每日一翻：Young Earth May Have Been All Wet

Water. Earth has loads of H₂O. But did it always? This question has plagued scientists for decades. Conventional wisdom has it that the Earth formed without any water. Then meteorites carrying water smashed into the planet, dumping their precious cargo. But now, a team of geologists has challenged this idea. They say water may have been here from the start.

地球上有大量的水，但是会一直这样吗？这个问题已经困扰科学家们几十年了。传统科学认为地球形成的时候没有任何水，随后存在水的陨石撞向地球，把大量的水倾卸到地球上。但是现在，一个地理学家小组对这一观点提出质疑。他们说地球在形成的时候就已经存在水了。

The scientists discovered that the chemical signature of water on Earth matches the signature of water in an ancient group of asteroids called eucrites. These bodies formed just a few million years after the birth of the solar system. And because Earth and eucrites seem to share the same source of water, the reasoning goes, Earth must have gotten its water around the same time the eucrites did—which has big implications.

科学家们发现地球上的水的化学特征与一个被称为钙长辉长无粒陨石的古老的小行星群上的水的化学特征相匹配。这些星体在太阳系诞生100万年之后形成。因为地球和钙长辉长无粒陨石的水有相同的来源，由此推断，地球和钙长辉长无粒陨石一定是在同一时期出现了水。这个推断产生了巨大的影响。

“Because Earth got its water early—really the whole inner solar system got its water early—it means that planets, once they fully formed and got cool enough that water would be stable on the surface, they could be habitable.”

“因为地球上出现水比较早，事实上整个太阳系内部出现水都很早，这意味着行星完全形成后，如果温度足够低，水就会在表面稳定，行星就变得可居住了。”

The Woods Hole Oceanographic Institution’s Adam Sarafian, who led the research. [Adam Sarafian et al, Early accretion of water in the inner solar system from a carbonaceous chondrite–like source, in Science]

伍兹霍尔海洋研究所的亚当•萨拉芬带领了这次研究。

“It wasn’t like these planets are just waiting around, looking at their watches, saying, ‘Where’s the water? Life’s ready to go, we just need water here.’ So it pushes the date at which planets can become habitable back. And we need to go back to the drawing board on how planets are built and how water survives large impacts.”

“这并不像那些行星只是看着时间等待，说‘水在哪？生命准备好了，我们正好需要水。’所以地球可以成为宜居行星的日期被向后推了。我们需要从头开始，重新去研究行星如何形成以及水的重大影响。”

—Julia Rosen