Gold came from space
When the Earth formed, molten iron sank down to form its core, taking
the vast majority of the planet’s precious metals with it.
Indeed, the quantities of metals such as gold and platinum present in the core would be sufficient to cover the entirety of the Earth’s surface in a four-metre-thick layer. So where did the metals present in the crust come from?
The current theory is that a cataclysmic meteorite shower was responsible, and it was this theory that was tested by researchers at the University of Bristol. Matthias Willbold and Tim Elliott analysed rocks from Greenland that came from the window between the early formation of the Earth and the proposed meteorite bombardment – almost four billion years ago.
They used ultra-high-precision analyses to compare the ratios of tungsten isotopes in the rocks with those found in modern-day rocks. The results indicated a 15 parts per million decrease in the relative abundance of one particular isotope, which strongly agreed with theoretical levels required to explain the excess of accessible gold on Earth as the by-product of meteorite bombardment.
‘Our work shows that most of the precious metals on which our economies and many key industrial processes are based have been added to our planet by lucky coincidence when the Earth was hit by about 20 billion billion tonnes of asteroidal material,’ Willbold said.
October 2011
Indeed, the quantities of metals such as gold and platinum present in the core would be sufficient to cover the entirety of the Earth’s surface in a four-metre-thick layer. So where did the metals present in the crust come from?
The current theory is that a cataclysmic meteorite shower was responsible, and it was this theory that was tested by researchers at the University of Bristol. Matthias Willbold and Tim Elliott analysed rocks from Greenland that came from the window between the early formation of the Earth and the proposed meteorite bombardment – almost four billion years ago.
They used ultra-high-precision analyses to compare the ratios of tungsten isotopes in the rocks with those found in modern-day rocks. The results indicated a 15 parts per million decrease in the relative abundance of one particular isotope, which strongly agreed with theoretical levels required to explain the excess of accessible gold on Earth as the by-product of meteorite bombardment.
‘Our work shows that most of the precious metals on which our economies and many key industrial processes are based have been added to our planet by lucky coincidence when the Earth was hit by about 20 billion billion tonnes of asteroidal material,’ Willbold said.
October 2011
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