About 800 million years ago, a collision in the main asteroid belt may have triggered a rain of debris towards Earth, Mars and the Moon. Researchers propose this scenario to explain an unusual concentration of impacts and global changes.
The event would be linked to the disruption of an ancient parent body of the Eulalia asteroid family. This collision would have produced many carbon-rich fragments. Some of them would then have been slowly moved towards an unstable orbital zone.
The researchers used numerical models to track the evolution of these fragments. Their simulation takes into account the gravity of the planets, but also the Yarkovsky effect. This phenomenon gradually modifies the orbit of a small asteroid under the effect of heat received and re-emitted.
According to calculations, about three-quarters of the fragments would have ended up reaching a resonance with Jupiter. This configuration would have favored their movement into the region occupied by the inner planets. A bombardment would then have occurred over a period lasting up to 150 million years.
The Moon provides the most visible clues. Several studies have already indicated a major increase in lunar impacts around that time. The age of some craters and impact-produced glasses corresponds to this period.
The model notably links the event to the formation of the Copernicus crater, even if this interpretation will need to be compared with other data.
On Earth, the period coincides with major changes in the biosphere. It is possible that some impacts disrupted the climate or ecosystems, but the link remains difficult to prove. Erosion and tectonics have indeed erased most of the ancient terrestrial craters.
Mars may also have experienced consequences. The authors indicate that the impacts may have contributed to a phase of volcanic activity.
This study shows that a collision in the asteroid belt can influence the history of several planets. Future lunar and Martian missions could provide additional samples to verify if this rain of debris actually hit the inner Solar system.