There may be extraterrestrial life in our solar system - Augusto Carballido

譯者: Lilian Chiu 審譯者: Carol Wang

Deep in our solar system,

在我們的太陽系深處，

a new era of space exploration is unfolding.

太空探索的新世紀正在展開。

Beneath the thick ice of Europa,

在木衛二的厚冰底下，

in the vapor plumes on Enceladus,

在土衛二的噴射羽流中，

and within the methane lakes of Titan,

在土衛六的甲烷湖中，

astrobiologists are on the hunt for extraterrestrial life.

都是天體生物學家找尋 外太空生命的探索目標。

We’ve honed in on these three moons because each is an ‘ocean world,’

我們專注在這三個衞星上，因為 它們各自都是一個「海洋世界」，

an environment that contains a liquid ocean–

即含有液體海洋的環境——

and liquid can support the formation of life.

液體可以支持生命的形成。

Living organisms have to be able to grow, reproduce, and feed themselves,

有生命的有機體必須要能夠

成長、生殖、攝取食物等等。

among other things.

All of those functions require the formation of complex molecules

所有這些功能， 都需要用比較基礎的成分

from more basic components.

來形成複雜的分子。

Liquids such as water allow chemical compounds to remain in suspension

如水這類液體， 能讓化合物保持懸浮，

instead of sinking under the force of gravity.

而不會因為重力而下沉。

This enables them to interact frequently in a 3-dimensional space and,

因此，它們就能夠 在三度空間中頻繁交互作用，

而且在對的條件下，

in the right conditions,

go through chemical reactions that lead to the formation of living matter.

就會發生化學反應而形成活的物質。

That alone isn’t enough;

光這樣還不夠；

the small but complex biomolecules that we’re familiar with

我們很熟悉微小但複雜的生物分子，

are sensitive to temperature—

它們對於溫度很敏感——

too hot or cold, and they won’t mix.

太熱或太冷時不會混合。

Liquid water has an additional advantage

液態水有一項額外的好處，

in that it’s relatively temperature-stable,

就是它的溫度相對來説很穩定，

meaning it can insulate molecules against large shifts in heat.

意即，它能將分子 與巨大熱能變化隔離開來。

On Earth, these and other conditions in aquatic environments

在地球上，在水環境中的 這些條件和其他條件，

may have supported the emergence of life billions of years ago.

在數十億年前可能 就支持了生命的出現。

Tantalizingly, the same could be true in other parts of our solar system,

吊人胃口的是，

在我們的太陽系其他地方， 同樣的事也可能會發生，

like these three icy moons.

比如上述的三個覆冰衛星。

Europa, which is a moon of Jupiter,

木衞二是木星的衛星，

is probably the most intriguing ocean world.

可能是最讓人感興趣的海洋世界。

Beneath a surface layer of ice thicker than Mount Everest,

在比聖母峰還要厚的表層冰底下，

there exists a liquid ocean as much as 100 kilometers deep.

有一片液態海洋， 足足有一百公里深。

Astrobiologists think this hidden ocean could harbor life.

天體生物學家認為這片 隱藏的海洋中可能藏有生命。

Thanks to the Galileo probe,

因為有伽利略號探測器，

we can deduce that its potential salt content

我們可以推論，它可能含有鹽份，

is similar to that of some lakes on Earth.

且這些鹽份和地球上的 一些湖泊很類似。

But most of its characteristics will be a mystery until we can explore it further.

但在我們能進一步 探索它之前仍然成謎。

Like Jupiter, Saturn also has moons that might have the right conditions for life.

和木星一樣，土星的衛星上 可能也有適合生命的正確條件。

For instance– Enceladus is a tiny ball of ice that’s small enough to nestle

比如——土衛二是個小冰球，

小到足以放入墨西哥灣的 表面區域之中。

within the surface area of the Gulf of Mexico.

Similarly to Europa, it likely contains an ocean deep under the ice.

與木衛二類似，土衛二的冰下 深處很可能也有一個海洋。

But Enceladus also has geysers

但土衛二有噴泉，

that frequently vent water vapor and tiny ice grains into space.

經常會排放水氣和小冰塊到太空中。

Astrobiologists are curious about whether these geysers

天體生物學家很好奇這些噴泉

是否和底下的海洋連結。

are connected to the ocean below.

They hope to send a probe to test whether the geysers’ plumes of vapor

他們希望能派出探測飛船， 以檢測噴泉的噴流

contain life-enabling material from that hidden sea.

是否含有來自那隱藏海洋的 能促成生命的物質。

Although it’s the best known substance for nurturing life,

雖然水是已知最能滋養生命的物質，

water isn’t necessarily the only medium that can support living things.

但未必是唯一支持生命存在的媒介。

Take Titan, Saturn’s largest moon,

以土星最大的衛星土衛六為例，

which has a thick nitrogen atmosphere

它有很厚的氮大氣層，

containing methane and many other organic molecules.

含有甲烷和許多其他有機分子。

Its clouds condense and rain onto Titan’s surface,

它的雲會凝結形成降雨 落到土衛六的表面，

sustaining lakes and seas full of liquid methane.

讓湖泊和海洋能維持 滿滿的液態甲烷。

This compound’s particular chemistry means it’s not as supportive a medium as water.

這種化合物的特殊化學性質 導致它不像水那麼能支撐生命。

But, paired with the high quantities of organic material

但若能搭配

同樣從天而降的大量有機物質，

that also rain down from the sky,

these bodies of liquid methane could possibly support unfamiliar life forms.

這些液態甲烷體有可能支持 我們不熟悉的生命形式。

So what might indicate that life exists on these or other worlds?

所以，什麼跡象能表示在這些世界 或其他世界中有生命存在？

If it is out there, astrobiologists speculate that it would be microscopic,

若太空中有生命，

天體生物學家推測這種生命 也只能用顯微鏡看到，

comparable to the bacteria we have on earth.

就像我們在地球上的細菌。

This would make it difficult to directly observe from a great distance,

這麼一來，從遠距離 就很難直接觀察到，

so astrobiologists seek clues called biosignatures.

所以天體生物學家 在尋求線索，即生物標記。

Those may be cells, fossils, or mineral traces left behind by living things.

生物標記可能是細胞、化石、

或生物留下的礦物痕跡。

And finding any biosignatures will be challenging for many reasons.

找到任何一種生物標記 都很困難，理由有許多。

One of the biggest concerns

最大的考量，

is to make sure we sterilize our probes extremely thoroughly.

是要確保我們徹底消毒探測飛船。

Otherwise we could accidentally contaminate ocean worlds

要不然，我們可能會 不小心用地球的細菌

with Earth’s own bacteria,

污染了海洋世界，

which could destroy alien life.

導致外星生命死亡。

Titan, Enceladus, and Europa

有許多我們可能 可以探索的海洋世界，

are just three of possibly many ocean worlds that we could explore.

土衛六、土衛二、 木衛二僅是其中的三個。

We already know of several other candidates in our solar system,

我們已經知道，在我們的 太陽系中還有數個候選者，

including Jupiter’s moons Callisto and Ganymede,

包括木星的衛星： 木衛四和木衛三，

Neptune’s Triton, and even Pluto.

海王星的海衛一，甚至冥王星。

If there’s this much potential for life to exist in our own tiny solar system,

如果在我們小小的太陽系中 就有這麼多生命的可能性，

what unimagined secrets might the rest of the universe contain?

在宇宙的其他地方， 會有多麼難以想像的秘密？