The Earth and Moon have had many more asteroid impacts since the age of the dinosaurs

The number of asteroids that have collided with the Earth and the Moon has tripled over the past 290 million years, according to new research from the University of Southampton

The number of asteroids that have collided with the Earth and the Moon has increased up to three times over the past 290 million years (about 7% of the Earth's total age), according to new research from the University of Southampton. These findings, published in Science, challenge the previous understanding of Earth's vulnerability history.

Scientists have been trying to understand the rate of asteroids hitting Earth for decades, usually by studying the craters and surrounding rock formations. The problem however is that many experts assumed that the older craters were eroded over time due to other geological processes.

However, researchers have now found that we can learn a lot about Earth's history by studying the Moon, because both celestial bodies are affected in the same proportions over time. Furthermore, the Moon is immune to many of the processes, such as plate tectonics, responsible for destroying the ancient craters on Earth.
"The only obstacle to doing this has been finding a way to accurately measure the age of large craters on the Moon," said William Botke, an asteroid expert at the Southwest Research Institute in Boulder, Colorado, and a co-author of the paper.

The team examined the moon's surface using thermal data and images collected by NASA's LRO spacecraft to determine the ages of the moon's craters. The thermal device on the spacecraft, known as Diviner located on LRO compiled the heat radiation map of the moon. Larger rocks radiate more heat compared to fine grained soil. Another author of the article, Rebecca Gent, a planetary scientist at the University of Toronto and the Institute of Planetary Sciences in Tucson, Arizona, calculated the rate of disintegration of lunar rocks and the filling of the ground with them, and discovered a connection between the amount of large rocks near a crater and the age of the crater. Using Gantt's technique, the team calculated the ages of all lunar craters that are less than a billion years old.

Many young craters on the Moon and Earth

Younger craters tend to be more covered in ash than older craters. This happens because rocks ejected by an asteroid impact have been eroded under a constant shower of tiny meteorites.

When team members compared the ages and numbers of craters on the Moon to those on Earth, they made the astonishing discovery that they are very similar, challenging the idea that Earth has lost so many craters. "This means that the Earth has fewer old craters in its stable regions not because it lapsed, but because the vulnerability rate was low 290 million years ago," Botka said.

Dr. Thomas Gernon, Associate Professor of Earth Sciences at the University of Southampton, and co-author on the study, said: "Proving that fewer craters on Earth means less vulnerability and not disappearance through erosion - posed a huge challenge."
The team's work led to the discovery that the crater formation rate during the last 290 million years was two to three times the average for the last 700 million years.

The reason for this jump in the vulnerability rate is unknown, but it could be related to large collisions that occurred more than 290 million years ago in the central asteroid belt between the orbits of Mars and Jupiter. Such events can create asteroid fragments that may reach the inner solar system.
The group's findings regarding the Earth have implications for the history of life - which was interrupted by major extinction events and the rapid development of new species. Although the extinction events could have many causes, the team notes that it is likely that an asteroid impact played a major role twice, initially when the dinosaurs spread across the Earth about 250 million years ago after a mass extinction, but their fate was also similar considering the wave of rocks crashing into the Earth's floor , concluded Gernon.

Editor's note: This study further reinforces the need for the establishment of a space watch, which will include systems to intercept asteroids that may collide with Earth.

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In the same topic on the science website:

• NASA is making progress in developing a spacecraft to divert asteroids from their orbits
• Asteroid impacts significantly changed the Earth's surface
• Asteroids lurk in the dark