September 8, 2011
Meteorites May Have Brought Precious Metals To Earth
Precious metals such as gold, platinum and tungsten were brought to Earth by a massive meteorite shower that occurred approximately 650 million years after the planet formed, scientists from the University of Bristol revealed on Wednesday.
According to a university press release, researchers Dr. Matthias Willbold and Professor Tim Elliott of the university's School of Earth Sciences, studied nearly four billion year old rock samples recovered from Greenland.
The samples, which had originally been collected by Oxford University professor Stephen Moorbath, "provide a unique window into the composition of our planet shortly after the formation of the core but before the proposed meteorite bombardment," the school's media advisory added.
According to Ted Thornhill of the Daily Mail, the Bristol University team "also discovered there is enough gold and platinum in the Earth's core to plate the surface of the globe with a layer of priceless bling four meters thick. These huge gold deposits appeared during the Earth's formation when molten iron sank to its centre, dragging with it vast quantities of precious metals."
In their research, published in the September 8 edition of the journal Nature, the scientists determined the tungsten isotopic composition of the rocks in question. Like gold and similar precious metals, tungsten is made up of several isotopes and should have entered the planet's core when it first formed.
However, Dr. Willbold reported noticing a 15 parts-per-million decrease in relative abundance of one such isotope (182W) between the Greenland sample and modern-day rocks. In their press release, the university calls it a "small but significant change" that is in "excellent agreement with that required to explain the excess of accessible gold on Earth as the fortunate by-product of meteorite bombardment."
He told Rachel Kaufman of National Geographic News, "These rocks that we found on Greenland are the only ones that show an anomalous tungsten condition," which she referred to as "a sign that meteor impacts did in fact change Earth's surface composition."
"Extracting tungsten from the rock samples and analyzing its isotopic composition to the precision required was extremely demanding given the small amount of tungsten available in rocks. In fact, we are the first laboratory world-wide that has successfully made such high-quality measurements," Willbold also noted in a statement.
He added, "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 approximately 20 billion billion metric tons worth of material originating from asteroids.
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