A recent analysis of lunar craters carried out remotely suggests that the number of asteroid impacts has considerably increased over the last 300 million years. Details of the study were published in Science.
The Earth and Moon have been struck by asteroid collisions on a similar level. Unfortunately due to erosion on our planet, researchers struggle to precisely date these asteroid impacts. However there is no erosion process on the moon. As a result, we can estimate the rate of terrestrial asteroid impacts by precisely dating lunar impacts. This is what a team of researchers from the University of Toronto, Canada are currently suggesting.
These researchers used a new technology which allows them to precisely date lunar craters remotely. In order to do this, scientists used thermal data and images collected by NASA’s Lunar Reconnaissance Orbiter (LRO). Their idea is that when a crater forms after an impact, the dug up rocks are positioned around the crater. Overtime these rocks transform into regolith (lunar dust), after being struck by micro meteoroids. It is therefore assumed that young craters on the moon are surrounded by large rocks, while the oldest are surrounded by dust.
Asteroid impacts with Earth becoming increasing common
Thanks to this technique, researchers have estimated a rate of asteroid collisions over the last billion years measuring craters with a diameter more than 10 km. Their results show that the impact rate on Earth seems to have multiplied by 2.6 from around 290 million years ago, a few million years before the arrival of the dinosaurs. The researchers also note the almost complete absence of terrestrial craters more than 650 million years old. Researchers believe this suggests a “massive erosion event on a global scale, at a time when our planet was covered with ice.” Sub-glacial erosion could have eliminated kilometers of material – enough to erase most of the existing impact craters.
If this research is confirmed then it would contradict what has previously been believed. Theoretically, the number of asteroid collisions should decrease as the debris left behind after the formation of the solar system reduces. However these results seem to suggest that the number of asteroid impacts have increased over the last 300 million years.
Sara Mazrouei, the leading author of this study believes this higher rate of asteroid impacts could be due to a rupture in the main asteroid belt. Mazrouei explains that “When two large asteroids collide, they produce a swarm of fragments close to the impact site. These eventually move on to Earth-crossing orbits and a few end up hitting the Moon and Earth.”