An international research team proposes a new theory to explain the Earth’s formation process.
In this way, an answer could be given to an unknown that, despite being the subject of several studies for a long time, still does not generate consensus in the scientific community, also providing an explanation of how other rocky planets were formed.
New efforts to decipher the origin of our planet
Over the years, several hypotheses have been proposed to explain the origin of planet Earth, without overcoming the discrepancies that the various theories that have emerged raise in the scientific community. For example, it was postulated that the collisions of the objects that later formed the Earth generated huge amounts of heat that vaporized the light elements, leaving the planet in its present composition.
An international research team led by the Federal Technical School (ETH) in Zurich and the Swiss National Center for Research Competence, PlanetSrecently proposed a new answer to the question behind Earth’s origin, based on laboratory experiments and computer simulations.
“The prevailing theory in astrophysics and cosmochemistry is that the Earth formed from chondritic asteroids. These are simple, relatively small blocks of rock and metal that formed early in the solar system.” Explain the study’s 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 Earth, which is much poorer in light and volatile elements like hydrogen and helium than we had expected.“, he added.
For Sossi, many of these theories, like the one mentioned above, become implausible once the isotopic composition of Earth’s different elements is measured. “All isotopes of a chemical element have the same number of protons but different numbers of neutrons. Isotopes with fewer neutrons are lighter and therefore should be able to escape more easily. If the heating vaporization theory were correct, we would find fewer of these light isotopes on Earth today than in the original chondrites. But that’s exactly what isotope measurements don’t show.”observed the researcher.
Sossi’s team opted to find another solution. “The dynamic models with which we simulated the formation of planets show that the planets in our solar system formed progressively. The tiny grains became kilometer-sized planetesimals over time as they accumulated more and more material through their gravitational pull.”He explained.
One of the aspects in which some debated theories coincide is the possibility that the planet originated from the collision of other “small planets”. Like chondrites, planetesimals are also small bodies of rock and metal. But unlike these chondrites, they were heated 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 can have very different chemical compositions.”Sossi adds. This raises the question of whether the random combination of different planetesimals actually results in a composition that matches that of Earth.
To find out, the team ran simulations in which thousands of planetesimals collided with each other within an early solar system. The models were designed in such a way that, over time, the celestial bodies corresponding to the four rocky planets Mercury, Venus, Earth and Mars were reproduced. The simulations developed showed that a mixture of several different planetesimals could lead to the effective composition of the Earth. Furthermore, the composition of the Earth is even the most statistically likely result of all the simulations performed.
“Although we were suspicious, we found this result very remarkable”Sossi remembers. “Now we not only have a mechanism that better explains the formation of Earth, but we also have a reference to explain the formation of the other rocky planets”indicated the researcher.
The mechanism used in this study could be used, for example, to predict how Mercury’s composition differs from that of other rocky planets. Likewise, it could be used to determine how rocky exoplanets from other stars might be composed.
“Our study shows how important it is to consider dynamics and chemistry when trying to understand planetary formation.”commented Sossi. “I hope that our findings will lead to closer collaboration between researchers in these two fields.”he added.
The results of this research were published in an article in Nature astronomy.