在很大程度上，Roids 只是小行星和彗星的小碎片。

Roids are, for the most part anyway, they are just smaller bits of asteroids and comets.

youdao

这颗彗星的轨道和地球的轨道相交。

The orbit of this comet intersects the orbit of the Earth.

《柯林斯英汉双解大词典》

它们与来自彗星的尘埃颗粒结合在一起，形成了巨大的云团。

They combine with dust particles from the comet to form a huge cloud.

youdao

Suppose the planet were hit by a comet-- this happened--something like this happened sixty-five million years ago, so it could happen again.

假设这个星球被一颗彗星击中-,这样的事，大约六千五百万年前,发生过，所以它还可能再发生。

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