Researchers believe the early Earth was hit by up to four asteroids that had the ability to kill off any existing life and resurface the planet.

After the Earth was formed 4.5 billion years ago the solar system is believed to have been bombarded by asteroids. The moon and mercury still have visible scars from the events, but melting and reforming of the Earth's crust have made it nearly impossible to determine its impact history, Nature reported. The team looked at impact craters on the moon and used a computer model to calculate how many asteroids hit our home planet. The findings were published in Nature.

"This paper shows the way for what will probably become a new thread in research on the environment and geology of the early Earth," Henry Melosh, a geophysicist at Purdue University in West Lafayette told Nature.

The model suggest the biggest asteroids to hit Earth were about 3,000 kilometers across; between one and four of them would have been a minimum of 1,000 kilometers across. Between three and seven of the impacts are believed to have been from asteroids 500 kilometers in width. These would have hit between 4.2 and 4.3 billion years ago. A 10-kilometer-wide asteroid was enough to kill the dinosaurs, so the impact of these giant rocks would have been immense.

 "At 1,000 [kilometers], the effects would be so wide the planet would probably be completely resurfaced with material from the mantle," Melosh said. This would lead to "episodes of complete sterilization of Earth," he said.

The simulations predicted a spike is asteroid impacts about 4.1 billion years ago, which is consistent with the oldest-known zircon samples. This suggests zircons could have been created when large areas of the Earth's were buried by the devastating asteroid impacts.

This theory "has a lot of merit," Oleg Abramov, an astrogeologist at the US Geological Survey told Nature.