Most of the gold on Earth is concentrated in the Earth’s core, beyond the ability of humans to exploit it.

The amount of gold mined by humans is only a small fraction of the amount of gold in the Earth’s core. Photo: Phawatt


Experts calculate that there is so much gold on Earth that it could cover every inch of land to a depth of 50 cm. But gold is still a rare metal because most of it sinks to the Earth’s core and is out of reach of all miners, according to IFL Science.

The Earth’s core consists mainly of iron and nickel. Researchers discovered that through the way geological waves travel from the earthquake through the core. However, the existence of impurities that change the wave density is too difficult to specifically determine, unless their radiation contributes to high temperatures like uranium and thorium.

The existence of impurities containing rare metals remains a mystery. However, in 2006, a group of scientists found a way to estimate their numbers. According to them, some asteroids have a similar composition to Earth because they formed in the same area on the protoplanetary disk. By measuring the carbon chondrite meteorite composition of these asteroids, they were able to calculate the amount of each element present on Earth. Subtracting the known density in the crust and mantle, the team could deduce the amount at Earth’s core of that element.

Professor Bernard Wood, a geologist at Macquarie University, and his colleagues examine the early history of Earth’s development, starting with the formation of the solar system more than 4.5 billion years ago and focusing on into the birth of the Earth’s molten metal core. According to them, the Earth may have been covered by an ocean of molten rock hundreds of kilometers deep during this period. This magma ocean reacted with metals throughout the planet’s development, distilling many important elements, including gold, and depositing them in Earth’s iron-rich core.

After comparing the Earth’s crust with meteorites, the team found that the Earth is chemically very similar to meteorites, but its crust has lost most of the elements mixed with iron such as gold, platinum and nickel. The only place for them to accumulate is in the molten core.

Based on this, Wood and his colleagues were able to calculate the amount of each element mixed with liquid iron and found that more than 99% of Earth’s gold is in the core. Similarly, extant asteroids, especially those representing planetary cores, still retain large amounts of elements. Getting to them is quite difficult, but still much easier than drilling to the core. That’s why NASA plans to launch a probe to the asteroid Psyche in two months.

Articles about the Psyche mission often estimate the value of the asteroid at around $10 billion, but if such a large source of rare metals were available, their value would plummet. The same is true for the price of gold. If humans could bring all the gold from the core to the surface, no one would spend money to buy it anymore.

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