More gigantic asteroids hit early Earth than expected

Massive asteroid impacts in Earth’s distant past are nothing new. Anyone that knows anything about dinosaurs knows that these space rocks were involved in their demise. 

Scientists have long been aware that enormous asteroids – larger than 10 kilometers in diameter – have pummelled the Earth. In a recent study, experts investigated how often large asteroids hit our planet in the past, and they found something shocking.  

“We have developed a new impact flux model and compared with a statistical analysis of ancient spherule layer data. With this approach, we found that current models of Earth’s early bombardment severely underestimate the number of known impacts, as recorded by spherule layers,” explained Dr. Simone Marchi of the Southwest Research Institute.

“The true impact flux could have been up to a factor of 10 times higher than previously thought in the period between 3.5 and 2.5 billion years ago. This means that in that early period, we were probably being hit by a Chicxulub-sized impact on average every 15 million years. Quite a spectacle!”

Extraterrestrial bodies like the Moon show obvious scars from asteroid impacts. On Earth, the signs of ancient collisions are masked by the atmosphere, weathering and other features. 

There is one sure sign of a past impact from an asteroid – little rocks called spherules. These are formed when the molten rock from a collision is thrown into the air and then rain back to earth where they become embedded in other stones. The more of these spherules found, the larger an impact.     

Scientists are interested in asteroid impacts on Earth because they could possibly explain the development of our atmosphere. 

Furthermore, it is possible that an asteroid was important for the beginning of life on Earth. So far, the scientists claim, the consideration of asteroids in our understanding of life on Earth has mostly been ignored. Perhaps this research will open a new chapter in our understanding of the history of our planet. 

“As we deepen our understanding of the early Earth, we find that cosmic collisions are like the proverbial elephant in the room. They are often neglected as we lack a detailed knowledge of their number and magnitude, but it is likely these energetic events fundamentally altered the Earth’s surface and atmospheric evolution,” said Dr. Marchi.

The research will be presented at the Goldschmidt Geochemistry Conference.

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By Zach Fitzner , Earth.com Staff Writer