It has long been thought that the seeds for life came to a primordial Earth from solar system leftovers crashing into the planet.

人们一度设想，正是来自太阳系中的宇宙残骸，为原始地球带来了生命之种。

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If explore for the earth with long time scale, the earth changes may emerge from solar system, and the earth catastrophisms may emerge from Galactic System.

从长时间尺度看，在地球绕太阳运动过程中会涌现出全球变化特性；

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Second, Jupiter's enormous mass prevents most Sun-bound comets from penetrating the inner solar system.

其次，木星的巨大质量阻止了大多数与太阳结合的彗星穿透太阳系内部。

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But last month,a computer programmer from Australia made an exciting discovery of an unusual event in Earth's solar system.

VOA: special.2009.08.25

An object in the solar system could be identified if it appeared to move from its place in the earlier photograph.

VOA: special.2010.07.11

Some scientists have called Jupiter the protector of the inner planets and our own Earth -- from objects from the outer solar system.

VOA: special.2009.08.25

Now, researchers speculate that it is the first known meteorite from our Solar System's innermost planet, Mercury.

BBC: Mercury meteorite puzzle

Either that or, if the tweaking is in the wrong direction, it gets ejected from the solar system altogether.

ECONOMIST: Comet Ikeya-Zhang is enlivening the skies

In that case, he calculates, the chance of life having crossed to the earth from another solar system, or vice versa, is about 1%.

ECONOMIST: Panspermia: Interplanetary migration | The