The puzzle of the iron nucleus


Urals scientists from the Institute of Mineralogy and the Institute of Geophysics of the Urals Branch RAS have proposed a new model for the formation of the Earth and the plants of the Earth Group.

The model differs from its predecessors in that it satisfactorily explains the origin of the dense iron nucleus of the planet and the silicate mantle, which, correspondingly, it has a considerable chance of proving to be true.

According to the new model the iron nucleus of the planets in the Earth Group was formed at the early stage of development when the size of the planet was no greater than a few hundred kilometres. Upon compression of the planet cloud it is the minerals that condense first; minerals that contain silicon and aluminium. It is they that comprised the centre of the embryo of the planet. Iron and nickel entered the next layer and they were covered with other rock types. The future planet was still very small, and therefore, many collisions with other bodies could not heat up its surface. It remained hard, although the internal rock was molten, thanks to the energy from the breakdown of short-lived radioactive aluminium isotopes.

At the early stage of the formation of the planets the collision of two small celestial bodies was commonplace. If these bodies have similar sizes, a partially molten alumosilicate nucleus, a fully molten middle shell, made up of iron, and a hard outer shell, their shells will crack and the molten iron layers of both bodies will merge and form the germ of a new body, the nucleus of which already consists of an iron-nickel alloy. It will be covered above by the destroyed pieces of the shell and a planet of the Earth type will begin to grow. According to the calculations of the scientists the adhesion of planet embryos and the formation of an iron nucleus took from 1 to 10 million years. The redistribution of matter within the new planet did not cause any difficulties that were unavoidable with the current sizes of nucleus and mantle, as both planet embryos were very small.

The mechanism for the birth of the Earth, as proposed by the Urals scientists, does not assume the catastrophic collision of fairly large planets. Everything occurs naturally, rapidly and does not contradict contemporary geochemical data.