More than 20% of the Earth was eroded by cosmic influences during its formation!

How was the earth formed? This is a question that is still under discussion. Because there is a certain chemical anomaly in the composition of the Earth’s crust which indicates that our planet was not formed simply by accretion of minor planets.

whether The number of discovered exoplanets continues to increase, examples with characteristics close to those on Earth remain very rare. Is this apparent rarity related to the difficulties in discovering these small, rocky planets? Or does the Earth have certain characteristics in the way it was formed?

True, the processes leading to the formation of planets are still not well understood. Several recent studies also point to the fact that the current composition of the Earth does not quite match what would be expected if the planet had formed only through the accumulation of primitive rocky meteorites (chondrites).

Birth in the chaos of collisions between minor planets

So far, the preferred model to explain the formation of rocky planets has actually mainly involved collisions. It began with the collapse of the solar disk made of dust and gas. Besides the Sun, many minor planets, called minor planets, were formed by the accumulation of this material. by collision, These many small planets gave rise to larger and larger bodiesuntil the various rocky planets that characterize the inner part of the solar system.

This forming process requires a huge number of collisions. A mechanism favored by the increasing gravitational pull of protoplanets, in connection with their growth. This is the time of giant collisions, like the ones that led to moon formation. This period of intense bombardment by minor planets was crucial in shaping the Solar System as we know it today.

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But what is the effect of these collisions on the chemical composition of rocky planets? For Paul Frossard of the Magmas and Volcanology Laboratory in Clermont-Ferrand and colleagues, the chemical composition of the primordial Earth’s crust would have changed over time in response to the erosion caused by these multiple cosmic effects.

Abnormalities in chemical composition due to corrosion from cosmic influences

Since 2005, we’ve known that there is a huge discrepancy between the composition of the Earth’s crust and that of the chondrites, these rocky meteorites that contributed to the formation of the Earth. In particular, the Earth appears to be enriched at 142Nd (neodinium) compared to 144Nd. Neodynium is a heavy element, but it is incompatible with mantle formation, which thus tends to be ‘knocked out’ towards the surface and end up forming the crust. Several hypotheses have been proposed to explain this anomaly. The first indicates that our observations are biased by the fact that we can only analyze the surface layers of the Earth and that the formation of more inner levels will return to the expected formation of chondrites. Another hypothesis suggests that the formation of the solar disk was not uniform and that it was the minor planets themselves that were exhausted in 142 AD.

But Paul Frossard nonetheless suggests another solution. primitive crust of the earth It can be constantly eroded by meteorite impacts during its formation, resulting in the loss of elements preferentially present in the crust, such as 144Nd. 142Nd is caused by the radioactive decay of 146Sm (samarium), an element found in the crust but also in the mantle, this erosion process explains the final increase of 142 nm compared to 144Nd.

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20% of the ground is torn during impacts

According to the results published in the journal Science, more than 20% of the Earth was “dissected” by collisions during its formation. This hypothesis will also make it possible to explain other “abnormalities” in the composition, in particular the depletion of some rare earth elements such as uranium, potassium and thorium.

Is this planetary erosion mechanism typical during the formation of rocky planets? Or is it an earthly privacy? The new research could make it possible to determine to what extent this pattern of formation could affect Earth’s ability to support life.

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