Perhaps the early Earth had no plate tectonics or magnetosphere, and in order to acquire them, the planet had to endure powerful meteor impacts.
The warmth of the earth's interior sets in motion the plates of the earth's lithosphere and makes our planet restless and alive. Whether such a thing happened at the earliest stage of the Earth's existence, in the katarchea (between 4 and 4.6 billion years ago), is still unknown: too scant geological evidence of that era has survived to our time. However, some works show that the early Earth could have been covered with solid solid crust, and plate tectonics did not exist on it until 3.5 billion years ago.
This - as yet controversial - position is shared by the authors of a new article presented in the journal Nature Geoscience. Craig O'Neill and his colleagues from Australia and the United States wondered what split the Earth's lithosphere and set the continents in motion. The fact is that between 4.1 and 3.6 billion years ago, the planet, like other bodies of the inner solar system, experienced a period of Late Heavy Bombardment and was subjected to countless and heavy blows.
Scientists have modeled the Earth of the Katarchean era - with a solid single lithosphere, superheated from the inside - and examined the results of collisions with it of large protoplanetary bodies up to 1,700 km across. “Our results show that powerful meteorite impacts could have caused the Earth's solid surface to sink into the mantle,” says Professor O'Neill. We are talking about subduction - the departure of the lithospheric plates of the oceanic crust under the edges of other plates. It is subduction that provides tectonics, breaking down old plates, triggering earthquakes, volcanoes and the growth of new mountains.
However, according to scientists, the impact of the meteorite bombardment was far from limited. It also affected the outer semi-liquid core of the planet, increasing convective currents in its molten material. The beginning of active mixing of the iron-nickel alloy could lead to the appearance of a global magnetic field - another key condition for life on Earth.
Sergey Vasiliev
