Precious metals are surprisingly abundant in the upper parts of the Earth because a huge meteor shower rained them down out of space, scientists have shown.
The authors of a paper published in Nature analysed different isotopes of tungsten in four billion-year-old rocks taken from Greenland to work out when and how these metals were added to the upper reaches of the Earth.
The findings support the 'terminal bombardment' hypothesis - that the same meteor shower that left the moon scarred with craters also added back rare metals to the upper Earth after the mantle had separated from the core.
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