The bombing consisted of 30 to 60 times more material than the disastrous asteroid that killed the dinosaurs.

Researchers have come to the surprising discovery that some 800 million years ago, Earth was ravaged by a shower of asteroids. This is evident from thorough research into the… moon. The bombing must have been anything but tender. For example, the asteroid rain may have consisted of about 4-5 × 1016 kg of space stones. That’s about 30 to 60 times more mass than the disastrous asteroid impact that heralded the end of the dino era.

Moon
It is believed that once every 100 million years, Earth is struck by a massive asteroid. However, traces of this can hardly be traced. “We hardly find any impact craters from before 600 million years ago,” researcher Kentaro Terada tells Scientias.nl. “This is partly due to large-scale ice ages and certain breakdown processes that have permanently erased traces left behind.” Researchers decided to aim their arrows at the moon in order to reveal whether the Earth was plagued by space fragments in the distant past. “We actually used the moon as a ‘mirror’ for Earth,” says Terada. Any swarm of objects that gets close enough to hit the moon is likely to harbor Earth. And so research on the moon can provide insight into the distant past of our planet. “There is almost no erosion on the moon,” Terada continues. “This has preserved features of possible impacts on the moon.”

Craters
Using the Terrain Camera (TC) on board the Japanese spacecraft Kaguya, the researchers decided to determine the age of 59 lunar craters. All these craters are at least 20 kilometers in diameter. For example, the researchers examined the well-known impact crater Copernicus – which has a diameter of about 93 kilometers – and the surrounding small craters. An interesting conclusion then followed. Because the findings show that eight – and possibly even seventeen – of the 59 craters formed about 800 million years ago.

Image: Osaka University

Assuming that the same asteroid shower that bombarded the moon would also hit Earth, the researchers calculated that 40 trillion to 50 trillion tons of space debris would have hit our planet. As mentioned, this is about 30 to 60 times more material than the disastrous asteroid that killed the dinosaurs. However, the impact of the asteroid rain on young Earth is unknown. “We do not know whether this rock shower has damaged the Earth’s environment or promoted the evolution and diversity of life,” said Terada when asked. “The findings from our study do suggest, however, that the flow of extraterrestrial biological elements may have influenced the marine biogeochemical cycle.

Ryugu and Bennu
But that is not even the only surprising thing. Given the age of the asteroid rain, the researchers suggest that there may be a link between the bombing and the asteroid Eulalia that was formed some 830 million years ago. “Eulalia is considered to be the parent body of C-type asteroid, such as Ryugu and Bennu that are currently being studied by Hayabusa-2 and OSIRIS-Rex,” said Terada. “Ryugu and Bennu both consist of countless pieces of rock that have melted together under the influence of gravity. This is irrefutable proof that they have experienced a catastrophic disturbance of the parent body. And such a catastrophic disturbance of the parent body underlies the asteroid shower. It means that there may also be a connection between Ryugu and Bennu and the cosmic impacts on the Earth and the Moon. So remnants of that impact may still be near Earth. Whether there is indeed a connection between the two asteroids and the impacts in the Earth-Moon system, future research will show. Namely, samples from both Ryugu and Bennu will be taken back to Earth, after which the material will be thoroughly studied.

More about Ryugu and Bennu

Ryugu and Bennu are two asteroids that are currently undergoing thorough research. For example, scientists are comparing the two asteroids to gain more insight into the asteroid population in general. To date, Bennu and Ryugu appear to have quite a few similarities. They have a similar shape, are extremely dark and covered with large boulders. But there are also differences. For example, Ryugu contains much less water than Bennu. And researchers are currently unable to explain that. In the coming years we will learn a lot more about Ryugu and Bennu. Both Hayabusa 2 and OSIRIS-REx will return to Earth in a few years to deliver material they have collected on the asteroids.

The findings from the study provide important new information. Terada therefore emphasizes the importance of research into former impacts on Earth. “By knowing the past, we can also predict the future,” he underlines. Moreover, we are now gaining an ever better picture of the history of the earth and what our planet has already endured in the past.

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