About 800 million years ago the Earth and Moon survived the meteoritic bombardment, reported in an article in Nature Communications. To such conclusion scientists have reached based on the analysis of images obtained by the Japanese probe “Kaguya”. Researchers estimate, the total mass of the fragments was 30-60 times greater than that of a meteorite fall which could have caused the extinction of dinosaurs.
According to modern concepts, about 3.9 billion years ago the inner planets were crossed with a thick cloud of asteroids and other celestial bodies, having experienced the incredible power of the Late heavy bombardment. It is believed that it then appeared most of the known craters on the moon and on the Earth during this period was recorded most of the water, and perhaps simple organic compounds.
After that, the frequency of collisions with large bodies decreased markedly over the last three billion years our planet has experienced only a few such events. Their traces have been studied intensively by geologists, but research is very much complicated by the fact that the surface of the Earth is updated under the action of erosion and other processes. Therefore, scientists in search of craters often turn to the moon, as it is very close and likely were exposed to similar influences, but there are no water streams and strong winds.
Astronomer Terada Kentaro (Kentaro Terada) of Osaka University, together with colleagues analyzed images of the surface of the moon obtained by orbiting probe “Kaguya”. The researchers analyzed the 59 craters with a diameter from 10 to 20 kilometers, which, judging by their morphology, were formed relatively recently. Constructing the size distribution of young craters inside larger and more ancient, the authors found that eight of them, including Copernicus (samples of which were brought to Earth by the astronauts of the “Apollo”), emerged almost simultaneously.
Based on radiometric Dating of regolith formed by the fall of meteorites glass beads, the authors came to the conclusion that the craters appeared on the surface of the moon some 800 million years ago in the bombing. In addition, a similar bombing at the same time had to occur on Earth. Researchers estimate, the total mass of the wreckage was at least 40-50 trillion tons, which is ten times heavier than the meteorite Chicxulub, the fall of which, according to one version, led to the extinction of the dinosaurs.
The authors suggest that the meteorites could be the chondrites family Eulalie — a small planet, the progenitor of which about 830 million years ago collapsed and became a source of a group of asteroids in the main belt between Mars and Jupiter. In favor of this hypothesis is that the concentration of phosphorus in marine sedimentary rocks of that era were much higher than in the previous geological era. It is good is due to the fall of a large number of chondrites, which became an additional source of important for the life of the item.
Previously, scientists doubted the reality of the Late heavy bombardment. Computer simulations showed that the evidence of the massive bombing, which the inner Solar system was subjected to almost 4 billion years ago, not very reliable.