Before it cooled, there was a so-called magma ocean on the Moon's surface - molten rocks, capable of retaining high quantities of water.

在月球冷却之前，它的表面有一个所谓的岩浆海洋-熔融岩，有保持大量水的能力。

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So scientists speculated that our planet's surface water came from comets that slammed into Earth once the planet had cooled.

星球形成模型表明，由于地球早期非常热，所以地球表面不能保持住液态水分子，这使得地球海洋的起源成了谜团。

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The oldest known rocks are about 4 billion years old, yet even they formed roughly half a million millenniums after our planet's surface cooled and water first pooled into shallow seas.

所知道的最古老的岩石出现在大约40亿年之前，而那也仍然是在地球表面冷却和水开始汇聚到浅滩之后大约5亿年才形成。

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