Artist's impression of the Earth between 3.5 and 2.5 billion years ago when asteroids the size of cities bombarded our planet. Credit: SwRI/Simone Marchi, Dan Durda

Ancient Earth Was Bombarded By Cataclysmic “City-Sized” Asteroids

Earth was not always as safe as it is today.

Scientists have found that Earth’s atmosphere filled with enough oxygen to support life as we know it about 2.5 billion years ago. And this happened, according to the hypothesis of astrophysicists from the Southwestern Research Institute of the United States, as a result of an aggressive attack on the Earth by powerful asteroids that bombarded our planet every fifteen million years in the Archean era.

The study also showed that the number of these impacts could be 10 times more than previously thought, and some of the bodies were on a scale comparable to a large modern-day city. Imagine the Earth being hit with several or even dozens of city-sized asteroids in short periods of time.

Did city-sized asteroids make Earth more hospitable for life?

It is precisely such destructive cataclysms, the researchers conclude, that were able to influence the geochemistry of the Earth, and, consequently, accelerate the development of life on our planet.

True, not all mysteries of nature are in a hurry to meet scientists an reveal their secrets. When it comes to asteroids, comets, meteorites, most of our questions remain unanswered. After all, most of the oldest craters have disappeared from the planet’s surface as a result of weathering and plate tectonics.

But, as you know, whoever is looking will always find something, including traces of asteroids. The fact is those vitreous particles – spherules, which are formed from rocks melted by an explosion, have been preserved in rocks for several billion years old.

A meteor crater in Arizona which formed as a result from an impact of a 50-meter meteor. When you consider that the bodies that hit Earth according to the new study were city-sized asteroids, where are the remains of these massive impacts? Credit: Dr Dale Nations, AZGS.
A meteor crater in Arizona which formed as a result from an impact of a 50-meter meteor. When you consider that the bodies that hit Earth according to the new study were city-sized asteroids, where are the remains of these massive impacts? Credit: Dr Dale Nations, AZGS.

The more similar particles are present in a particular cultural layer, the more powerful the catastrophe was. And, having analyzed the content of ancient sediments, the researchers were forced to admit that modern science clearly underestimated the scale of cosmic impacts.

It is quite possible, the authors of the scientific work state, that “it was the systemic torpedoing of the planet that radically changed the evolution of the earth’s surface and atmosphere.” The impacts of asteroids, in their view, should have reflected on the oxygen levels on our planet.

The fact that the saturation of the earth’s atmosphere with oxygen took place about 2.5 billion years ago was asserted long ago. But earlier, scientists believed that they are associated with the processes taking place in the bowels of the planet. But, as recent data have shown, a cosmic invasion could also be the cause of these global changes.

Given the importance of oxygen for the development of the Earth and life on it, the American authors summarize that its possible connection with asteroids is intriguing and deserves further study. But this, alas, has yet to be determined at the next stage of research. When you consider that the earliest signs of life on Earth are from about 3.5 billion years ago, was it a coincidence? Or did city-sized asteroids change our planet and gave simple life forms a boost?


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Sources:

EurekAlert. (n.d.). Early Earth was bombarded by series of city-sized asteroids. EurekAlert!
O’Neill, M. (2021, July 11). Early Earth Was Bombarded by Barrage of City-Sized Asteroids – Perhaps 10x More Huge Impactors Than Thought. SciTechDaily.
Phys.org. (2021, July 8). Early Earth was bombarded by series of city-sized asteroids.
Young, C. (2021, July 9). City-Sized Asteroids Hit the Earth More Frequently than Previously Thought. Interesting Engineering.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. My experience as a freelance writer began in 2018 but I have been part of the Curiosmos family since mid-2020. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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