以气体形式逃逸。最后回到大气中，二氧化碳可能会被海洋再次捕获，也可能不会，这取决于气候条件。

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.

这个循环完成了。它是一个非常特殊的地球物理恒温器，我们认为它真的控制了地球上的气候条件，让生命成为可能。

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.

如果你稍微改变一下板块构造，有稍微多于或少于十个板块，那么循环和二氧化碳的浓度就会有所不同，生物圈也会有不同的进化。这引出了另一个重要的问题。

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?

这种板块构造似乎就是关键所在，似乎是地球生命的关键……板块构造在银河系的其他地方真的很普遍吗？还是在地球独一无二或非常罕见？

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.

在太阳系中，你在其他任何地方都找不到它。板块构造可能是地球的邻近行星没有生命出现和生存的因素。

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，太阳系的其他岩石行星中的一颗确实有了一个良好的开端。在火星早期的历史上，有火山、二氧化碳和水，火星曾享受过与地球相似的环境。

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

所以当时是有这么一个环境的。想象一个有湖泊和河流的蓝色火星。

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

有些人认为在火星的北半球有海洋。所以这是一个有利于生命存在的环境。

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.

这一切似乎都是为地球以类似的方式运行而设置的。然而，这颗红色星球目前的状态清楚地表明，有什么问题出现了。

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.

火星冷却得更快。由于火星是地球的一半大小，这有点像把一大壶热水与一杯茶作比较。

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

大壶的热水比小杯的茶冷却得慢，后者即指火星。其内部冷却得更快。

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，按照我们的理解，板块构造是不可能产生的。没有什么再循环可以维持几十亿年对海洋有利的气候。

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

火星存在了数亿年。从那以后，它就变成了一个贫瘠的星球。

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.

火星的悲剧在于它太小了，而且陷入了致命的漩涡。由于它的质量较小，没有足够的重力来抓住它的大气层，大气压力的下降就是不可避免的，太阳风把它们都吹走了。

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

一些水蒸发了，其余的结冰了。蓝色火星变成了红色火星，成为了自身体积小的牺牲品。

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，地球的大小就正合适！那么，为什么和地球一样大小的金星上没有板块构造运动呢？

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

这是为什么？与地球不同的是，金星几乎没有水。

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.

所有的水都没了，地幔非常干燥，不润滑。它不能大幅移动或移动表面上的任何板块。

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

所以金星在行星周围有一层完整的外壳。它没有地球的运作机制。

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.

所以不仅仅要大小合适，地幔中有水也很重要。地球有足够的水来润滑它的板块构造运动。

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

金星则没有。然而，这两颗行星是由相同的物质构成的。

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

地球年轻时发生的一件非常特殊的事件可能使它深度水化。是这样的。

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.

为了让地幔得到足够的水分和润滑，地球在其存在的早期经历了巨大的灾难。我们认为年轻的地球被另一颗火星大小的行星撞击了，我们称之为忒伊亚。

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.

地球诞生后几千万年，经历了一场大灾难，几乎将它完全摧毁。太阳系起源的混乱仍然存在。

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

想象一下，围绕着地球，有数百颗卫星或数十颗火星。它们不断的碰撞，这些物体成长并形成行星。

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，一个火星大小的物体朝地球飞来，并以大约每秒15公里的速度撞向地球表面。忒伊亚撞上了地球。

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.

这次巨大碰撞释放的能量相当于数千亿颗氢弹。撞击如此猛烈以致于撞击物都被摧毁了。

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，撞击体的核穿透地幔，成为地核的一部分。我们认为地核与撞击体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.

这次碰撞是如此猛烈，以至于忒伊亚所含的水被打入地核深处，与已经存在的水混合在了一起。通过这种方式，忒伊亚将地球地幔的深处水化，使得后来的板块构造系统能够发挥作用。

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.

这是推测性运动的，但如果它是正确的，就十分令人惊讶了。它告诉我们，要想在地球上一直存在有生命，我们就需要在地球历史的早期有这种偶然的撞击，使地幔水化，保持其润滑，并使这种现象，这种地球物理恒温器，贯穿整个地球的存在。

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.

随着地球获得了一个新伙伴，这个表面上的灾难最终会以另一种方式带来好处，它将在我们生态系统的繁盛中发挥重要作用。在碰撞产生的碎片云中，一个新的物体会逐渐形成。

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。地月系统在太阳系中是独一无二的，到目前为止，在银河系中也是独一无二的。

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

这是一个非常特殊的系统，两个物体都是大物体。这就是某些天文学家称之为“双行星”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.

月球还没有形成，就已经因其巨大的体积对地球产生了强大的影响。由于阿波罗计划，地月关系的历史已经被非常仔细地进行了研究。

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.

阿波罗计划在月球表面安装了反射器。这些反射器现在被用来反射从地球发射的激光束，比如我身后的这个。

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.

这里有一个定期的发射，法国的卡伦高原。今天，世界各地的许多天文台，比如位于上普罗旺斯阿尔卑斯的这个天文台，都在密切监测月球。

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，科学家们都会用激光束精确测量它与地球的距离。这些实验很重要，因为我们可以测量激光束往返月球所需的时间。

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.

所以我们就可以实时测量到月球的距离。一个主要的发现是，月球正在远离地球，这是我们以前知道的，但现在可以确定的。

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厘米的速度向远离去。这些测量结果表明，月球形成时与地球的距离要比现在近得多。

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.

月球形成后不久，如果有人来这里看月亮的话，它在天空中一定是巨大的，因为它离我们很近。现在它距离地球有38万公里。

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40亿年前，我们认为这个距离只有15000公里远。月球靠近地球的第一个后果是造成更大的潮汐，因此可能会刺激生物进化。

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.

由月球引起的潮汐搅动海洋，促进了我们生态系统的活力。两个物体之间的相互吸引对地球的旋转轴也有至关重要的影响。

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.

影响不仅仅是带来潮汐，还有更多。它稳定了著名的倾斜角度(23度，地轴相对于绕太阳轨道倾斜)。

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.

这个角度数十亿年来都保持不变。如果月球没有在那里，地球的转轴就会振荡，导致气候的迅速变化。

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

这可能对进化产生了巨大的影响。例如冰川作用和气候变暖的快速交替时期。

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.

月球帮助地球维持了足够稳定的气候，使生命得以缓慢而渐进地进化。如果没有月球，地球将面临与它的邻居火星一样的剧变。

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、火卫一和火卫二的卫星都太小了，它们在转轴上起不到稳定作用。火星的转轴有很大的变化。

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，这个旋转轴绕着火星表面转动。火星变成了沙漠；地球，则是一座伊甸园。

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.

目前的地月系统是一系列意外事件的结果，使地球和月球成为独一无二的一对。地球现在有了稳定的气候、大气和液态水。

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

毫无疑问，一切都为生命的出现和进化做好了完美的准备。但是地球仍然缺乏生命的基本成分：有机分子。

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构件组成的：长碳基分子。科学家们现在认为，这些分子中的很大一部分来自地球以外的行星。

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

有机分子是生命所必需的基本元素，是在太空中被发现的。他们在陨星之中。

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

其中一些含有60%的有机物质，这是一个巨大的数字。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?

最初的有机分子可能在地球上播下了生命的种子，它们存在于太阳系遥远的寒冷地带。但是这些生命的组成部分是如何到达我们的星球的呢？

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.

罗塞塔任务是首次尝试在彗星上着陆太空舱，这为解开这个谜团提供了一些线索。让-皮埃尔·比普林(Jean-Pierre Bipring)是推动这项大胆任务背后的科学家之一。

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."

这是我们在2014年7月14日看到的。当我们得到这个的时候，我们想着：“我们不能在上面着陆，这是不可行的。”

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

这太小了。整个星球只有4公里，而且它绕着一个很尴尬的轴旋转。

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.

我们以为我们永远找不到落脚的地方，这太疯狂了。几个月后，尽管困难重重，“菲莱”号探测器还是成功降落在了“丘里”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.

这里你可以看到菲莱的支架，它是几年前制造的，这里是太阳系中最古老的物体，保持着和46亿年前形成时相同的模样。这是我们第一次在彗星上放置东西，而且不会很快再次发生。

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.

通过最初的分析，科学家们意识到彗星与他们所认为的非常不同。这颗彗星表面没有水。

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

连一盎司的冰都没有。我们原以为它主要是冰，只有一些分子微粒。

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

根本不是这样。我们在这里看到的都是有机物。

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.

多亏了罗塞塔号任务，科学家们发现彗星是构成生命的重要组成部分。在此之前，他们一直认为只有小行星，岩石小天体，才有这样的天赋。

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.

自从太阳系诞生以来，彗星和小行星就一直被吸引到较冷的区域，在那里它们捕获并储存了这些原始的有机分子。然后这些彗星和小行星，真正的生命信使，把这些分子运送到太阳系的内部区域。

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.

当它们接近一颗行星时，它们会把这些组成部分散布到行星表面，为行星提供生命所需的物资。科学家们热衷于对有机分子进行实验室分析，即类似于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.

这就是由日本航天局发射的隼鸟2号任务的目标：将这些原始有机物的一些碎片带回地球。该样本于2019年7月在距离地球3亿公里的地方采集。

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

这次任务取得了成功。这就是飞行器降落的时刻。

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

你看到那个支架着地了。这令人十分兴奋。

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

然后你看到它再次起飞。采集样本的原则是不要逗留太久。

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

它着陆后发射了一颗子弹，然后带着那些碎片再次离开。这只花了几秒钟的时间。

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

当然，这一切都发生在离地球很远的地方。这真的是令人超级兴奋。

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.

我们希望样本中含有碳质物质，我们认为地球上的生命是从碳质物质开始的。探测器带回了十分之一克珍贵的构成生命的物质，类似于40亿年前降落在太阳系行星上的物质。

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.

从这些材料中，我们想找出最初的成分是什么，是什么在地球原始海洋的水中，使陆地生物伟大链条的形成成为可能。彗星和小行星可能是长链中缺失的一环。

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.

这条链从早期云尘中发现的简单分子开始，最终形成了地球上生命最初起源的构成要素。是一条通往生命的长链。

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