A group of scientists led by ETH Zurich and the National Center of Competence for Research Planets made a new proposal in relation to answering the question: how do formed the earth?
The researchers have published their study in the journal Nature Astronomy.
“The prevailing theory in astrophysics and cosmochemistry is that the Earth formed from chondritic asteroids. These are relatively small, simple blocks of rock and metal that formed early in the solar system,” explains study lead author Paolo Sossi, Professor of Experimental Planetology at ETH Zurich. “The problem with this theory is that no mixture of these chondrites can explain the exact composition of the Earth, which is much poorer in volatile and light elements like hydrogen and helium than we would have expected.”
But Sossi dismisses this theory because he is convinced that these theories become implausible as soon as the isotopic composition of the different elements on Earth is measured.
Therefore, the new hypothesis goes the other way:
‘The dynamical models with which we simulate planet formation show that the planets in our solar system formed progressively. The small grains grew over time into kilometer-sized planetesimals by accumulating more and more material through their gravitational attraction,” explains Sossi. Like chondrites, planetesimals are also small bodies of rock and metal. But unlike chondrites, they have heated up enough to differentiate into a metallic core and mantle rock. “Furthermore, planetesimals that formed in different areas around the young sun or at different times may have very different chemical compositions,” adds Sossi. The question now is whether the random combination of different planetesimals really does result in a composition that matches that of Earth.
To find out, the team ran simulations in which thousands of planetesimals collided with each other in the early solar system. The models were designed in such a way that, over time, they reproduced celestial bodies which correspond to the four rocky planets Mercury, Venus, Earth and Mars. The simulations show that a mixture of many different planetesimals could lead to the effective composition of the Earth.
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