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The Earth's crust contains 1,000 times the amount of gold it should, and it's because ancient meteorites brought it from outer space, according to a new study.
Scientists at the University of Bristol have determined that gold, platinum and other precious metals were delivered long after the Earth formed some 4.5 billion years ago. Such metals that were already part of the planet would have sunk to the core as the Earth cooled, within a few million years. But the abundance of gold in the mantle, embedded in rocks half a billion years younger, indicates the gold was brought by "terminal bombardment," the authors of a study published in the journal Nature say.
This bombardment, a shower of meteorites that also caused the cratering seen on the Moon, would have occurred more than 500 million years after the Earth formed. Scholars say it brought the gold that is now accessible in the Earth's crust.
"The proportions of gold and other precious metals are difficult to measure because they concentrate into nuggets, and we need to analyze a lot of rocks to get meaningful data," lead researcher Matthias Willbold told the BBC.
The period known as terminal bombardment brought 20 billion billion tons of asteroid material down on our planet, Willbold said.