Asteroid Parade Created Ancient Hell on Earth

A parade of asteroids that struck our planet 4.5 billion years ago created an ancient hell on Earth, reshaping the surface and altering its topography, according to a team of researchers.

Published in the journal Nature, researchers from the Southwest Research Institute in Boulder, Colo., used a computer model to figure out just how many asteroids pummeled early Earth.

Earth is approximately 4.5 billion years old, but scientists only rarely find rocks that were formed more than 3.8 billion years ago. According to their Late Heavy Bombardment model, these researchers suggest that a barrage of asteroids destroyed these ancient rocks.

"It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish," lead author Simone Marchi told Space.com.

The exact timing and magnitude of the impacts that smashed Earth during the Hadean Era - the first 500 million years of Earth's existence - are unknown. To get an idea, Marchi and his colleagues looked at the Moon, given that its heavily cratered surface could provide a picture of the bombardments Earth experienced all those years ago.

"We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold, delivered to Earth as a result of these early collisions, and the amounts of these elements tells us the total mass accreted by Earth as the result of these collisions," Marchi explained. Previous research indicates that about 0.5 percent of Earth's present-day mass came from asteroid collisions.

According to the model, about one to four giant impacts 1,000 kilometers (600 miles) wide struck the planet over 4.2 billion years ago, along with three to seven smaller impacts exceeding 500 kilometers (300 miles) in width. Marchi adds that the planet only became inhabitable after these events.

The study suggests that some of the larger asteroids were 3,000 kilometers (1,860 miles) across.

And in Marchi's mind, according to The Space Reporter, there is no doubt that these series of collisions dramatically affected Earth's surface. The planet's crust was "excavated, mixed, and buried" as a result of the meteor storm, he said.

"At 1,000 kilometers, the effects would be so wide the planet would probably be completely resurfaced with material from the mantle," Marchi said.

This would mean "episodes of complete sterilization of Earth," he added.

According to the researchers, the only thing that could have survived these conditions were heat-resistant bacteria.

Commenting on the study, Henry Melosh, a geophysicist at Purdue University in West Lafayette, Ind., said via NDTV: "This paper shows the way for what will probably become a new thread in research on the environment and geology of the early Earth."