Meteors bring gold to the earth

If gold-containing asteroids don't land on Earth about 4 billion years ago, perhaps humans will never see this precious metal.

About 4.2 billion years ago, the earth was just a boiling lava sphere and constantly collided with many other celestial bodies. Those collisions caused gold and platinum - two heavy metal elements - to sink to the center of the globe and form its core. If the available amount of earth does not sink to the core, it can form a layer up to 4m thick on the surface of the globe.

Thus, the amount of gold available on the earth has gone beyond the reach of humans more than 4 billion years ago. So why do we still find gold today right on the outer shell of the earth?

Matthias Willbold, a researcher at the University of Bristol in the UK, thinks that the 'imported' Earth from the universe after its temperature dropped to lava turned into stone , Nature reported.

To prove, Willbold and his two colleagues analyzed many of the ancient stones they took from Greenland. These stones date to 3.8 billion years, but the soil they see is dating back 4.5 billion years. That means that they appear after the core of the earth forms, but before the meteor showers hit the globe.

Thanks to the latest technologies, the team measured the composition of tungsten isotopes - a very rare element - in stones. Like gold, platinum and other precious metals, tungsten also sinks to the center of the earth during the formation of the core.

Isotopes are forms of the same chemical element that have the same number of atoms and protons in the nucleus, but they have different masses because they contain different numbers of neutrons.

After comparing the rock samples in Greenland with the newly formed stones in many other places on the planet, the team found that Greenland rocks have more Tungsten-182 isotopes than the Tungsten-184 isotopes. In contrast, stones in other places contain more tungsten isotopes of 184.

Tungsten-182 was created in the first 50 million years of the solar system's life cycle. Therefore, the research team said that the ancient meteorites brought Tungsten-182 to earth and other precious metals such as gold and platinum. That explains the fact that ancient stones are more tungsten-182 than new ones.

'Our research shows that most of the precious metal on the surface of the earth is brought from space after our planet is bombarded by meteors with a total mass of about 20 billion tons , ' Willbold said.