Nathalie Cabrol: How Mars might hold the secret to the origin of life

譯者: FBC GLOBAL 審譯者: Coco Shen

Well, you know, sometimes

古語有云：

the most important things come in the smallest packages.

合抱之木，生于毫末； 九層之台，起于壘土。

I am going to try to convince you, in the 15 minutes I have,

接下來的一刻鐘裏， 大家會發現

that microbes have a lot to say about questions such as,

微生物世界暗藏玄機，

"Are we alone?"

有可能幫助解開 人類身世的謎題。

and they can tell us more about not only life in our solar system

對微生物世界的探索，

but also maybe beyond,

還將開拓我們對太陽系 及系外生命的認知。

and this is why I am tracking them down in the most impossible places on Earth,

正是懷著這樣的信念， 我不辭艱辛，

in extreme environments where conditions

遠赴地球一隅追尋 微生物的足跡，

are really pushing them to the brink of survival.

見證它們在極端環境下 的生存狀態。

Actually, sometimes me too, when I'm trying to follow them too close.

環境之惡劣與嚴峻， 令我自己都望而却步。

But here's the thing:

普遍認同的觀點是，

We are the only advanced civilization in the solar system,

雖然人類社會是太陽系 唯一的高等文明，

but that doesn't mean that there is no microbial life nearby.

但並不意味著， 附近星系沒有微生物存在。

In fact, the planets and moons you see here

像這些行星及其衛星

could host life -- all of them -- and we know that,

都有可能是生命的家園，

and it's a strong possibility.

我們對此較爲確信。

And if we were going to find life on those moons and planets,

一旦在這些星球上發現生命，

then we would answer questions such as,

我們也許能回答以下問題：

are we alone in the solar system?

太陽系裏人類是否孑然一身？

Where are we coming from?

我們來自何方？

Do we have family in the neighborhood?

附近星系中是否有我們的親戚？

Is there life beyond our solar system?

太陽系之外是否有生命存在？

And we can ask all those questions because there has been a revolution

諸如此類的問題沒有窮盡，

in our understanding of what a habitable planet is,

因爲對於什麽星球適合生存、居住， 我們的認識一直在變化。

and today, a habitable planet is a planet

時至今日，我們認爲適宜居住的星球

that has a zone where water can stay stable,

應該環繞著大氣圈， 幫助保持水分。

but to me this is a horizontal definition of habitability,

但對我而言，這只是衡量 適宜居住的一個橫軸，

because it involves a distance to a star,

只要與恒星之間存在 合適的距離即可滿足這一要求；

but there is another dimension to habitability,

還需要有一個衡量維度——

and this is a vertical dimension.

縱軸，

Think of it as

借此衡量地表以下的生存條件。

conditions in the subsurface of a planet where you are very far away from a sun,

地表之下遠離太陽，

but you still have water, energy, nutrients,

生命仍然需要水分、能量 和營養來維持，

which for some of them means food,

對於一些生命而言，

and a protection.

這是指食物和庇護之所。

And when you look at the Earth,

比如我們的地球，

very far away from any sunlight, deep in the ocean,

在遠離光照的深海之底，

you have life thriving

依然萬物繁衍，生生不息。

and it uses only chemistry for life processes.

生命進程全仰賴化學作用。

So when you think of it at that point, all walls collapse.

從這個角度來審視生命，

You have no limitations, basically.

我們獲得了開闊的視界。

And if you have been looking at the headlines lately,

如果各位關注科學界的重大新聞，

then you will see that we have discovered a subsurface ocean

應該知道我們最近

on Europa, on Ganymede, on Enceladus, on Titan,

在木衛二、木衛三、土衛二和 土衛六上發現了次表層海洋，

and now we are finding a geyser and hot springs on Enceladus,

又在土衛二上找到了間歇泉和溫泉。

Our solar system is turning into a giant spa.

太陽系搖身一變， 似乎成了巨型SPA會所！

For anybody who has gone to a spa knows how much microbes like that, right?

SPA會所裏有多少微生物？ 各位曾光顧會所的人有切身體會。

(Laughter)

（笑聲）

So at that point, think also about Mars.

我們再來看看火星的情况。

There is no life possible at the surface of Mars today,

在火星表面尚未發現生命，

but it might still be hiding underground.

但生命有可能隱藏於地表之下。

So, we have been making progress in our understanding of habitability,

我們對“適宜居住”的概念 有了更深的認識，

but we also have been making progress in our understanding

同時對地球上的生命信號

of what the signatures of life are on Earth.

也有新的瞭解。

And you can have what we call organic molecules,

這些生命信號包括有機分子，

and these are the bricks of life,

它是構成生命的基本材料；

and you can have fossils,

還包括化石、

and you can minerals, biominerals,

礦物，以及生物礦物——

which is due to the reaction between bacteria and rocks,

這是細菌與岩石反應的産物；

and of course you can have gases in the atmosphere.

大氣中的各類氣體當然 也是生命信號之一。

And when you look at those tiny green algae

請看畫面右側，

on the right of the slide here,

這些微小的綠藻，

they are the direct descendants of those who have been pumping oxygen

正是十億年前

a billion years ago in the atmosphere of the Earth.

向地球大氣層釋放氧氣 的原始藻類植物的後裔。

When they did that, they poisoned 90 percent of the life

在釋放大量氧氣的同時，

at the surface of the Earth,

它們毒殺了地球表面90%的生命，

but they are the reason why you are breathing this air today.

這些生命的消失 成全了人類的今天。

But as much as our understanding grows of all of these things,

儘管我們的知識與日俱增，

there is one question we still cannot answer,

但仍然無法回答一個問題：

and this is, where are we coming from?

我們來自何方？

And you know, it's getting worse,

而且，回答問題的難度 似乎在增加——

because we won't be able to find the physical evidence

因爲我們無法找到實物證據

of where we are coming from on this planet,

證明我們來自地球何處。

and the reason being is that anything that is older than four billion years is gone.

四十億年前的所有證據 已蕩然無存，

All record is gone,

各種記錄都銷聲匿跡，

erased by plate tectonics and erosion.

在板塊構造和氣候 變遷中湮滅無痕。

This is what I call the Earth's biological horizon.

我把這種未知的生命源頭 稱作“生物地平綫”，

Beyond this horizon we don't know where we are coming from.

生命來自地平綫之外的何處， 我們一無所知。

So is everything lost? Well, maybe not.

是否尚存蛛絲馬跡？也許。

And we might be able to find evidence of our own origin

我們也許有可能在火星

in the most unlikely place, and this place in Mars.

這個最不可能的地方， 發現人類起源的證據。

How is this possible?

爲什麽呢？

Well clearly at the beginning of the solar system,

在太陽系形成之初， 火星和地球

Mars and the Earth were bombarded by giant asteroids and comets,

都遭受了小行星和彗星的猛烈撞擊，

and there were ejecta from these impacts all over the place.

撞擊造成碎片四處飛濺。

Earth and Mars kept throwing rocks at each other for a very long time.

地球與火星相互投擲石塊， “戰况”不斷。

Pieces of rocks landed on the Earth.

大量巨石襲擊了地球，

Pieces of the Earth landed on Mars.

同時也有來自地球的巨石落入火星。

So clearly, those two planets may have been seeded by the same material.

所以，兩個行星可能包含著孕育 生命的相同物質，

So yeah, maybe Granddady is sitting there on the surface and waiting for us.

火星表面也許埋藏著 我們原始祖先的秘密。

But that also means that we can go to Mars and try to find traces of our own origin.

爲此，我們有必要啓程去火星，

Mars may hold that secret for us.

尋找生命之源， 解開身世之謎。

This is why Mars is so special to us.

火星對人類的意義十分特殊。

But for that to happen,

如果火星當時存在生命，

Mars needed to be habitable at the time when conditions were right.

它必定是適宜居住的星球。

So was Mars habitable?

火星當時是否適宜居住呢？

We have a number of missions telling us exactly the same thing today.

多項科研探索證實了同一事實：

At the time when life appeared on the Earth,

地球上最初出現生命的時候，

Mars did have an ocean, it had volcanoes, it had lakes,

火星上存在海洋、火山和湖泊，

and it had deltas like the beautiful picture you see here.

甚至還有如此美麗的三角洲。

This picture was sent by the Curiosity rover only a few weeks ago.

這張照片由“好奇號”火星探測車 於幾個星期前發回，

It shows the remnants of a delta, and this picture tells us something:

顯示了三角洲地區的遺迹， 並告訴我們

water was abundant

火星在相當長一段時間內，

and stayed founting at the surface for a very long time.

湖泊密布，江河奔流——

This is good news for life.

無疑都是孕育生命的溫床。

Life chemistry takes a long time to actually happen.

生命的進化過程步履蹣跚， 曠日持久，

So this is extremely good news,

這對于我們研究生命有利。

but does that mean that if we go there, life will be easy to find on Mars?

但我們去到火星之後， 是否就能輕易找到生命呢？

Not necessarily.

未必。

Here's what happened:

讓我們簡單回顧 火星經歷的劇變。

At the time when life exploded at the surface of the Earth,

當地球上的生命蓬勃發展時，

then everything went south for Mars,

火星則每况愈下，

literally.

日暮途窮。

The atmosphere was stripped away by solar winds,

火星的大氣層被太陽風席捲而去，

Mars lost its magnetosphere,

磁層破壞殆盡，

and then cosmic rays and U.V. bombarded the surface

宇宙射綫和紫外綫長驅直入， 直抵火星地表，

and water escaped to space and went underground.

水分逃逸到太空或滲入地下。

So if we want to be able to understand,

假如我們要瞭解並發現

if we want to be able to find those traces of the signatures of life

火星上的生命信號——

at the surface of Mars, if they are there,

前提是它們的確存在，

we need to understand what was the impact of each of these events

我們需要考慮這一系列變遷

on the preservation of its record.

對火星生命記錄的保存 所産生的影響。

Only then will we be able to know where those signatures are hiding,

只有這樣，我們才能知曉 生命信號的藏身之處，

and only then will we be able to send our rover to the right places

然後驅使火星探測車前往，

where we can sample those rocks that may be telling us something

對岩石等進行採樣、研究，

really important about who we are,

嘗試破解人類的起源之謎；

or, if not, maybe telling us that somewhere, independently,

或者，我們有望發現

life has appeared on another planet.

其他星球存在生命的佐證

So to do that, it's easy.

方法似乎並不困難，

You only need to go back 3.5 billion years ago

我們只需要

in the past of a planet.

穿越到35億年前 的那顆行星。

We just need a time machine.

我們只需要一台時光機，

Easy, right?

對吧？

Well, actually, it is.

完全正確。

Look around you -- that's planet Earth.

請環顧四周， 我們所在的行星地球

This is our time machine.

就是我們的時光機，

Geologists are using it to go back in the past of our own planet.

它載著地質學家回溯 到遠古時代。

I am using it a little bit differently.

但是，我的用法略有不同，

I use planet Earth to go in very extreme environments

我搭乘這台時光機，

where conditions were similar to those of Mars

進入條件類似于當時 火星的極端環境中。

at the time when the climate changed,

當時，火星經歷了氣候劇變，

and there I'm trying to understand what happened.

我嘗試理解這些劇變 所帶來的影響。

What are the signatures of life?

什麼是生命的印記？

What is left? How are we going to find it?

凡走過必留下痕跡？我們要如何追尋？

So for one moment now I'm going to take you with me

現在我就將帶你們

on a trip into that time machine.

穿越時空隧道。

And now, what you see here, we are at 4,500 meters in the Andes,

你可以看到我們已經來到了4,500米之遙的安第斯山脈，

but in fact we are less than a billion years after the Earth and Mars formed.

但事實上這是在地球和火星成型后的近十億年后。

The Earth and Mars will have looked pretty much exactly like that --

那時的地球和火星看起來

volcanoes everywhere, evaporating lakes everywhere,

可能到處都是火山群， 正在蒸發的湖泊隨處可見，

minerals, hot springs,

礦石、溫泉、

and then you see those mounds on the shore of those lakes?

還有在湖岸邊的土丘？

Those are built by the descendants of the first organisms

它們都是由最初構成地球的化石

that gave us the first fossil on Earth.

衍變出的物質組成。

But if we want to understand what's going on, we need to go a little further.

但如果我們希望弄清之後的事，就必須再往前看。

And the other thing about those sites

這些地方的另一景象

is that exactly like on Mars three and a half billion years ago,

和三十五億年前的火星十分相像，

the climate is changing very fast, and water and ice are disappearing.

氣候驟變，你看不到水源和冰川。

But we need to go back to that time when everything changed on Mars,

但我們必須回到火星不穩定的那一刻，

and to do that, we need to go higher.

要這麼做，我們就必須往高處去。

Why is that?

你問為什麼？

Because when you go higher,

因為位置越高，

the atmosphere is getting thinner, it's getting more unstable,

大氣層越細，環境越不穩定，

the temperature is getting cooler, and you have a lot more U.V. radiation.

溫度越來越低，你會受到更多紫外線輻射

Basically,

基本上，

you are getting to those conditions on Mars when everything changed.

對於瞬息萬變的火星來說，這種情況是常有的。

So I was not promising anything about a leisurely trip on the time machine.

所以我不能說這次時光旅行會是次休閒之旅。

You are not going to be sitting in that time machine.

其實當時你並非在搭乘時光機。

You have to haul 1,000 pounds of equipment to the summit

你必須扛著1000磅重的裝備攀上安第斯山脈

of this 20,000-foot volcano in the Andes here.

高達20，000英呎的火山頂峰。

That's about 6,000 meters.

全程距離約為6,000米。

And you also have to sleep on 42-degree slopes

而且你只能在42度的斜坡上就寢

and really hope that there won't be any earthquake that night.

祈禱那晚不會發生地震吧。

But when we get to the summit, we actually find the lake we came for.

但當我們攀上頂峰上，將能親見找尋的湖泊。

At this altitude, this lake is experiencing exactly the same conditions

處於這個高度的湖泊呈現的現狀

as those on Mars three and a half billion years ago.

火星上三十五億前的湖泊無異。

And now we have to change our voyage

現在，我們將更改行程，

into an inner voyage inside that lake,

深入探究那條湖泊的“內涵”，

and to do that, we have to remove our mountain gear

為趕去那，我們必須放棄登山裝備

and actually don suits and go for it.

這些裝備的確是負擔，還是輕裝上陣。

But at the time we enter that lake, at the very moment we enter that lake,

當我們一旦踏入湖泊中，每深入一步，

we are stepping back

就表示我們離重返

three and a half billion years in the past of another planet,

三十五億年前的另一個星球又近了一點，

and then we are going to get the answer came for.

我們已經接近謎底了。

Life is everywhere, absolutely everywhere.

這裡充滿生靈，四處都有生物的氣息。

Everything you see in this picture is a living organism.

你所見的都是鮮活的有機物。

Maybe not so the diver, but everything else.

它們可能不是潛鳥，但確定是某種生物。

But this picture is very deceiving.

眼前的景象令人迷惑。

Life is abundant in those lakes,

這些湖泊中充滿生命體，

but like in many places on Earth right now and due to climate change,

可是和目前地球的某些地區相似，受氣候變化影響

there is a huge loss in biodiversity.

生物多樣性受重創，損失嚴重。

In the samples that we took back home,

我們反觀地球上的取樣結果，

36 percent of the bacteria in those lakes were composed of three species,

這些湖泊中36%的細菌由三種物種組成，

and those three species are the ones that have survived so far.

這三種物種至今仍存活。

Here's another lake, right next to the first one.

相鄰第一條湖旁還有另一條湖。

The red color you see here is not due to minerals.

因礦物質影響湖水已泛紅。

It's actually due to the presence of a tiny algae.

這完全是因為湖水中有微藻。

In this region, the U.V. radiation is really nasty.

該地區的紫外線輻射極其嚴重。

Anywhere on Earth, 11 is considered to be extreme.

縱觀地球，有11個地區堪稱狀況嚴峻。

During U.V. storms there, the U.V. Index reaches 43.

紫紫外線風暴肆虐期間， 這裡的紫外線指數高達43。

SPF 30 is not going to do anything to you over there,

在那裡，防曬指數達30的防曬物品根本不起作用，

and the water is so transparent in those lakes

而湖水卻清澈透明

that the algae has nowhere to hide, really,

微藻清晰可見，

and so they are developing their own sunscreen,

形成天然屏障，

and this is the red color you see.

也就是你所看到的一片鮮紅色。

But they can adapt only so far,

但這不是長久之計，

and then when all the water is gone from the surface,

一旦湖面的湖水乾涸，

microbes have only one solution left:

微生物的生路就只剩下：

They go underground.

轉移至地下。

And those microbes, the rocks you see in that slide here,

而你在另一張幻燈片中看到的微生物、岩石

well, they are actually living inside rocks

都是湖泊中真實存在的岩石

and they are using the protection of the translucence of the rocks

他們利用岩石的半透明性，

to get the good part of the U.V.

吸收紫外線中的有利部分，

and discard the part that could actually damage their DNA.

剔除有損DNA的部分，以達到保護作用。

And this is why we are taking our rover

這也就是我們駕選擇漫步火星

to train them to search for life on Mars in these areas,

探索這些地區生命體的原因，

because if there was life on Mars three and a half billion years ago,

因為如果三十五億年前火星已有生命體存在，

it had to use the same strategy to actually protect itself.

他們必須採用相同的策略進行自我保護。

Now, it is pretty obvious

所以，顯然前往環境條件極端的地區

that going to extreme environments is helping us very much

將極其有助於我們

for the exploration of Mars and to prepare missions.

探索火星，做好準備工作。

So far, it has helped us to understand the geology of Mars.

迄今為止，我們已藉此掌握了 火星的地質情況。

It has helped to understand the past climate of Mars and its evolution,

這有助於了解火星過去的 氣候狀況和演變情況，

but also its habitability potential.

但它仍有適合生物居住的潛力。

Our most recent rover on Mars has discovered traces of organics.

我們近期漫遊火星時已發現了有機物的蹤跡。

Yeah, there are organics at the surface of Mars.

沒錯，火星表面的確有有機物存活。

And it also discovered traces of methane.

我們還發現火星有甲烷存在。

And we don't know yet if the methane in question

我們尚未明確有待驗證的甲烷

is really from geology or biology.

是因地質原因還是生物質原因造成。

Regardless, what we know is that because of the discovery,

無論如何，我們所掌握的是通過探索

the hypothesis that there is still life present on Mars today

對于火星目前仍有生命存在的假設

remains a viable one.

仍然有可能成立。

So by now, I think I have convinced you that Mars is very special to us,

贅述到此，我想我應該能說服 各位火星對於我們有特殊意義，

but it would be a mistake to think that Mars is the only place

但認為火星是太陽系唯一一顆

in the solar system that is interesting to find potential microbial life.

值得探索潛在微生物的星球， 也可能是一種錯誤想法。

And the reason is because Mars and the Earth

這是因為火星和地球

could have a common root to their tree of life,

的生命樹可能是同根同源，

but when you go beyond Mars, it's not that easy.

但如果你跳出火星去看， 並非如此簡單。

Celestial mechanics is not making it so easy

天體力學成為了兩顆星球間

for an exchange of material between planets,

物質轉換的障礙，

and so if we were to discover life on those planets,

所以，如果我們去探索 這些星球的生命體，

it would be different from us.

會發現他們與我們截然不同。

It would be a different type of life.

是兩種不同類的生命體。

But in the end, it might be just us,

但最終，剩下的可能只有我們，

it might be us and Mars,

可能是我們，是火星

or it can be many trees of life in the solar system.

也可能是太陽系中的其它生命樹。

I don't know the answer yet, but I can tell you something:

我無從解答，但我能說的是：

No matter what the result is, no matter what that magic number is,

無論結果如何，無論神秘數字是什麼

it is going to give us a standard

它都為我們衡量我們身處的太陽系以外

by which we are going to be able to measure the life potential,

的生命潛力、充分性

abundance and diversity beyond our own solar system.

和多樣性樹立了標準。

And this can be achieved by our generation.

這有待我們的下一代去完成。

This can be our legacy, but only if we dare to explore.

只有我們勇於探索， 才能為後人留下有價值的東西。

Now, finally,

最後，

if somebody tells you that looking for alien microbes is not cool

如果有人不認為探索 外星微生物很了不起，

because you cannot have a philosophical conversation with them,

因為你無法與他們進行有意義的對話，

let me show you why and how you can tell them they're wrong.

那我將向這些人證明為什麼你們錯了。

Well, organic material is going to tell you

有機物能向你傳達有關環境、

about environment, about complexity and about diversity.

生物複雜性和多樣性的信息。

DNA, or any information carrier, is going to tell you about adaptation,

DNA或各種信息載體能夠讓你了解

about evolution, about survival, about planetary changes

有關適應性、演變、生存、

and about the transfer of information.

行星變化及轉移的信息。

All together, they are telling us

總之，進行這些研究能夠令我們了解

what started as a microbial pathway,

何為微生物路徑的開端，

and why what started as a microbial pathway

為何曾是微生物路徑的開端

sometimes ends up as a civilization

對象有時會成為文明的終結

or sometimes ends up as a dead end.

或最終滅亡。

Look at the solar system, and look at the Earth.

縱觀太陽系和地球。

On Earth, there are many intelligent species,

地球上的物種很多充滿智慧，

but only one has achieved technology.

但僅一種將其變為技術。

Right here in the journey of our own solar system,

我們的太陽系之旅到此階段，

there is a very, very powerful message

已經能獲得強烈的訊息

that says here's how we should look for alien life, small and big.

即我們應該如何從微觀到 宏觀的看待外星生物。

So yeah, microbes are talking and we are listening,

微生物們在發聲， 我們應該精心聆聽，

and they are taking us,

他們將帶領我們

one planet at a time and one moon at a time,

從星球到月球

towards their big brothers out there.

逐步了解他們的其它兄弟。

And they are telling us about diversity,

他們向我們傳達著生物多樣性、

they are telling us about abundance of life,

充分性的信息，

and they are telling us how this life has survived thus far

也讓我們了解到至今形成文明、智能、

to reach civilization,

技術和真正的哲學為止

intelligence, technology and, indeed, philosophy.

生命如何求生存。

Thank you.

謝謝。

(Applause)

（鼓掌）