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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What is even more important is that as the earth cooled down, water began to appear on its surface.

更重要的是当地球冷却后，水就开始出现在它的表面。

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