Could comets be the source of life on Earth? - Justin Dowd

彗星有可能是地球上生命的起源嗎? - 賈斯汀‧唐徳

譯者: Harry Chen 審譯者: 瑞文Eleven 林Lim

Humans have observed comets for thousands of years

人類觀察彗星已經好幾千年了，

as their orbits have brought them within visible distance of Earth.

每當彗星循其軌道來到目視距離 地球上的人們就會看到它。

Appearing throughout historical records,

歷史上時有彗星出現的紀錄，

these mysterious lights that came out of nowhere

這些神秘光芒無端地冒出，

and disappeared after a short while

不久之後又消失了，

were thought to be ill omens of war and famine,

當時被看成是戰爭、飢荒的凶兆，

or the wrath of gods.

或者是天神的狂怒。

But recent research has revealed that comets may be even more deeply connected

不過最新的研究發現： 比起這些杜撰的說法所指稱的，

to humanity and our presence on Earth

彗星可能與人類在地球的 出現有更深遠的牽連。

than any of these mythical explanations suggested.

When you think of our Solar System, you probably imagine the nine,

當提到我們的太陽系時， 你大概想著九大...

sorry eight, planets orbiting the Sun.

喔不！是八大行星 繞著太陽沿著軌道運行，

But beyond Neptune, far from the heat of the Sun,

但是在海王星以外， 那遠遠超出太陽熱力範圍的太空，

there is a sparse ring found formed by icy chunks

發現到一個鬆散的圓環，

ranging from the size of marbles to that of small planets.

由介於彈珠到小行星般 大小的冰塊所組成。

And thousands of times farther at the outer reaches of the Solar System

然後在太陽系外緣 再遠上數千倍的距離，

lies a spherical cloud of small fragments and gases.

有著由小碎塊和氣體所構成的球狀雲，

Many of these ancient clumps of stardust are leftovers from the formation

這些古老的星塵團 許多是在46億年前

of the Solar System 4.6 billion years ago,

太陽系形成時遺留下來的。

while some of the most distant may even come from a neighboring system.

有一些在最遠的甚至可能是 來自週邊的星系，

But sometimes the gravity from passing planets or stars

但是偶爾來自錯身而過的行星 或星球的引力，

pulls them toward our sun,

把它們拉向了我們的太陽，

beginning a journey that can take up to millions of years.

展開了一段可以花上 好幾百萬年光陰的旅程。

As the frozen object travels further into the Solar System,

當結了冰的物體移動得更遠進入太陽系

the sun grows from a distant spark to an inferno,

太陽就從遠方的小火花 變成一團火海，

melting the ice for the first time in billions of years.

在幾十億年前首次把冰溶化了，

Gas and steam eject dust into space,

氣體還有蒸氣把星塵擠到了太空中，

forming a bright surrounding cloud, called a coma,

形成周圍帶著光的雲團， 被稱為「彗髮」。

that can grow even larger than the sun itself.

它可以發展到甚至比太陽還大。

Meanwhile, the intense stream of high-energy particles

同時高能量小粒子巨流 持續被太陽散發出來，

constantly emitted by the Sun, known as the solar wind,

就是大家所熟知的「太陽風」，

blows particles away from the comet's core,

把小粒子吹離彗星的中心

forming a trail of debris up to millions of miles long.

形成一條達數百萬哩之長 的碎片尾巴，

The ice, gas and dust reflect light glowing brightly.

冰、氣體及灰塵反射光線 而閃閃發亮

A comet is born, now orbiting the sun along with the rest of the objects

一顆彗星就誕生了， 在我們太陽系裡與其他剩下的物體

in our Solar System.

一起在繞著太陽的軌道中運行。

But as the comet travels through the Solar System,

不過等到彗星飛出了太陽系，

the solar wind tears apart and recombines molecules into various compounds.

太陽風把分子拆解開又重新 結合成多種的化合物，

In some of the compounds that scientists found,

有少數化合物被科學家發現，

first in the rubble left by a meteorite that disintegrated above northern Canada,

首先是北加拿大上空解體之隕石 所留下來的碎塊，

and then in samples collected by a space craft from a passing comet's tail,

還有後來太空船從擦身而過的彗星 尾端所收集到的樣本，

were nothing less important than amino acids.

就是再簡單不過的氨基酸而已。

Coming together to form proteins according to the instructs encoded in DNA,

它們根據編碼在DNA裡頭的指引 集合起來成為蛋白質，

these are the main active components in all living cells,

這些是從細菌到藍鯨等，

from bacteria to blue whales.

所有的活細胞主要的活性成分。

If comets are where these building blocks of life were first formed,

如果彗星是生命基本要素 最先形成的地方，

then they are the ultimate source of life on Earth,

在後來它們還成了地球上生物 最重要的根源，

and, perhaps, some of the other places they visited as well.

或許在它們到過的其他地方亦如此。

We know that planets orbit nearly every star in the night sky,

我們幾乎知道夜空中每顆行星的軌道，

with one in five having a planet similar to Earth in size and temperature.

有五分之一的行星球有近似於地球 的大小和溫度；

If Earth-like planets and the molecules found in DNA are not anomalies,

如果像地球般的行星以及 在DNA裡頭發現的分子不是特例，

we may be only one example of what's possible

我們也許就是唯一可能的例子：

when a planet under the right conditions is seeded with organic molecules

當一顆星球在適當的條件下 被擦身而過的彗星

by a passing comet.

埋下了有機分子的種子。

So, rather than an omen of death,

所以比起死亡的凶兆好得多了，

the comet that first brought amino acids to Earth

彗星最先把氨基酸帶到地球，

could have been a portent of life,

可能還成為了生命前兆。

a prediction of a distant future, where creatures of stardust

有一個遙遠未來的預言，

星塵帶來的生物將會重回太空， 解開他們是從何而來的謎團！

would return to space to find the mysteries of where they came from.