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there is an issue of how much this composition depends on the fact that life has been present for billions of years
It is assumed that initially the Earth started out with vast amounts of iron dissolved in the world's acidic seas. Eventually, as photosynthetic organisms generated oxygen, the available iron in the Earth's oceans was precipitated out as iron oxides.
As this happened about 2 billion years ago, clearly primitive life evolved in a very different environment from the current one.

Those whom the Gods wish to destroy They first make mad. -- Euripides
by Migeru (migeru at eurotrib dot com) on Sun Oct 8th, 2006 at 11:13:09 AM EST
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