Recent analysis of several lunar craters suggests that the Earth-Moon system suffered a particularly violent episode of bombardment 800 million years ago.
40 to 50 trillion metric tons of meteorites hit the Earth-Moon system 800 million years ago, study finds. It was 30 to 60 times the amount of material involved in the Chicxulub impact that precipitated the disappearance of non-avian dinosaurs 66 million years ago.
Our planet shows almost no signs of this trauma. The scars of this attack from the sky have indeed long since been erased due to erosion, volcanism and other geological processes. In fact, almost all traces of terrestrial bombardments that occurred more than 600 million years ago are no longer available . On the other hand, the Moon still bears some marks.
As part of recent work, published in the journal Nature communication , researchers from Osaka University (Japan) analyzed data from the Kaguya lunar orbiter of the Japanese Space Agency (JAXA). The team focused on studying 59 craters over 20 kilometers in diameter.
Specifically, it involved estimating the age of formation of these large craters by examining the density of craters from 0.1 to 1 km from diameter in their ejecta . Among them was the Copernic crater (93 km in diameter) and its 860 small surrounding craters. The density of the latter thus made it possible to determine the age of the largest crater.
Of this sample of 59 craters, the researchers determined that eight of them formed simultaneously about 800 million years ago.
Computer simulations attempting to reproduce these various impacts suggest that the culprit is none other than a gigantic asteroid 100 kilometers wide, some fragments of which would have rained down on the Moon. Others escaped this first obstacle, before finally crashing into the Earth.
Obviously not all of them have come into contact with our close system. Some probably ended up in the Sun, while others remained wisely in the asteroid belt, between the orbits of Mars and Jupiter.
Furthermore, further analysis showed that the parent asteroid belongs to the Eulalia asteroid family. The asteroid Ryugu, a sample of which is currently on its way back to Earth, would notably be part of the same family. Moreover, it would not be impossible that the latter is itself a fragment of this first parent asteroid .
According to this study, these cosmic impacts would therefore have hit the Earth and the Moon just before the cryogenic period, which extends from -720 million to -635 millions of years. It was during this period that our planet experienced its greatest ice ages . It is therefore not impossible that this cosmic bombardment has something to do with it.
Previous research has indeed suggested that the Chicxulub impact 66 million years ago released so much dust into the atmosphere that the sky darkened, eventually cooling the Earth.
We also know that 470 million years ago, another meteor shower also kicked up extraordinary amounts of dust, potentially triggering the Ice Age of the Earth. Middle Ordovician. However, this episode was probably much less impressive than the event that took place 800 million years ago.
