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Humans have observed comets for thousands of years as their orbits have brought them within visible distance of Earth.
人类观察彗星已经有上千年的历史了，这是因为它们的轨道让它们出现在地球的可视距离以内。
Appearing throughout historical records,
在所有的历史记录中，
these mysterious lights that came out of nowhere and disappeared after a short while
这些神秘的光不知道从何处来，而且一瞬即逝，
were thought to be ill omens of war and famine, or the wrath of gods.
它们曾被认为是战争和饥荒的征兆，或者是神的愤怒。
But recent research has revealed that comets may be even more deeply connected to humanity and our presence on Earth
但是最新的研究揭示了彗星更可能和地球上人类的出现有着深远的联系，
than any of these mythical explanations suggested.
这远超出于那些神秘的解释。
When you think of our Solar System, you probably imagine the nine, sorry eight, planets orbiting the Sun.
当你想到太阳系，大概会想到9个，哦不，是8个行星围绕着太阳。
But beyond Neptune, far from the heat of the Sun,
但是在距离太阳的光热最远的海王星之外，
there is a sparse ring found formed by icy chunks ranging from the size of marbles to that of small planets.
还有一个由稀疏的冰块组成的环形带，它们的尺寸从大理石块到小型的行星不等。
And thousands of times farther at the outer reaches of the Solar System lies a spherical cloud of small fragments and gases.
在与之距离几千倍远的太阳系外围有着碎片和气体形成的天体云。
Many of these ancient clumps of stardust are leftovers from the formation of the Solar System 4.6 billion years ago,
许多这些古老而成簇的星团都是源于46亿年前太阳系的形成，
while some of the most distant may even come from a neighboring system.
同时还有最遥远的，可能甚至来自于相邻的星系。
But sometimes the gravity from passing planets or stars pulls them toward our sun,
但是有时经过的行星或恒星的引力会把他们拉向我们的太阳，
beginning a journey that can take up to millions of years.
这个过程可以需要有几百万年。
As the frozen object travels further into the Solar System,
当冻结的物体行至太阳系，
the sun grows from a distant spark to an inferno, melting the ice for the first time in billions of years.
太阳向远处发出的火焰，会第一次融化这些冷冻了几十亿年的冰。
Gas and steam eject dust into space, forming a bright surrounding cloud, called a coma,
气体和蒸汽带着尘埃排向太空，形成了明亮的云，这样的云就是“彗形像差”，
that can grow even larger than the sun itself.
它的大小甚至可以超过太阳本身。
Meanwhile, the intense stream of high-energy particles constantly emitted by the Sun, known as the solar wind,
同时，一股高能量粒子不断地从太阳释放出来--太阳风，
blows particles away from the comet's core, forming a trail of debris up to millions of miles long.
把粒子不断的吹离彗星核，由碎片组成了一条上百万英里长的踪迹。
The ice, gas and dust reflect light glowing brightly.
冰、气体和尘埃反射了明亮的光。
A comet is born, now orbiting the sun along with the rest of the objects in our Solar System.
一颗彗星这样诞生了，围绕着太阳和其他在我们的太阳系中的物体。
But as the comet travels through the Solar System,
但是，就在彗星穿越太阳系的时候，
the solar wind tears apart and recombines molecules into various compounds.
太阳风会把分子分解并重新组合为不同的化合物。
In some of the compounds that scientists found,
在一些科学家已经发现的化合物中，
first in the rubble left by a meteorite that disintegrated above northern Canada,
第一次在加拿大北部上空分解的陨石碎片中发现了这样的物质，
and then in samples collected by a space craft from a passing comet's tail, were nothing less important than amino acids.
之后在从经过彗星尾的航天器上也发现的东西，只不过是一些氨基酸。
Coming together to form proteins according to the instructs encoded in DNA,
它根据DNA代码组成了蛋白质，
these are the main active components in all living cells, from bacteria to blue whales.
这些都是主要的活性细胞的组成部分，从细菌到蓝鲸。
If comets are where these building blocks of life were first formed,
如果彗星是这些生命迹象产生的地方，
then they are the ultimate source of life on Earth,
那它们就是地球生命的根本源头，
and, perhaps, some of the other places they visited as well.
并且也许是它们经过别的地方的生命源头。
We know that planets orbit nearly every star in the night sky,
我们知道夜空中的行星会绕着每一个恒星的轨道运行，
with one in five having a planet similar to Earth in size and temperature.
五分之一的行星有着和地球相似的大小和温度。
If Earth-like planets and the molecules found in DNA are not anomalies,
如果类似地球的行星和DNA分子并不是特例的话，
we may be only one example of what's possible when a planet under the right conditions is seeded with organic molecules by a passing comet.
我们的存在则给出了唯一的例证：当彗星经过一个处在能够孕育有机分子的适当条件的行星时可能会发生的结果。
So, rather than an omen of death, the comet that first brought amino acids to Earth could have been a portent of life,
所以，如果说是死亡的预兆，不如说彗星带来了地球上第一个氨基酸，也带来了生命的迹象，
a prediction of a distant future, where creatures of stardust would return to space to find the mysteries of where they came from.
带来了遥远未来的预兆，这些从星尘上来的生物会回到太空寻找它们的起源。
