The number of asteroids pummeling the ancient Earth jumped dramatically around 290 million years ago, according to scientists studying the Moon. By looking at Moon craters they discovered that during this period the number of asteroid impacts on both Earth and the Moon increased by two to three times.
It is hard to know how many asteroids impacted Earth at any given time due to erosion, so an international group of scientists looked at impacts on the Moon, which is hit by asteroids at the same rate as the Earth over time. They used data from NASA’s Lunar Reconnaissance Orbiter to determine the age of lunar craters, and from this they could work out how many asteroids impacted Earth at different periods in its history.
This oddly relaxing video shows one billion years of moon impacts condensed into one minute, with a soundtrack in which larger impacts produce deeper and louder notes. The background drone was created by converting the elevation of the Moon’s surface into a sound wave:
“Our research provides evidence for a dramatic change in the rate of asteroid impacts on both Earth and the Moon that occurred around the end of the Paleozoic era,” Sara Mazrouei, Department of Earth Sciences at University of Toronto and lead author of the study, said in a statement. “The implication is that since that time we have been in a period of relatively high rate of asteroid impacts that is 2.6 times higher than it was prior to 290 million years ago.”
290 million years ago was around about the end of the Paleozoic era, a time of dramatic change on the Earth in terms of geology, climate, and evolution, when life began to diverge into the ancient forebears of mammals, reptiles, and birds. After this came the time of the dinosaurs at around 250 million years ago, and the high rate of asteroid impacts is very likely to have played a role in the extinction of the dinosaurs, who “as a species were particularly vulnerable to large impacts from the get-go, more so than earlier animal groups,” according to Thomas Gernon, Associate Professor in Earth Science at the University of Southampton and a co-author of the study. “It’s perhaps fair to say it was a date with destiny for the dinosaurs — their downfall was somewhat inevitable given the surge of large space rocks colliding with Earth.”
Scientists had noticed that they found relatively few impact craters on Earth from asteroids that collided with the planet between 290 million years ago and 650 million years ago, but they previously believed that this was due to the craters being eroded. This new research suggests that this is not the case — there are fewer impact craters from this period because there were fewer asteroids. It is not yet known why the rate of asteroid impacts fluctuates so much, but it could be that large collisions took place in the asteroid belt between Mars and Jupiter 300 million years ago, creating debris which impacted Earth.