这里想表达的观点是，当地球从行星胚胎间相互碰撞缓慢形成时，火星却是一个孤独的行星胚胎，在太阳系历史上形成得很早。
The idea here is that - while Earth formed slowly from planetary embryos colliding - Mars is itself a solitary planetary embryo that formed very early in the history of our solar system.
但是天文学家们最终发现如行星这样的大天体间的相互作用方式与地球重力并不相同。
But astronomers eventually saw discrepancies in the way larger objects such as planets interacted.
也许还可能解释这样的事实，那就是在过去大约1亿年间，撞击地球的小行星的数量是原来预计的两倍。
They are probably also the explanation for the fact that, over the past 100m years or so, the number of asteroids that have hit the Earth is about twice that which would have been expected.
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