(www.neomundo.com.ar/SINC) approximately 0.5% of the Earth’s mantle is derived from the rains of meteorites, as demonstrated by a new study showing high precisely how precious metals, such as gold or silver, in the composition of the layers were added more external of the Earth.
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” The use of isotopic relations in research gives us much more accurate estimates, and is the main breakthrough of our work “, explains Matthias Willbold University of Bristol (United Kingdom) and one of the authors of the article”.
Is 4.5 billion years the Earth in its early stages of training, was an ocean of magma. Molten metals sank and created the core, leaving the mantle devoid of such materials. However, there are still noble metals near the surface. One theory explaining this phenomenon attributes this to a meteor shower 3.9 billion years – i.e., 650 million years ago after the formation of the system solar-, who also created many of the craters moles.
Test this hypothesis has been very difficult due to lack of accuracy on measurements of metals precious.
“We evaluate the tungsten isotope ratios.” It is an element that behaves similar to precious metals; “for example, disappears into the terrestrial core”, explains Willbold.
In addition, the isotopic composition of tungsten on Earth is very different that meteoric material, what allows to use these isotopes to mark the from field of asteroids.
Different ISOTOPES
Willbold team found that the abundance of this isotope in the current surface of the Earth was practically homogeneous. However, detected certain rocks isua greenstone belt (Greenland) cortical above belt with greater presence of the isotope. These formations are very ancient, and show how was the earth before the rain of meteorites (i.e. when the mantle was devoid of noble metals).
“Reflected a decline in the ratio of tungsten, and the current measure only can be explained if about 0.5% of the Earth’s mantle comes from meteoric, material that their design the value after the meteor shower,” says Willbold.
This estimate assumes the mantle of the planet contains 20 trillion tons of matter alien.
These findings support the possibility that meteorites were the source of these metals, including gold, silver, Platinum or rhodium, after the formation of the nucleus.
The authors suggest that even this meteor shower could cause the current dynamics of the mantle.
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