Why extremophiles bode well for life beyond Earth - Louisa Preston

極端微生物在天體生物學的啟示 - 路易莎．普雷斯頓（Louisa Preston）

譯者: Hao-Wei Chang 審譯者: Kuanju Chou

We've all seen movies

我們都曾看過

about terrible insects from outer space

關於可怕外星蟲族

or stories of abduction by little green men,

或外星人綁架事件的電影

but the study of life in the universe,

但是研究宇宙中的生命

including the possibility of extraterrestrial life,

包含了異星物種的可能性

is also a serious, scientific pursuit.

是一門嚴肅的科學

Astrobiology draws on diverse fields,

天體生物學結合了不同的領域

such as physics,

包含物理

biology,

生物學

astronomy,

天體學

and geology,

和地質學

to study how life was formed on Earth,

用以研究地球上的生命起源

how it could form elsewhere,

以及其他地方存在生命的可能性

and how we might detect it.

和我們所需的偵測方法

Many ancient religions described

許多古代信仰都敘述

other worlds inhabited by known human beings,

其他存在人類的世界

but these are more like mythical realms

但這些大多是神話

or parallel universes

或平行宇宙

than other planets existing

而不是與地球存在

in the same physical world.

相同物理特性的星球

It is only within the last century

直到最近一世紀

that scientists have been able

科學家才有能力

to seriously undertake the search

嚴謹地從事

for extraterrestrial life.

有關外星生命的研究

We know that at the most basic level

我們知道地球生物

organisms on Earth need three things:

生存所需的三要件為

liquid water,

液態水

a source of energy,

能量來源

and organic, carbon-based material.

和有機、碳基化合物

We also know that the Earth

我們也知道地球和太陽的

is just the right distance from the Sun,

距離恰到好處

so as not to be either frozen or molten.

所以不會太熱或太冷

So, planets within such a habitable range

所以行星和恆星的

from their own stars

距離恰當時

may be able to support life.

可以維持生命

But while we used to think

但過去

that life could only exist

我們僅認為

in such Earth-like environments,

生物只能存在「類地球環境」中

one of the most amazing discoveries of astrobiology

但其中天體生物學最迷人的發現

has been just how versatile life is.

就是生命的多樣性

We now know that life can thrive

我們現在知道

in some of the most extreme environments

生命可以存在許多極端環境中

that'd be fatal for most known organisms.

這些環境讓大多數生物無法生存

Life is found everywhere,

生命無所不在

from black smoke of hydrothermal vents

從黑暗的海底中

in the dark depths of Earth's oceans,

噴發黑煙的深海熱泉

to bubbling, hot, acidic springs

到火山旁邊

on the flanks of volcanoes,

滾燙的酸性溫泉

to high up in the atmosphere.

至大氣層的高處

Organisms that live in these challenging environments

存活在這類極端環境中的生物

are called extremophiles,

被稱為極端微生物

and they can survive at extremes

他們可以存活在極端的

of temperature,

溫度

pressure,

壓力

and radiation,

輻射

as well as salinity,

鹽度

acidity,

酸度

and limited availability of sunlight,

以及僅有有限的陽光

water,

水

or oxygen.

或氧氣的環境中

What is most remarkable about these extremophiles

這些極端微生物最令人驚奇的

is that they are found thriving in environments

是牠們存活的環境

that mimic those on alien worlds.

與外星世界相仿

One of the most important of these worlds

其中一個最重要的星球

is our red and dusty neighbor, Mars.

就是我們紅色、塵土飛揚的鄰居：火星

Today, astrobiologists are exploring places

現在，天體生物學家

where life might once have existed on Mars

利用 NASA 發現號

using NASA's Curiosity rover.

探討火星上 可能曾經存在生命的地方

One of these is Gale Crater,

其中一個地方是蓋爾撞擊坑

an impact crater created

是一個在 38 億年前

when a meteor hit the surface of Mars

由隕石撞擊火星地表

nearly 3.8 billions years ago.

而形成的坑洞

Evidence from orbit suggest past traces of water,

軌道上的證據顯示過去曾有水的痕跡

which means the crater

表示這個坑洞

might once have supported life.

可能曾經存有生命

Planets are not the only places

行星並非唯一

astrobiologists are looking at.

天體生物學家搜尋的地方

For example, Europa, one of the moons of Jupiter,

例如：木星的衛星歐羅巴

and Enceladus and Titan,

兩個土星的衛星

two of Saturn's moons,

土衛二和土衛六

are all exciting possibilities.

都存在可能性

Although these moons are extremely cold

雖然這些衛星很冷

and two are covered in thick ice,

其中兩個被厚實的冰層覆蓋

there is evidence of liquid oceans beneath the shell.

但是證據顯示下方有液態海洋

Could life be floating around in these oceans,

生命是否可能在海洋中浮游

or could it be living around black smoker

或是存在海底

vents at the bottom?

熱泉附近嗎？

Titan is particularly promising

土衛六特別有潛力

as it has an atmosphere

因為它有大氣層

and Earth-like lakes, seas, and rivers

及和地球相仿的湖泊、海洋和河川

flowing across the surface.

覆蓋在地表上

It is very cold, however,

然而它非常寒冷

too cold for liquid water,

冷到會讓水凍結

so these rivers may instead be flowing

所以河流中

with liquid hydrocarbons

可是流動著甲烷或乙烷

such as methane and ethane.

這類液態烴分子

These are composed of hydrogen,

這些由氫

and, more importantly, carbon,

還有，相當重要地，碳組成的分子

which is the basic building block

可以作為已知生命形態的

of all life as we know it.

建構材料

So, could life be found in these lakes?

那麼，我們可能在這些湖中發現生命嗎？

Although instruments are being designed

雖然人類已經開始

to study these distant worlds,

設計偵測遙遠世界的工具

it takes many years to build them

但仍需要數年的時間建造

and even longer to get them

並且以甚至更長的時間

where they need to be.

把它們運到目標地區

In the meantime, astrobiologists work

在此期間，天體生物學家

in our own natural laboratory, the Earth,

用地球這個天然實驗室

to learn about all the weird

學習各種奇特

and wonderful forms of life that can exist

美妙的生命形式

and to help us one day answer

希望有一天能回答

one of humanity's oldest questions:

人類最古老的一個問題：

Are we alone?

我們是獨自一人嗎？