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美国航天局倾力寻找“生命之星”

For decades, looking for life elsewhere in the universe meant listening for signals that could be from distant civilizations. But recent breakthroughs in space technology refocused some of that effort toward finding planets that may harbor life, even in its primitive¹ form.

几十年来，在其它星球找寻生命的迹象无异于苦苦聆听遥远文明传来的信号。但最近，空间科技的最新发展让找到孕育生命的行星成为可能，即使这些生命还处于原始形式。美国之音记者参加了美国航天局在华盛顿总部举行的研讨会上。

When NASA launched the Kepler Space Telescope in 2009, scientists learned something new - and quite significant, says the director of the Space Telescope Science Institute, Matt Mountain.

美国航空航天局（NASA）在2009年发送了“开普勒太空望远镜”。通过它，科学家们有了相当重大的发现。

“Our galaxy² has at least 100 billion planets in it. And we didn't know that five years ago," said Mountain.

太空望远镜科学研究所主任马特?蒙特恩说：“银河系至少有一千亿颗行星。五年前我们都不知道这一点。”

Of course, Kepler and today's other powerful telescopes cannot actually see those planets; they are too faint against the light of their stars.

当然，开普勒以及其它功能强大的望远镜都无法真的看到那些行星。相对于它们环绕的恒星而已，这些行星的光芒太微弱了。

But scientists can measure the change of light when they pass in front of the star and analyze³ the light passing through their atmosphere to determine what is in it.

但是，当这些行星在运转到恒星前时，科学家们可以测量到光的变化，并通过分析穿越大气的光，确定行星上的物质。

“Well, if we were looking at Earth, we would see signs of our sky, our blue sky, we would see signs of oxygen, of carbon-dioxide, of sulfur⁴ dioxide from volcanoes and we might even see signatures that there was plant life," said NASA's astrophysicist and former astronaut John Grunsfeld. "And we see that by dissecting⁵ the light into its component⁶ colors."

美国航天局的天体物理学家、前宇航员约翰?格伦斯菲尔德说：“如果我们看地球，我们能看到地球上的蓝色天空，我们能看到有氧气、二氧化碳和火山中喷发出的二氧化硫的迹象，甚至能看到存在植物的特征。我们能够通过解剖组成光的种种颜色看到这些。”

Most of the planets discovered so far are unlike Earth. They are too big, too small, too close to their sun, or too far away to support life. But astrophysicist Sara Seager says small planets the size of Earth are extremely common.

目前发现的大多数行星都与地球不一样。它们不是太大、就是太小；不是太接近恒星，就是离恒星太远，无法孕育生命。但是天体物理学家萨拉?西格表示，银河系中像地球这么大的小行星到处都是。

“We're looking for biological signatures, gasses that are produced by life, gasses that don't belong in the atmosphere," said Seager.

她说：“我们在寻找生物体的特征，是由生命产生的气体，而不是属于大气层的气体。”

In cooperation with the European Space Agency and scientists from other nations, NASA is building the next generation of space telescopes that may be able to find evidence of life.

通过与欧洲航天局以及其他国家科学家的合作，美国航天局正在建造能探索生命迹象的新一代太空望远镜。

The James Webb Space Telescope, scheduled to be deployed⁷ in 2018, will have unprecedented⁸ sensitivity and resolution that will greatly improve the spectroscopic analysis of distant stars and planets.

计划于2018年升空的詹姆斯?韦伯太空望远镜将拥有前所未有的敏锐度和清晰度，可改善科学家们对遥远的恒星和行星的光谱分析能力。

NASA’s chief scientist Ellen Stofan says the agency also plans to look for life on Jupiter’s moon Europa, which may have an ocean under its ice cover.

美国航天局首席科学家艾伦?斯托凡表示，他们还计划在木星的卫星“欧罗巴”（木卫二）上寻找生命迹象。它的冰层下可能有海洋。

“In our own solar system we know where to go, we know what to measure it and we're in the process of doing just that. Looking out, beyond our solar system, we're on the right track, we're making the right measurements and we're just on the cusp of learning so much," said Stofan.

他说：“我们熟悉我们自己的太阳系，知道如何测量它，我们正在这么做。此外，在太阳系之外，我们也步入正轨，我们在进行正确的测量，我们学到了很多，就处在突破点上。”

Scientists say there's a very high probability that they will find a planet very much like Earth. That could help answer the question: how hard is it for life to get a foothold in the universe?

科学家们表示，他们有很大机会找到酷似地球的行星。他们将揭谜：在浩瀚的宇宙中，生命的存在到底有多难？