(ORDO NEWS) — Oddly enough, in fact, we still do not know exactly how our planet was formed. The researchers have the general idea, but the finer details are much harder to unravel.
Scientists have developed a model that is currently considered the most likely explanation for this process: the Earth formed as a result of the gradual accretion of asteroids. However, even within the framework of this theory, there are some facts that are difficult to explain.
A new paper that combines experimentation with simulations has revealed a new formation path that matches Earth’s characteristics much better.
Born from asteroids?
Chondrite asteroids are relatively small, simple blocks of rock and metal that formed early in the solar system.
The problem with the “asteroid” theory is that no mixture of these chondrites can explain the exact composition of the Earth, which is much poorer in light volatile elements like hydrogen and helium than it should be, according to planetary scientist Paolo Sossi of ETH Zurich.
The process of planet formation raises a lot of questions, but scientists managed to get the big picture. When a star forms from a dense clump of matter in a molecular cloud of dust and gas in space, the matter around it takes the form of a disk that rotates around the growing sun.
The small densities within this whirlpool of matter also coalesce into smaller and colder clumps. Small particles collide and stick together, first electrostatically and then gravitationally, forming larger and larger objects that can eventually grow into a planet. This is the so-called. accretion model, which is fully confirmed by observational data.
But if the rocks stuck together are chondrites, the missing lighter volatiles are an open question.
Scientists have presented various explanations, including the heat generated during the collisions, which may have evaporated some of the lighter elements.
This, however, is not always true: according to recent experimental work by Saussy, heat would evaporate the lighter isotopes of elements with fewer neutrons. But lighter isotopes are still present on Earth in about the same proportions as in chondrites.
So Saussy and his colleagues decided to explore another possibility: the rocks that formed the Earth were not chondrite asteroids from the Earth’s general orbital neighborhood, but planetesimals.
These are larger bodies, the “seeds” of the planets, which have grown to a size sufficient to have a differentiated core.
“The dynamical models with which we simulate the formation of planets show that the planets in our solar system formed gradually.
Small grains eventually turned into kilometer-sized planetesimals, accumulating more and more material due to gravitational attraction, ”saussi explained.
Planetesimals that formed in different regions around the young Sun or at different times can have very different chemical compositions, he says.
The model was developed for the inner solar system that we see today: Mercury, Venus, Earth and Mars. The team found that a diverse mixture of planetesimals with different chemical compositions could replicate the Earth as we see it today.
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