Giant Asteroids In The First Epochs Of The Earth's Existence Fell On It Every 10-15 Million Years
Computer simulations have shown that large asteroids fell on the Earth's surface every 10 or 15 million years in the first epochs of its existence. Previously, scientists assumed that this happened ten times less often. They told about the results of the study at the Goldschmidt Geochemical Conference.
Planetary scientists believe that the Earth and other planets of the Solar system in the early stages of existence were constantly bombarded by asteroids and comets. This period, which began about 4.1 billion years ago and ended after 400 million years, is called the "late heavy bombardment." Then almost all the large craters are known to science on Earth, Mercury, Mars, and the Moon appeared. Subsequently, asteroids almost stopped falling on the planets of the Solar system.
Simone Marchi from the Southwest Research Institute (USA) and his colleagues found out that the frequency of massive asteroid falls can be fairly accurately estimated by the number of spherules in ancient sedimentary rocks. That is what scientists call small spherical particles that are formed as a result of the melting of rocks of a celestial body at the time of its fall to the planet.
If the fallen asteroid reached 10-15 kilometers in diameter, then the spheres generated by them will be scattered virtually throughout the entire territory of the globe. By the concentration of these particles in various rocks, it is possible to calculate the frequency with which celestial bodies fell to the Earth.
Based on this idea, Marchi and his colleagues measured the concentration of spherules in the oldest rocks of several regions of the planet. Based on this data, they created a computer model of the planet which describes the history of its collisions with asteroids.
It showed that in the first billion years after the "late heavy bombardment", many more asteroids fell on our planet than scientists thought.
Large celestial bodies, similar in size to the asteroid that destroyed the dinosaurs 66 million years ago, fell to Earth not every 100-150 million years but about ten times more often.
Scientists suggest that this significantly affected both the appearance of the planet and the chemical composition of its atmosphere, as well as the evolution of the first living organisms on the planet.
That is supported, as suggested by Marchi and his colleagues, by the fact that the oxygen concentration in this era increased and fell sharply several times. That could greatly affect the life of the first microbes and the nature of their development.