火星上是否存在远古海洋的想法已经争论了20年。

The idea of a large ancient ocean on Mars has been debated for two decades.

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在大规模灭绝之前，高等海洋肉食生物是远古的鲨鱼。

Before the mass extinction, the top ocean predators were primitive sharks.

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在大规模灭绝之前，高等海洋肉食生物是远古的鲨鱼。

Before the mass extinction, the top ocean predators were primitive sharks.

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