Traces Of An Ancient Asteroid Shower Found On The Moon
Approximately 800 million years ago, the Earth and Moon experienced a meteor bombardment, according to an article in Nature Communications. Scientists came to this conclusion based on the analysis of images obtained by the Japanese probe "Kaguya."
According to researchers, the total mass of the fragments was 30-60 times greater than that of the meteorite, whose fall could have caused the extinction of the dinosaurs.
According to modern ideas, about 3.9 billion years ago, the inner planets intersected with a dense cloud of asteroids and other celestial bodies, surviving an incredible Late heavy bombardment. It is believed that this is when most of the known craters on the moon appeared, and most of the water, and possibly simple organic compounds, were deposited on the Earth during this period.
After that, the frequency of collisions with large bodies decreased markedly — our planet has experienced only a few such events in the past three billion years. Their traces are actively studied by geologists, but research is very complicated by the fact that The Earth's surface is updated by erosion and other processes. Therefore, scientists often turn to the moon in search of craters, since it is very close and has likely been subjected to similar impacts, but it does not have water flows and strong winds.
Astronomer Kentaro Terada from Osaka University, along with colleagues, analyzed images of the moon's surface obtained by the Kaguya orbiting probe. The researchers analyzed 59 craters with a diameter of 10 to 20 kilometers, which, judging by their morphology, should have been formed relatively recently. By plotting the size distribution of young craters within larger and older ones, the authors found that eight of them, including the Copernicus crater (samples from which were brought to Earth by the Apollo astronauts), appeared almost simultaneously.
Based on Radiometric Dating of the regolith and glass balls formed when meteorites fell, the authors concluded that the craters appeared on the surface of the moon about 800 million years ago as a result of the bombardment.
Besides, such a bombardment would also have to take place on the ground at the same time. According to researchers, the total mass of the debris was at least 40-50 trillion tons, which is ten times heavier than the Chicxulub meteorite, whose fall, according to one version, led to the extinction of the dinosaurs.
The authors suggest that the meteorites could be chondrites of the Eulalia family — a minor planet whose progenitor collapsed about 830 million years ago and became the source of a group of asteroids in the main belt between Mars and Jupiter. This hypothesis is supported by the fact that the concentration of phosphorus in the marine sedimentary rocks of the Earth at that time was significantly higher than in previous geological eras. This is well explained by the fall of a large number of chondrites, which have become an additional source of an important element for life.
Earlier, scientists doubted the reality of the Late heavy bombing. Computer simulations have shown that evidence of the massive bombardment that the inner Solar system was subjected to almost 4 billion years ago is not reliable enough.