Earth May Be Struck by Large Asteroids More Often Than Scientists Once Believed

Earth might be struck by large asteroids more frequently than scientists had once believed, according to the results of a new study based on satellite imagery of ancient impact sites.

Life on Earth has been forced to endure a series of cataclysmic extinction-level disasters throughout the course of its 3.8 billion-year history. These devastating die-offs vary in size from global catastrophes to localized events, and can result from slow shifts in climate, or devastating one-off events, such as the asteroid strike that killed off the dinosaurs some 66 million years ago. 

Earth’s mantle still bears the scars from many of these devastating impacts. However, over time, the resulting craters have been eroded by the passage of wind and water, making it harder for scientists to reconstruct, and understand the nature of the brutal events. 

Thankfully, scientists are still able to characterise ancient asteroid strikes by observing nearby solar system objects, and comparing the remains of craters on Earth to those of similar craters found on the moon. There, the lack of an atmosphere preserves impact sites in a near pristine condition, allowing scientists to get a better idea of the energy transferred by a strike.

Based on this data, scientists estimate that Earth is hit by a colossal 1 km-wide asteroid once every 600,000 to 700,000 years. However, according to the results of a new study, the impacts that have scarred Earth’s surface over the past million years may have been even more violent than previously thought.

The research was conducted by a team of scientists led by James Garvin, the chief scientist at NASA’s Goddard Space Flight Center. According to a post on the journal Science, the scientists used thousands of hyper-detailed images collected by a fleet of Earth observation satellites to create 3D maps of four crater sites that were formed in the past million years.

Over the course of the study, the researchers ran thousands of tests on the 3D crater maps using an algorithm designed to detect circular formations on the surface of Mars. 

The algorithm regularly detected the presence of rim-like structures kilometers beyond the accepted rims of four of the craters. These previously undetected features often doubled the size of the known impact sites, which in turn suggests that the collisions that created them were far more energetic than previously believed, and were likely created by impactors that were over 1 km wide. 

According to Science, if the new formations are indeed the true crater rims as Garvin believes, then the explosions that created them would have been “10 times more violent than the largest nuclear bomb in history.”

Whilst they pale in comparison to the devastation wrought by the Chicxulub asteroid that led to the extinction of all land-dwelling dinosaurs, the smaller strikes would still have been capable of altering the climate, and triggering localized extinctions. 

If true, the discovery would indicate that Earth is struck by massive asteroids more frequently than was previously believed to be the case. However, some scientists doubt that the newly identified structures are real crater rims, instead suggesting that they may have been formed from debris that was thrown out by the violence of the impacts.

Whilst Garvin doubts that a debris ring would still be visible after all this time, he also noted that the detection of the ring structures hadn’t catagorically “proven anything,” and that fieldwork would be needed to confirm or disprove that they are in fact impact rims.

In the meantime, space agencies across the globe are working together to scan the heavens for potential threats, and are actively developing planetary defence strategies to deflect incoming asteroids.

Just last year NASA’s DART mission rendezvoused and collided with a solar system asteroid, successfully altering its path through space.

It is inevitable that another large asteroid will find itself on an intercept course with Earth at some point in the future. Missions like DART are the first step on the road to developing a fully fledged asteroid defence capability that could one day prevent the extinction of our species.

Anthony is a freelance contributor covering science and video gaming news for IGN. He has over eight years experience of covering breaking developments in multiple scientific fields and absolutely no time for your shenanigans. Follow him on Twitter @BeardConGamer

Image Credit: Shutterstock, Dima Zel