New model of the emergence of the solar system
Martin Schiller and Martin Bizarro from the University of Copenhagen, and Vera Assis Fernandes from the Natural History Museum in Berlin offered a new model of the emergence of the solar system due to differences in the isotopic composition of the planets. The authors reject the assumption that large and small objects grew simultaneously, but at different rates, and believe that the growth of small bodies ended earlier than large ones.
Almost all specialists today believe that the Sun and the planets were formed from a single protoplanetary cloud. 99.9% of the mass of this disk was on the light. When the Sun broke out, the solar wind blew light hydrogen and helium from the nearest neighborhood of the star, so the gas giants are now beyond the orbit of Mars.
Under the rays of a young star, protoplanetary dust was caked in granules, which are called chondras. Clumping together, these granules formed small stones – chondrites . By the way, this “construction garbage” makes up 90% of meteorites found on the Earth.
Gradually the chondrites were glued together into ever larger bodies – planetesimals. Gravity provided them with an influx of fresh material, and these “embryos” grew until the largest of them became planets, and the rest became asteroids. When the reserves of cosmic dust in the protoplanetary disk were depleted, the growth of the bodies of the solar system was over.
Classical theory suggests that all the bodies of the solar system grew simultaneously, but at different speeds. The more massive the body, the more powerful its gravity and the more surrounding matter it will collect, increasing its size even more as a result. This is the principle of a snowball, or, scientifically, a positive feedback. This law governs the growth of cities (people prefer to travel to megacities, where there is more money and opportunities, why they grow even stronger), the prevalence of languages ??(the more people know the language, the more incentive it is to learn), and so on.
Without questioning the remaining points of the theory, Schiller and his colleagues reject this model of growth. In their opinion, small bodies were unable to grow, as they had the accumulation of material earlier (as experts say, accretion).
As reported in the review of the work of the journal Nature, this idea was inspired by the difference in the isotopic composition of different bodies of the solar system. Namely, the inventors studied the ratio of calcium isotopes 48 Ca and 44 Ca in the world, Mars, Vesta and in samples of rare types of meteorites: ureylitov and angritov ( angrites ).
If all planets and asteroids were formed in a single process from the same cosmic dust, why is the ratio of these isotopes different? Usually this is associated with different distances to the Sun and, accordingly, different temperatures.
However, the authors found that the ratio of calcium isotopes depends on the mass of the celestial body. Masses of the Earth, Mars and Vesta are known from astronomical observations, and the approximate masses of objects, whose fragments are meteorites, scientists have restored based on the properties of “heavenly guests.”
The ratio of isotopes of 48 Ca / 44 Ca is measured by ?48Ca. It is calculated as follows: ? 48Ca = ( 48 Ca / 44 Ca Celestial body – 48 Ca / 44 Ca Earth ) / ( 48 Ca / 44 Ca Earth ). Due to the fact that the differences in the isotope composition are small, ? 48 Ca is measured in parts per million (ppm). By definition, for the Earth ? 48 Ca = 0, and for other bodies this value can be either positive or negative.
Schiller and his colleagues suggested that the inner part of the protoplanetary disk, located inside the current orbit of Jupiter, had low values ??of ? 48 Ca (approximately minus 150 ppm). This material was enough for planetesimals to grow to the size of the body – the homeland of the ureilite (200 kilometers in diameter).
Then the growth of some of these bodies stopped. The same ones that continued to grow increased the mass already at the expense of the outer part of the disk with ? 48 Ca about 200 ppm (a value typical for chondrites formed beyond the orbit of Jupiter). Therefore, the longer the growth lasted, the more the total value of ? 48 Ca turned out to be. Vesta, stopping at a diameter of 530 kilometers, has a minus of 100 ppm, Mars – minus 20 ppm, and the Earth, as already mentioned, 0 ppm.
However, what kind of force made some of these bodies stop growing? This could be a complex gravitational interaction between the “embryos of the planets”, changing their trajectories. Present-day planets with their almost circular orbits lying in the plane of the protoplanetary disk, plied the richest regions of the emerging system and therefore continued to grow. Losers, however, pushed out on elongated, and perhaps, lying in another plane trajectory, remained on a starvation ration.
The conclusion about the different ages of the samples is confirmed by the dating of the content of radioactive isotopes.
However, it can not be said that the new model does not have any problems. For example, to her there are difficult questions in connection with the formation of the moon. “Vesti.Nauka” (nauka.vesti.ru) described in detail about the collision of the Earth with Teia, which gave birth to our companion. It is generally believed that Teiya was significantly smaller than the Earth, but from the theory of the authors it follows that two bodies of the same mass collided. This is not consistent with some known facts.
In addition, there are studies showing that the inflow of matter from the outer part of the protoplanetary disc ceased already in the first millions of years of its existence due to the formation of Proto-Pupiter. It is not easy to explain the composition of chondrites within the framework of the authors’ model.
Probably, in the puzzle under the title “Education of the Solar System” still missing a few important pieces, without which the model that answers all the questions can not be built.
Recall that “Vesti.Nauka” previously wrote about the age of Jupiter and how the substance of the unborn planets merged into the core of the Earth .