Clara Sousa-Silva: The fingerprints of life beyond Earth | TED

譯者: Sichen Wei 審譯者: Helen Chang

It's my job to find aliens, so as you might guess,

我的工作是尋找外星人。

因此你可能會猜

I spent a lot of time thinking about them,

我花很多時間思考他們，

imagining little green women

想像小綠人，

meeting up with their friends, commuting to work.

和他們的朋友相聚，通勤工作。

And that gets me thinking about alien astronomers

這使我想到了外星天文學家

trying to find us in their night sky.

是否也試圖在夜空中尋找我們。

If these alien astronomers had looked in our direction

如果這些外星天文學家

在上個世紀看向了我們這裡，

in the last century,

they would have been really excited to detect unequivocal signs of technology.

他們會因為探測到一些 明確的科技跡象而非常興奮。

But what if they looked ten thousand years ago,

但是如果他們在幾千年前， 在我們展示任何文明跡象之前，

before we showed signs of civilization?

就看向了我們這裡會怎麼樣呢？

Would they shrug in disappointment and go look elsewhere for life?

他們會失望的聳聳肩， 然後去尋找別的地方的生命嗎？

No, and neither should we.

他們不會，我們也不應該如此。

Instead, we can look for other signs of life.

相反，我們會尋找 其他預示著生命的跡象。

For example, if those alien astronomers had looked our way 10,000 years ago,

舉個例子，如果外星天文學家 已經在一萬年以前看向我們，

they might notice that even without signs of civilization,

他們也許注意到 儘管沒有任何文明的跡象，

we still looked slightly unusual.

我們仍然看起來有一點不尋常。

For one, we have a thick and temperate atmosphere,

其一，我們有很厚的大氣 和溫和的氣候，

but more notably,

但更值得注意的是，

we have suspiciously large amounts of oxygen in the atmosphere.

我們的大氣中有大量到可疑的氧氣。

This would be a really encouraging sign of life for my alien colleagues

這將是一個對我的外星同事 非常鼓舞人心的生命跡象，

because the composition of the Earth's atmosphere

因為地球大氣的組成

can only sustain itself through a biological cycle.

只能通過生物循環維持自身。

So can we do the same to them?

那麼我能們對他們做同樣探測嗎？

I'm certainly trying.

我無疑在努力嘗試。

I am a quantum astrochemist,

我是一名量子天文學家，

which means I study the quantum interactions

這意味著我研究 太空中分子與光相互作用。

between molecules and light in space.

We can't see these molecules or even the planets they're on.

我們看不到那些分子， 甚至看不到它們所在的星球。

But when life from a star goes through an alien atmosphere,

但當生命穿過外星大氣時，

each molecule within it leaves a unique fingerprint

上面的每一個分子 都會在星光中留下獨特的痕跡，

in the starlight that I can see from here.

所以在星光下，我們可以看到。

And I look for the fingerprints

我尋找這些與生命相關的

of molecules that could be associated with life,

存在於分子上的痕跡

or biosignatures,

或者是生物印記，

like complex pollutants or oxygen.

像是結構複雜的污染物或是氧氣。

In the context of Earth, oxygen is a wonderful biosignature,

在地球，氧氣是一個完美的生物印記，

but oxygen is not that hard to make.

但是氧氣並不難製造。

So, for example, if our sun had different levels of radiation

幾個例子，如果我們的太陽 有不同的輻射值

or if our oceans were evaporating from a runaway greenhouse effect,

或者我們的海洋 因為失控的溫室效應而蒸發，

then large amounts of oxygen could accumulate in our atmosphere

大量的氧氣能夠在我們沒有生物的

without biology,

大氣中聚集，

and then oxygen would be a false positive for life.

那樣的話，氧氣就是一個 這裡有生命存在的誤報。

So maybe oxygen won't be the solution to finding life beyond Earth,

所以或許氧氣不是判斷 地球外是否有生命的一個有效方法。

but then what is?

那什麼才是呢？

Well, my specialty is to look for unusual molecules

我的專長是尋找不尋常的分子，

that have fewer false positives for life

視它們為生命跡象罕為誤報，

because they're so difficult to make that they're rarely made spontaneously.

因為它們很難產生，很難自發產生。

And my favorite of those unusual molecules is phosphine.

我最喜歡的不尋常分子是膦。

When I first started working on phosphine about a decade ago,

大約十年前我第一次研究膦時，

people had a hard time thinking of it as a biosignature at all.

人們很難把它視為生物標記物。

Instead, it was known

而是視它為

for being this horrific, foul-smelling molecule

眾所週知可怕又無比難聞的分子，

that messes with life's ability to use oxygen,

會擾亂生命使用氧氣的能力，

making it a really effective killer.

使其成為真正有效的致死物。

Because of this fatal interaction with oxygen metabolism,

有著這種與氧氣相互作用的致命反應，

phosphine is used widely as a pesticide

膦被廣泛用於殺蟲劑。

and sadly for the same reason it was used many times in chemical warfare.

不幸的是，也正是因為這個原因 它被多次用於化學武器。

Phosphine can be made in the lab,

膦可以在實驗室製作出來，

and it's also produced in the extreme environments

同時也能夠在極端環境下產生。

found inside gas giants like Jupiter and Saturn.

在木星和土星這些 大型的氣體行星中找得到。

But on rocky planets like the Earth, it is rarely created accidentally.

像地球這樣多岩石的星球 就很難意外地產生。

So we don't really expect to find phosphine on Earth at all.

所以我們其實完全不期待 在地球上找到膦。

And yet we do.

然而我們發現了。

We find it in small amounts throughout the globe,

我們在全球範圍內 找到了少量的膦，

and in some places in strangely large quantities,

而在有些地方，數量驚人。

places like swamps and rice fields and lake beds

比如在沼澤地、稻田和湖床，

and the excrements and guts of most animals.

還存在於大多數動物的 排泄物和內臟裡。

And what all of these ecosystems have in common

這些生態系統的共同點是

is that they all host organisms that are not reliant on oxygen,

它們都是不依賴氧氣的宿主，

so phosphine can't hurt them.

所以膦不能傷害它們分毫。

Indeed, phosphine seems to be safely and enthusiastically produced

確實，看似膦在這些 氧氣稀薄的生態環境中

in all of these oxygen-poor ecosystems.

安穩且肆無忌憚地被製造出來。

So I figured, maybe other planets with life less reliant on oxygen than ours

所以我想，也許其他行星有生命 對氧氣的依賴程度比我們的低

could also have phosphine, but as a really popular biosignature.

也會有膦，可當作普及的生物印記。

And here's the best thing about phosphine.

這是關於膦最好的地方。

Because it's so hard to make on rocky planets like the Earth,

因為它很難產生於地球 這種多岩石的星球，

it has almost no false positives for life.

它幾乎不可能誤報為有生命跡象。

So I started considering what telescopes we would need

所以我開始考慮 我們需要用什麼樣的望遠鏡

to detect phosphine on planets in our galactic neighborhood.

檢測我們銀河系附近行星上的膦。

Because if we did, I predicted it could only mean life.

因為一旦探測到了， 我預測它就意味著生命跡象。

I was imagining a distant planet,

我想像着某個遠方的星球，

a oxygen-poor tropical paradise

它是氧氣稀薄的熱帶天堂，

with a phosphine-rich biosphere that we might one day be able to detect.

有着富含膦的生物圈 有朝一日會被發現。

But turns out phosphine was a little more exciting

結果膦比我最初設想的更令人興奮。

than I had initially envisaged

because a few months after I finished this work

就在我結束這項工作幾個月之後，

an astronomer, Jane Greaves, reached out to me

天文學家簡·格里夫斯向我尋求幫助

asking for help with interpreting a telescope signal seen here in white.

解讀這些以望遠鏡看到的 用白色顯示的信號。

Then months later, another signal, seen here in orange,

幾個月後，解讀另一個信號， 在這裡以橙色顯示，

that seemed to indicate that phosphine might be present not on a distant planet,

似乎意味著膦可能就出現在 離我們不遠的星球，

but right next door, on the clouds of Venus.

就在我們隔壁，金星的雲層上。

So did we do it?

那麼，我們成功了嗎？

Did we find life beyond Earth? We don't know.

我們在地球之外找到生命了嗎？ 我們還不知道。

These Venus observations were noisy and preliminary,

這些對於金星的觀察 是初步的、有干擾的，

so we still need to confirm, without a doubt,

所以我們仍然需要再去確認， 但無庸置疑的是，

that the signal is real,

信號是真實的。

and if it is, we need to make sure

如果它是真的，我們需要確保

it's not another molecule mimicking phosphine's fingerprint.

那不是其它分子 在模仿膦留下的痕跡。

And if it is unambiguously phosphine,

如果它毫無疑問是膦，

we still need to figure out what or who is making it,

我們還需要弄清楚 是什麼或是誰製造了它。

because maybe it's true

因為可能真是如此，

that life is the best explanation for the presence of phosphine

有生命存在是膦出現於 金星之類的星球是最好的解釋。

on a planet like Venus.

But maybe that's wrong

也可能是錯的，

and there's an exotic but not biological way of making phosphine

還有一種前人未曾想過的、 不尋常的、非生物的產生途徑。

that no one has thought of yet.

Either way, as much as I love phosphine,

不管怎樣，儘管我這麼喜歡膦，

I don't think that's how we'll find life.

我不認為這樣就可以找到外太空生命。

The detection of life will likely not come from a single molecule.

探測到生命不會僅憑一種分子。

No matter how special it is.

無論它多麼特殊。

We'll have to detect a whole biosphere producing a complex network of gases

我們必須探測整個生物圈產生的 複雜氣體網絡，

that together form a message that reads: “We’re alive!”

它們一起形成了一條信息， 解讀為：「我們活著！」

As the Venus story shows,

正如金星所顯現的那樣，

the detection of life will likely be uncertain,

探測生命跡象有可能是不確定的，

but Venus is the perfect lab for us to test our theories of biospheres

但金星是個完美的實驗室， 用來測試我們的生物圈理論

and how to interpret them.

以及如何解釋它們。

If we learn to understand the atmosphere of Venus

如果我們掌握和理解金星的大氣環境

and the message it contains,

和其中蘊含的信息，

then we can find out if we got it right by going there and checking.

之後就可以去那裡實地勘察 我們的判斷是否正確。

And we'll do that at the end of the decade.

我們將在十年後辦得到。

But this will not be the last time

這絕不會是我們最後一次

that we have the discovery of a biosignature

在一個潛在宜居的星球上 發現生命印記，

on a potentially habitable planet,

and next time we won't be able to just go there and check.

下次我們將無法去那裡檢查。

So my biggest concern

所以我最擔心的

is not that we will fail to find a habitable planet in our lifetimes.

並不是我們在有生之年 找不到宜居的星球，

My biggest concern is that we'll point our very expensive telescopes

而是擔心我們用造價不菲的望遠鏡

directly at an inhabited planet

對準了一顆宜居的星球，

and just not know we did it.

卻渾然不知。

But I am determined to not miss life.

但我決心不錯過任何可以找到的生命。

So, yes, I will look for the unambiguous but quite unlikely signs of technology

所以，沒錯，我會繼續尋找 明確但不太可能的技術跡象，

like complex pollutants.

像是結構複雜的污染物。

And I'll look for the pleasant and familiar

我會繼續尋找讓人愉快又熟悉，

but potentially misleading signs of life, like oxygen.

但可能被誤解的生物信號，像是氧氣。

And of course, I'll keep looking

當然，我還會繼續尋找

for the strange and scary biosignatures like phosphine.

像膦一樣奇怪又可怕的生物印記。

But crucially, I will look for all the molecules

此外至關重要的是， 我會繼續尋找所有可以

that can together paint a holistic picture of a biosphere.

一起描繪出生物圈整體風貌的分子。

All of this so that one day we'll know life when we see it.

所有這一切都是為了有一天 當我們看到生命時，就知道是它。

Thank you.

謝謝。