By investigating the formation ages of lunar craters, a team of researchers led by Osaka University, Japan, have determined that 800 million years ago the Earth-Moon system suffered a colossal blow.
Up to 50 quadrillion (that’s five followed by 16 zeros) kilograms (110 quadrillion pounds) of meteoroids (small rocky bodies in space) plunged into the two celestial objects. That is roughly 60 times the amount of material involved in the Chicxulub impact – the asteroid event that sealed the fate of non-avian dinosaurs 66 million years ago.
Asteroid events on the scale of Chicxulub are predicted to strike Earth every 100 million years or so. However, craters from such an impact that occurred more than 600 million years ago will have been wiped from the planet due to erosion, volcanism, and other geologic processes. Therefore, to study impacts from this timeframe astronomers turn to our orbiting body – the Moon.
Using images captured by the Japanese Space Agency’s (JAXA) lunar orbiter spacecraft Kaguya, the team studied 59 craters greater than 20 kilometers (12.4 miles) in diameter. As described in a study published in Nature Communications, the density of the surrounding smaller craters formed from ejecta could then be used to approximate their ages. Of the 59 under investigation, the researchers discovered that eight formed simultaneously, the first time this has been recorded.
The culprit of the impacts is a gigantic 100-kilometer-wide (62-mile-wide) asteroid. Its fragments rained down on the Earth-Moon system as smaller meteoroids bombarding the planet and its companion. Further analysis showed that the parent carbon-containing asteroid was no ordinary rock – it belonged to the Eulalia family of asteroids – one of the five families that most asteroids can be traced back to.
In fact, asteroid Ryugu, a sample of which is currently on its way back to Earth, is thought to be part of the same family. It could even be a fragment left behind from this colossal asteroid shower 800 million years ago.
“Our research results have provided a novel perspective on earth science and planetary science,” lead author Professor Kentaro Terada of Osaka University said in a statement. “They will yield a wide range of positive effects in various research fields.”