The number of asteroid collisions with the Earth and Moon has increased by up to three times since the age of dinosaurs, over the past 290 million years.
These new findings challenge our knowledge of the Earth’s history. The major study involving the University of Southampton found that asteroid collisions have almost tripled in this time.
Studying the Moon for clues into asteroid impacts
Scientists have previously tried to understand the rate of asteroid collisions with Earth for decades, by studying the Earth’s craters and dating the rocks around them. However, many experts assumed that the earliest craters have worn away due to geological processes such as erosion. The new study has shown that actually we can learn a lot about the history of the asteroid collisions with Earth by studying the Moon. This is because both the Earth and Moon are hit in the same proportions over time, and the Moon is immune to many of the processes which destroy Earth’s craters, such as plate tectonics.
William Bottke is an asteroid expert at the Southwest Research Institute in Boulder, Colorado and the co-author of the paper. He explained: “The only obstacle to doing this has been finding an accurate way to date large craters on the Moon.”
The team studied the surface of the Moon using NASA’s Lunar Reconnaissance Orbiter (LRO)’s thermal data and images to determine the ages of the Moon’s craters. The Diviner, which is the NASA spacecraft’s thermal radiometer, showed that heat is radiating off the Moon’s surface, with larger rocks giving off more heat than the fine lunar soil.
The implications for the Earth’s history
This work led to the discovery that the rate of crater formation from asteroid collisions has been two to three times higher over the last 290 million years than in the previous 700 million years. This could have implications for studying the Earth’s history, for example it could illuminate information about extinction events. Although extinction events could have many causes, the team explain that asteroid impacts could have played a major role.