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.

當提到我們的太陽系時， 你大概想著九大...

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

喔不！是八大行星 繞著太陽沿著軌道運行，

sorry eight, planets orbiting the Sun.

但是在海王星以外， 那遠遠超出太陽熱力範圍的太空，

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

發現到一個鬆散的圓環，

there is a sparse ring found formed by icy chunks

由介於彈珠到小行星般 大小的冰塊所組成。

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

然後在太陽系外緣 再遠上數千倍的距離，

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

有著由小碎塊和氣體所構成的球狀雲，

lies a spherical cloud of small fragments and gases.

這些古老的星塵團 許多是在46億年前

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

太陽系形成時遺留下來的。

of the Solar System 4.6 billion years ago,

有一些在最遠的甚至可能是 來自週邊的星系，

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

但是偶爾來自錯身而過的行星 或星球的引力，

But sometimes the gravity from passing planets or stars

把它們拉向了我們的太陽，

pulls them toward our sun,

展開了一段可以花上 好幾百萬年光陰的旅程。

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

當結了冰的物體移動得更遠進入太陽系

As the frozen object travels further into the Solar System,

太陽就從遠方的小火花 變成一團火海，

the sun grows from a distant spark to an inferno,

在幾十億年前首次把冰溶化了，

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

氣體還有蒸氣把星塵擠到了太空中，

Gas and steam eject dust into space,

形成周圍帶著光的雲團， 被稱為「彗髮」。

forming a bright surrounding cloud, called a coma,

它可以發展到甚至比太陽還大。

that can grow even larger than the sun itself.

同時高能量小粒子巨流 持續被太陽散發出來，

Meanwhile, the intense stream of high-energy particles

就是大家所熟知的「太陽風」，

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

把小粒子吹離彗星的中心

blows particles away from the comet's core,

形成一條達數百萬哩之長 的碎片尾巴，

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

冰、氣體及灰塵反射光線 而閃閃發亮

The ice, gas and dust reflect light glowing brightly.

一顆彗星就誕生了， 在我們太陽系裡與其他剩下的物體

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

一起在繞著太陽的軌道中運行。

in our Solar System.

不過等到彗星飛出了太陽系，

But as the comet travels through the Solar System,

太陽風把分子拆解開又重新 結合成多種的化合物，

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

有少數化合物被科學家發現，

In some of the compounds that scientists found,

首先是北加拿大上空解體之隕石 所留下來的碎塊，

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

還有後來太空船從擦身而過的彗星 尾端所收集到的樣本，

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

就是再簡單不過的氨基酸而已。

were nothing less important than amino acids.

它們根據編碼在DNA裡頭的指引 集合起來成為蛋白質，

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

這些是從細菌到藍鯨等，

these are the main active components in all living cells,

所有的活細胞主要的活性成分。

from bacteria to blue whales.

如果彗星是生命基本要素 最先形成的地方，

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

在後來它們還成了地球上生物 最重要的根源，

then they are the ultimate source of life on Earth,

或許在它們到過的其他地方亦如此。

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

我們幾乎知道夜空中每顆行星的軌道，

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

有五分之一的行星球有近似於地球 的大小和溫度；

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

如果像地球般的行星以及 在DNA裡頭發現的分子不是特例，

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

我們也許就是唯一可能的例子：

we may be only one example of what's possible

當一顆星球在適當的條件下 被擦身而過的彗星

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

埋下了有機分子的種子。

by a passing comet.

所以比起死亡的凶兆好得多了，

So, rather than an omen of death,

彗星最先把氨基酸帶到地球，

the comet that first brought amino acids to Earth

可能還成為了生命前兆。

could have been a portent of life,

有一個遙遠未來的預言，

a prediction of a distant future, where creatures of stardust

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.