The first embryos of planets and asteroids appeared unexpectedly early - about a million years after the birth of the Sun, which indicates the very rapid formation of the Earth and other planets of the solar system, according to an article published in the journal Science Advances.
“The discovery of thousands of exoplanets outside the solar system showed that the birth of the Earth was not unique, but quite an ordinary event for the Galaxy. We used to think that the planets formed gradually, increasing in size from dust particles to 100-kilometer planetary embryos, but recent observations of this process in other star systems show that their formation was almost instantaneous,”writes Jean Bollard of the University of Copenhagen (Denmark) and his colleagues.
According to scientists, the solar system began to form about 4.6 billion years ago as a result of the gravitational collapse of a giant interstellar molecular cloud. Most of the matter went to the formation of a star - the Sun, and a rotating protoplanetary disk was formed from its remnants, from which planets, their satellites, asteroids and other small bodies of the solar system later arose.
Traces of this primary matter are the so-called chondrites - rather porous asteroids and meteorites, consisting of primitive rocks and almost free of metals. The main distinguishing feature of these "building blocks" of the planets are the so-called chondrules - microscopic balls of remelted rocks that arose in the first moments of the life of the solar system.
Bollard and his colleagues, studying the chemical and isotopic composition of several ancient meteorites found in Morocco at the end of the last century, found out when these chondrules appeared and how they influenced the birth of the "building blocks" of the Earth and other planets of the solar system.
Scientists were able to calculate the age of the meteorites using an unusual pattern found in the matter of the newborn solar system. According to planetary scientists, it contained strictly defined amounts of two isotopes of uranium - long-lived uranium-238 with a half-life of four billion years and short-lived uranium-235 with a half-life of 0.7 billion years.
The end products of the decay of both radionuclides are two different lead isotopes - lead-207 for uranium-235 and lead-206 for uranium-238. Therefore, scientists can very accurately calculate the age of any rock by measuring the proportion of these isotopes, if it has not been melted during its existence. This condition is automatically fulfilled for chondrules, since they were formed at the time of the birth of the solar system and did not change anymore.
Guided by this idea, planetary scientists extracted 17 chondrules from meteorites and calculated their age, which turned out to be the same for almost all meteorites - approximately 4564-4567 million years. This means that chondrules formed over a very short period of time, in the first million years of the life of the solar system after the birth of the sun.
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Such a rapid formation of the future “building blocks” of the Earth and other planets indicates that the process of the birth of planets was much faster than the classical theories of the birth of the solar system indicate. Scientists believe that chondrules themselves accelerated the formation of large asteroids and protoplanetary bodies, being both a catalyst and a starting material.
