American geologists say that the inner core of the Earth could not have arisen 4.2 billion years of the Earth in the form in which scientists imagine it today, since this is impossible from the point of view of physics, according to an article published in the journal EPS Letters.
“If the core of the young Earth consisted entirely of a pure, homogeneous liquid, then the inner nucleolus should not exist in principle, since this matter could not cool down to the temperatures at which its formation was possible. Accordingly, in this case, the core may be heterogeneous in composition, and the question arises as to how it became so. This is the paradox we have discovered,”says James Van Orman of Case Western Reserve University in Cleveland (USA).
In the distant past, the Earth's core was completely liquid, and did not consist of two or three, as some geologists today suggest, layers - the inner metal core and the surrounding melt of iron and lighter elements.
In this state, the core quickly cooled and lost energy, which led to a weakening of the magnetic field generated by it. After some time, this process reached a certain critical point, and the central part of the nucleus "froze", turning into a solid metallic nucleolus, which was accompanied by a burst and growth in the strength of the magnetic field.
The time of this transition is extremely important for geologists, as it allows us to roughly estimate how fast the Earth's core is cooling down today and how long the magnetic shield of our planet will last, protecting us from the action of cosmic rays, and the Earth's atmosphere from the solar wind.
Now, as Van Orman notes, most scientists believe that this happened in the first moments of Earth's life thanks to a phenomenon that can be analogous to the planet's atmosphere or in soda machines in fast food restaurants.
Physicists have long discovered that some liquids, including water, remain liquid at temperatures noticeably below the freezing point if there are no impurities, microscopic ice crystals or powerful vibrations inside. If it is easy to shake it up or dip a speck of dust into it, then such a liquid will freeze almost instantly.
Something similar, according to geologists, happened about 4.2 billion years ago inside the Earth's core, when part of it suddenly crystallized. Van Orman and his colleagues tried to reproduce this process using computer models of the planet's interior.
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These calculations unexpectedly showed that the inner core of the Earth should not exist. It turned out that the process of crystallization of its rocks is very different from how water and other supercooled liquids behave - this requires a huge temperature difference, more than a thousand kelvin, and an impressive size of a "speck of dust", whose diameter should be about 20-45 kilometers.
As a result, two scenarios are most likely - either the core of the planet should have frozen completely, or it still had to remain completely liquid. Both do not correspond to reality, since the Earth really has an inner solid and an outer liquid core.
In other words, scientists do not yet have an answer to this question. Van Orman and his colleagues suggest that all geologists on Earth think about how a large enough "piece" of iron could form in the planet's mantle and "sink" into its core, or find some other mechanism that would explain how it split into two parts.