A team led by the Southwest Research Institute (SwRI) has updated its Earth asteroid bombing model with the latest geological evidence of ancient, large-scale collisions. These models were used to understand how the impacts might have affected oxygen levels in Earth’s atmosphere in the archaic eon between 2.5 to 4 billion years ago.
This group analyzed a type of special particles in the Earth’s crust, concluding that the frequent impact of asteroids had direct consequences on our planet’s oxygen level.
Asteroid bombing to Earth may have smothered life
When large asteroids or comets hit the early Earth, the energy released melted and vaporized rocky materials in the earth's crust. The small droplets of molten rock in the impact column will have condensed, solidified and fell back to Earth.
This action created round particles the size of sand distributed globally. Known as impact beads, these glassy particles populated several thin, discrete layers of the earth's crust, ranging in age from 2.4 to 3.5 billion years.
According to the team that led this investigation, these layers of Archean beads are markers of ancient collisions.
In recent years, a series of new bead layers have been identified in drill cores and outcrops, increasing the total number of impact events known during Earth's early days.
Explained Dr. Nadja Drabon, professor at Harvard University and co-author of the study.
Current bombing models underestimate the number of bead layers in the late Archean, suggesting that the impact flux at that time was up to 10 times greater than previously thought.
Furthermore, we found that the cumulative mass of the impact inflicted on the early Earth was an important 'reservoir' of oxygen, suggesting that the initial bombardment might have delayed the oxidation of the Earth's atmosphere.
He told Dra. Simone Marchi do SwRI.
Impacts led to an oxygen shortage
The abundance of oxygen in the Earth's atmosphere is due to a balance between production and removal processes. These new discoveries correspond to the geological record, which shows that oxygen levels in the atmosphere varied but remained relatively low in the early archaic aeon.
Impacts produced by bodies larger than 10 km in diameter may have contributed to their scarcity, as the limited oxygen present in the early Earth's atmosphere would have been chemically consumed by the impact vapors, further reducing their abundance in the atmosphere.
Late archaic bombardment by objects over 10 meters in diameter would have produced enough reactive gases to consume completely low levels of atmospheric oxygen.
This pattern was consistent with evidence of so-called 'puffs' of oxygen, relatively steep but transient increases in atmospheric oxygen that occurred about 2.5 billion years ago. We think the blows were interrupted by impacts that removed oxygen from the atmosphere. This is consistent with the large impacts recorded by spherical layers at Bee Gorge and Dales Gorge in Australia.
said Dr. Laura Schaefer, professor at Stanford University and co-author of the article.
According to what the SwRI results indicate, the Earth was subjected to a substantial number of major impacts during the late Archean era. About 2.4 billion years ago, during the end of this bombardment, Earth underwent a major change in surface chemistry triggered by increased atmospheric oxygen, dubbed the Large Oxidation Event (GOE), which is attributed to changes in the balance between oxygen production and sinking.
Among the proposed scenarios are a presumed increase in oxygen production and a decrease in gases capable of removing oxygen, either from volcanic sources or through its gradual loss to space.
Then, over time, collisions become progressively less frequent and too small to be able to significantly alter post-GOE oxygen levels. Earth was on its course to become the current planet.
Read too:
-
