A new study has shown that Earth was hit harder by comets and asteroids than previously thought. This disrupted the formation of its atmosphere, and caused significantly lower levels of oxygen.
Researchers at Harvard University and Southwest Research Institute have created a new model that suggests Earth was struck by massive impacts approximately every 15 million years. This is about 10 times more than previously thought.
The Archaen eon is the time period in which comets and asteroids bombarded Earth. Some of these comets were larger than six miles across, researchers said.
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These massive space rocks landing on Earth more often than expected meant that oxygen levels were lower than they could have been. They were also lower than levels after the Great Oxidation Event, when oxygen levels increased significantly in the Earth’s atmosphere.

Earth was hit by comets and asteroids billions years ago, disrupting its atmosphere, and causing lower oxygen levels.

Earth was likely to be hit by a huge impact approximately every 15 million years, ten times more than previously thought.
The GOE enabled life to form and the planet to be forever altered by it.
These new findings could help scientists get a better picture of Earth’s origins and how it looks today.
In a statement, Nadja Drabon (co-author of the study, and an assistant professor at Harvard of Earth and Planetary sciences) stated that ‘free oxygen in the atmosphere was critical for any living being which uses respiration to generate energy.
“Without the accumulation oxygen in the atmosphere, we would probably not be here.”
Dr Laura Schaefer, co-author of the Stanford University study, said that late Archean bombardment by objects more than six miles in diameter would have produced enough reactive chemicals to completely consume low levels.
This pattern was consistent in evidence for so-called “whiffs of oxygen”, relatively rapid, but transient, increases in atmospheric oxygen that occurred approximately 2.5 billion years ago. We believe that the whiffs are broken down by impacts that removed oxygen from the atmosphere.
This is consistent with large impacts recorded in Australia’s Bee Gorge, Dales Gorge, by spherule-layers.

Some of these comets and asteroids were over six miles wide, causing an ‘oxygen sink’ that sucking most essential gas from the atmosphere.

After discovering impact spherules, which are tiny bits of ancient asteroids that remained on Earth after the collision that produced a vapor plume, the researchers were able come up with their findings.
After discovering that tiny bits of ancient asteroids particles remained on Earth following the collision that created the vapor plume, the researchers were able find their findings.
The spherules were shot into the young atmosphere but condensed when they returned to Earth.
Drabon said that impact spherules cannot be missed. However, Drabon explained that recent evidence has been provided ‘for additional impacts that have been found that weren’t recognized before’.
After the Earth’s atmosphere began to cool, it formed. It was largely composed of carbon dioxide and nitrogen.

However, the impacts began to slow down approximately 2.4 billion year ago and oxygen levels on Earth started rising again, resulting the Great Oxidation Event
Asteroids with a diameter greater than six miles would likely have caused an “oxygen sink”, sucking most of essential gas from the atmosphere.
However, the impacts began to slow down approximately 2.4 billion year ago and oxygen levels started to rise again, resulting into the GOE.
Simone Marchi (lead author of the study) stated that impact vapors led to episodic low oxygen levels in the time before the GOE.
“As time passed, collisions became less frequent and too small for us to noticeably alter post-GOE oxygen levels. The Earth was well on its way to becoming the planet it is today.
‘What’s more, we find that the cumulative impactor mass delivered to the early Earth was an important ‘sink’ of oxygen, suggesting that early bombardment could have delayed oxidation of Earth’s atmosphere,’ Marchi added.
The study was published in Nature Geoscience.