The majority of gold on Earth is concentrated in the Earth’s core, beyond the reach of human extraction.
Experts estimate that there is so much gold on Earth that it could cover every inch of land to a depth of 50 cm. However, gold remains a rare and precious metal because most of it is submerged in the Earth’s core and is out of reach for any miner, according to IFL Science.
The amount of gold extracted by humans is only a small fraction compared to the gold in the Earth’s core. (Photo: Phawatt)
The Earth’s core is primarily composed of iron and nickel. Researchers discovered this through the way seismic waves travel from earthquakes through the core. However, the existence of a mass of impurities that affects wave density is difficult to pinpoint specifically, unless their radiation contributes to high temperatures like uranium and thorium.
The existence of impurities containing rare precious metals remains a mystery. However, in 2006, a group of scientists found a way to estimate their quantity. They theorized that some asteroids have a composition similar to Earth because they formed in the same region of the protoplanetary disk. By measuring the composition of carbon chondrite meteorites from these asteroids, they could calculate the amount of each element present on Earth. By subtracting the known densities in the crust and mantle, the research team could infer the quantity of that element in the Earth’s core.
Professor Bernard Wood, a geologist at Macquarie University, and his colleagues examined the early developmental history of Earth, starting with the formation of the solar system over 4.5 billion years ago and focusing on the formation of Earth’s molten metallic core. According to them, Earth may have been covered by an ocean of molten rock several hundred kilometers deep at that time. This magma ocean reacted with metals throughout the planet’s development, refining many essential elements, including gold, and depositing them in the iron-rich core of the Earth.
After comparing the Earth’s crust with meteorites, the research team found that Earth is chemically very similar to meteorites, but its crust has lost most of the elements dissolved in 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 calculated the amount of each element mixed with liquid iron and discovered that over 99% of the gold on Earth lies in the core. Similarly, existing asteroids, especially those representing the cores of planetary embryos, still retain large amounts of these elements. Accessing them is quite challenging, but it is still much easier than drilling to the core. That is 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 to be around $10,000 trillion, but if such a large source of rare precious metals were available, their value would plummet. The same is true for gold. If humans could bring all the gold from the core to the surface, no one would buy it anymore.
