A team of planetary researchers from Japan has demonstrated that a 100-km asteroid was disrupted 800 million years ago (Tonian period of the Neoproterozoic era) and that at least 4*1013 tons of meteoroids — approximately 30-60 times more than the dinosaur-killing Chicxulub impact — must have plunged into the Earth. “Understanding meteor bombardment of Earth is an issue of both great scientific interest and practical importance because impacts are potentially hazardous to our planet,” said lead author Professor Kentaro Terada from the Department of Earth and Space Science at Osaka University and colleagues. “Since the Cambrian biodiversity explosion, mass extinction events have occurred at least five times, and extraterrestrial impacts are considered a potential cause of some of them.”
Using data from the Terrain Camera onboard JAXA’s Kaguya lunar orbiter, Professor Terada and co-authors investigated the formation ages of 59 lunar impact craters with a diameter of approximately 20 km. They found that eight of these craters, including the 93-km-wide Copernicus crater, were formed simultaneously. “Since the Earth-Moon system has been co-evolving over 4.5 billion years, this new finding provides us with crucial insight into the Earth-Moon system because asteroid showers must have occurred not only on the Moon but also on the Earth,” they said.
“Based on the probability ratio of collisions with the Earth and the Moon of 23:133, we conclude that a mass of 4-5*1013 tons must have collided successively on the Earth at 800 million years ago, i.e., immediately before the Cryogenian period, which was an era of great environmental and biological changes.”
The scientists think that this asteroid shower was caused by the disruption of the parent body of the C-type asteroid Eulalia.
“Our research results have provided a novel perspective on earth science and planetary science,” Professor Terada said.
“They will yield a wide range of positive effects in various research fields.”