Asteroids, Meteors Smashed Into Earth 10 Times More Often Than Previously Thought

New research has revealed that Earth was bombarded with 10 times as many objects from space, such as meteors and asteroids, as previously believed during its early history.

These frequent violent collisions may have played an important role in the geological and atmospheric evolution of our planet.

The authors of the paper, published in the journal Nature Geoscience, say the period when the pelting of Earth with meteors and asteroids increased was between 3.5 billion and 2.5 billion years ago.

"We have derived a new model for the bombardment of the ancient Earth, and
found that collisions were up to a factor of 10 more frequent than previously thought in the time frame 3.5-2.5 billion years ago," Simone Marchi, the paper's lead author and a scientist at Southwest Research Institute in Boulder, Colorado, told Newsweek.

The research could challenge the perception that scientists have of our planet's development.

Not only was the bombardment of Earth by objects from space more frequent than scientists realized, but Marchi said some of these objects were also tremendous in size.

"We estimated that the Earth in this time frame was hit by asteroids six miles across or larger every 15 million years or so," he added, explaining that this is about the size of the asteroid that wiped out the dinosaurs around 66 million years ago. "Some of these impactors could have been up to 50 miles across."

While such impacts would eventually go on to be considered more destructive, these early bombardments could have been of vital importance in affecting Earth's chemistry and its atmosphere.

"The chemistry of the impactor material is very different from that of the surface of the Earth, and therefore has the potential to alter the chemistry of the atmosphere," said Marchi, who is also the author of the book Colliding Worlds, which explains how cosmic encounters can shape planets and life itself.

"In our work, we looked at how impactor materials could have affected the concentration of atmospheric oxygen," Marchi said. "The chemistry of impact materials is such that they readily combine with oxygen, removing it from the atmosphere.

"So, a large flux of impacts could have potentially delayed the rise of atmospheric oxygen."

The team of researchers reached the conclusion that Earth suffered 10 times as many impacts from space as previously believed by measuring so-called "impact spherules" in the geological record.

Impact spherules form when asteroids crash into Earth and vaporize rock. This vapor rises through the atmosphere and cools, eventually falling back down to the planet as tiny particles that are preserved in rock.

Scientists have used impact spherules for many years to investigate the details of asteroid strikes, but what Marchi and his team discovered was that current models of just how many impact spherules should form after an impact suggest that asteroid and meteor strikes were much more common than we had realized.

The early solar system was a much more violent place than it is today and Earth was in the firing line. Impacts were particularly prevalent during a period known as the late heavy bombardment, about 4.5 to 3.8 billion years ago, when failed planets and smaller asteroids slammed into the planets of the solar system.

Marchi, who told Newsweek he was inspired to conduct the research by his fascination with the evolution of the ancient Earth and how this was shaped by cosmic collisions, said the next step for the research was to examine ancient terrestrial rocks to find out more about the signatures of these ancient catastrophes.

Earth's Early History
In an illustration, the young Earth is bombarded with asteroids. New research suggests that these impacts were 10 times as common as previously believed. Goddard Image Lab/NASA