The main theory of the formation of the Earth was called implausible: why it happened

Although the Earth has long been studied in detail, scientists still have to answer some fundamental questions.

One of them concerns the formation of the planet.An international research team led by the Federal Institute of Technology Zurich and the National Competence Center for Planetary Science has come up with an answer to this question. In their study, the scientists used computer modeling and conducted several laboratory experiments. The results of the work were published in the journal Nature Astronomy.

The problem of the old theory

The prevailing theory in astrophysicsand cosmochemistry is that the Earth was formed from chondrite asteroids. These are relatively small, simple blocks of stone and metal that appeared early in the formation of the solar system. The problem with this theory is that no mixture of these chondrites can explain the exact composition of the Earth. It doesn't have as many light, volatile elements like hydrogen and helium as it should.

Over the years, scientists have put forward differenthypotheses that may explain this discrepancy. For example, the collisions of objects that later formed the Earth were thought to release enormous amounts of heat. This eventually evaporated the light elements, leaving the planet in its current composition.

However, the authors of the new study are confident that thesetheories become implausible once the isotopic composition of various elements of the Earth is measured. Thus, all isotopes of a chemical element have the same number of protons, although they have a different number of neutrons. Isotopes with fewer neutrons are lighter and, therefore, should volatilize more easily. If the theory of evaporation during heating were correct, then there would be fewer of these light isotopes on Earth than in the original chondrites. But isotope measurements show a different picture.

New idea

Dynamic models, with the help of whichscientists model the formation of planets and show that the planets in the solar system formed gradually. Over time, small grains turned into kilometer-long planetesimals, accumulating more and more material under the influence of gravitational attraction.

Like chondrites, planetesimals are smallcosmic bodies made of stone and metal. But, unlike chondrites, they were heated enough to differentiate into a metallic core and a rocky mantle. Moreover, planetesimals that formed in different regions around the young Sun or at different times have different chemical compositions.

The question was whether a random combination of different planetesimals could actually form the Earth in the composition known today.

Testing the theory

To find out, the team conducted computer testsmodeling. During this process, thousands of planetesimals collided with each other in the early Solar System. The models were designed in such a way that over time, celestial bodies corresponding to the four rocky planets - Mercury, Venus, Earth and Mars - would emerge from space rocks.

The study found that a mixture of many different planetesimals could actually lead to the composition of the Earth that scientists know about.

How will it help?

Now planetary scientists have a mechanism thatbetter explains the formation of not only the Earth, but also other rocky planets. It could be used, for example, to predict how Mercury's composition differs from that of other rocky planets. Even outside the solar system.