Earth hit by more asteroids in past 290 million years

The number of asteroids hitting Earth and the moon have increased over the past 290 million years, research suggests.

Scientists turned to craters on the moon for more precise answers about the quantity of asteroid collisions, as both are struck in the same proportions over time but the moon’s craters do not suffer damage like Earth’s.

Before now, researchers used Earth’s craters in their studies and radiometric dating of the rocks, but many assumed early craters were worn away by erosion and other processes over time.

“It became clear that the reason why Earth has fewer older craters on its most stable regions is because the impact rate was lower up until about 290 million years ago,” said William Bottke, paper co-author and asteroid expert at the Southwest Research Institute.

Using thermal data and images collected by Nasa, a group of scientists from the University of Southampton, the University of Toronto and the Southwest Research Institute determined the age of lunar craters and calculated that the impact rate had grown 2.6 times over the past 290 million years.

“Proving that fewer craters on Earth meant fewer impacts – rather than loss through erosion – posed a formidable challenge,” said Dr Thomas Gernon, associate professor in earth science at the University of Southampton, and co-author of the study published in the Science journal.

Researchers are unable to explain the reason for the jump in impact rate, but suggest it may be related to debris created as a result of large collisions in the main asteroid belt between Mars and Jupiter.

The findings also strengthen the theory that asteroids contributed to mass extinctions on Earth, particularly dinosaurs.

“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,” Dr Gernon added.