A group of researchers from the University of Klermon-Auverney, together with colleagues from Bayreut University, found evidence that the composition of the Earth had changed because of conflict-related erosion. In a paper published in Science, the group describes a study of the amount of Samaritan and neodymism in meteorites and what it showed them about the processes that had led to the current composition of the Earth.
Previous studies have shown that planets are formed by collisions of material in accretion discs that form around stars in the early years of their existence. It is believed that the characteristics of such collisions play a role in formed planets, for example, in their inclination. Previous studies have also shown that the Earth has a core of iron and nickel, surrounding a layer of iron silicate mixed with magnesium. The upper layer is a layer of silicate. The material density is reduced from core to crust, which researchers point out makes the crust more vulnerable to collisions.
Previous studies have also shown why the bark contains heavier minerals. One theory suggests that they may have been pushed up because of incompatibility with other materials, but these theories do not explain why some minerals are higher in the crust.
Three theories have been developed to explain this anomaly: one is that the core is actually more than the amount that researchers have measured. The other suggests that this is because the material from the accretion disk had different compositions. The third is as the heavier materials were pushed up and stored in the crust, some of them went into space during new collisions.
In the new work, researchers found evidence in favour of a third theory, and they measured the amount of neodym in meteorites, suggesting that their composition was similar to that of earth's building blocks, so they found that up to 20 per cent of the Earth's outer layers might have disappeared from collisions, which explains the ratio of heavy minerals, such as neodes, to cortex compared to other, lighter minerals, such as samaria.