Earth’s gold came from another planet 4.45 billion years ago
It has long been believed that Earth’s precious metals, such as gold and platinum, formed on the planet over the course of several minor impacts.
But new research is challenging this theory, and suggests that a single huge collision with another world could be responsible for the precious metals.
The findings suggest that Earth’s history could have been less violent than previously thought.
Researchers from the Tokyo Institute of Technology led an international team of scientists in the study, in which a computer simulation tracked the evolution of the planets over their first 300 million years.
This is the longest that any team has ever tracked the evolution of the planets.
The results suggest that one large collision formed the precious metals, rather than a series of smaller meteorite impacts over a longer period of time, as was previously thought.
Earth has an unusually high proportion of precious metals near the surface, which is surprising, as they would usually be expected to settle down near the core of the planet.
Until now, this has been explained by the ‘late veneer’ theory, which suggests that foreign objects hit Earth, and in the process deposited the precious metals near the surface.
Speaking to the BBC about the late veneer theory, Matthias Willbold, a geologist at Imperial College London said: ‘ The theory is that after the core formed there was a meteor- ic shower that struck the Earth.
‘ These meteorites contained a certain amount of gold and that replenished the Earth’s mantle and the continental crust with gold.’
But the results from the computer simulation challenge the late veneer theory.
The computer simulation took into account the metal concentrations on Earth, the moon and Mars, and suggests that a huge collision could have brought all the precious metals to Earth at once.
The researchers believe that this happened before the Earth’s crust formed – around 4.45 billion years ago.
Their results also show that there was far less debris and material floating in the inner solar system than scientists had anticipated.
This suggests that the early Earth may have been a more benign place than previously thought.
The researchers hope that their findings will be incorporated into future simulations of the early solar system.