Friday, 09 Sep, 2011 Science

Meteorites Are Responsible for Bringing Gold to Earth


According to a team of researchers our planet got its precious metals from meteorites.

Scientists from the University of Bristol analyzed some of the oldest rocks on Earth and managed to provide evidence that meteorites are responsible for enriching our planet with gold. The results of the research were published in the journal Nature.

During the formation of Earth, iron sank to the center of our planet and formed its core. The precious metals went together with iron, focusing in the core as well. Thus the mantel remained without gold, platinum, and osmium.

However, the silicate mantle includes up to 1,000 times more gold than it was previously thought and there are several explanations of this fact. One of the reasons is that gold was brought by meteorites but it was previously impossible to offer any evidence.

Recently researchers traveled to Greenland to measure isotopes in rocks that were formed about 4 billion years ago. They were able to estimate the time when the gold was brought to Earth, and to link the delivery to an event that they call the "terminal bombardment".

It is known that our planet formed about 4.55 billion years ago and all of its precious metals concentrated in its core. The terminal bombardment is an event that occurred 3.9 billion years ago when a meteorite hit the Earth and led to the formation of craters that can be observed on the moon. This impact brought gold to our planet and today people can it in the crust.

According to Dr Matthias Willbold, the team's leading researcher, it is rather complicated to estimate the amount of golf since the metal concentrates into nuggets and a large number of rocks has to be studied in order to collect meaningful information. Thus, the team decided to make use of an element called tungsten to prove that gold was brought to the Earth's crust from outer space.

It would be interesting to note that tungsten acts almost like precious metals. However, the element comes in different forms, or isotopes. Scientists examined the amount of different isotopes in modern rocks and made comparison with the results found in ancient rocks. They noticed that old rocks in Greenland did not have tungsten while modern rocks featured this element in significant proportions. This finding allowed researchers to date the input of gold. They say that the date corresponds to the period of terminal bombardment around 3.9 billion years ago.

Back then our planet has been hit with 20 billion billion tons of asteroids. It is for the first time that researchers make such an accurate estimation of tungsten in ancient rocks. So far analysis was made only in Greenland and the team hopes to make more studies in other regions of the planet, reports BBC.

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