A series of asteroids the size of the city bombed the early Earth between 2.5-3.5 billion years ago – and struck with a frequency of one strike every 15 million years.
This means that the attack may have been ten times more intense than previously estimated, experts from the Southwest Research Institute have reported.
These impactors, the team explained, would have been significantly larger than the asteroid believed to have killed the dinosaurs, which were only seven miles wide.
While craters formed by these ancient influences have long been weathered or destroyed, traces of them may still be in the form of glassy particles called spheres.
These spheres were formed as a result of the shocks that threw melted particles and vapors into the atmosphere, where they cooled and fell back to earth.
Their distribution can also reveal information about the size of a striking body ̵
A series of asteroids in the city (as illustrated) bombed the early Earth between 2.5-3.5 billion years ago – and struck with a frequency of one stroke every 15 million years
A series of asteroids the size of the city bombed the early Earth between 2.5-3.5 billion years ago – and struck with a frequency of one strike every 15 million years. The image: an artist’s impression of the archaic surface of the earth, the period when simple life first emerged
Archean is the name of the second geological eon in Earth’s history that ran from 4-2.5 billion years ago.
Into this time period, the planet was cooled enough to allow the first continents to form and primitive life to emerge.
The latter took the form of mats of microbes – which leaves characteristic stratified residues called ‘stromatolites’ in the fossil record.
It is believed that the archaic atmosphere lacked free oxygen, but – due to a relative abundance of greenhouse gases – maintained a surface temperature similar to that of today, despite the sun being only 70-75 percent of its current brightness.
Unlike later geological eons and period, Archean is defined not by a specific boundary layer in the Earth’s stratigraphy, but by absolute dating.
‘We have developed a new power flux model and compared it to a statistical analysis of old spherical layer data,’ said paper author and physicist Simone Marchi of the Southwest Research Institute in Colorado.
‘We found that current models of the Earth’s early bombardment seriously underestimate the number of known impacts, as recorded by spherical layers. The true current of effect could have been up to a factor of 10 times higher than previously assumed. ‘
This, explained dr. Marchi, means that in the period between 3.5-2.5 billion years ago ‘we were probably hit by a Chicxulub effect on average every 15 million years. Something a spectacle! ‘
‘As we deepen our understanding of the early earth, we find that cosmic collisions are like the proverbial elephant in space,’ continued Dr. Marchi.
‘They are often neglected as we lack a detailed knowledge of their number and size, but it is likely that these energetic events fundamentally altered the earth’s surface and atmospheric evolution.’
‘An example we look at is e.g. To try to understand whether these influences may have influenced the evolution of atmospheric oxygen. We find that oxygen levels would have fluctuated drastically during the period of intense influences. ‘
‘Given the importance of oxygen for the evolution of the earth and indeed for the evolution of life, its possible connection with collisions is intriguing and deserves further study. This is the next phase of our work. ‘
‘These large impacts would certainly have caused some disturbance,’ said geologist Rosalie Tostevin of the University of Cape Town in South Africa, who was not involved in this study. The image: the aptly named Meteor Crater in Arizona – the result of an impact body only 164 feet in diameter, far smaller than the bodies that bombarded the Earth during the Archaic
‘These large impacts would certainly have caused some disturbance,’ said geologist Rosalie Tostevin of the University of Cape Town in South Africa, who was not involved in this study.
‘Unfortunately, few rocks survive so far back in time, so direct evidence of impacts and their ecological consequences is uneven,’ she added.
‘The model presented by Dr. Marchi helps us get a better sense of the number and magnitude of collisions on early Earth. ‘
‘Some chemical markers suggest that there was an “odor” of oxygen in the early atmosphere before a permanent rise about 2.5 billion years ago.’
‘But there is considerable debate about the meaning of these “whiffs,” or whether they took place at all.’
‘We tend to focus on the Earth’s interior and the evolution of life as a control over the Earth’s oxygen balance,’ noted Dr. Tostevin.
‘But bombardments with rocks from space provide an exciting alternative.’
The full findings of the study were presented at the Goldschmidt Conference in 2021, which will be held practically this year from 4 to 9 July.
Explained: The difference between an asteroid, meteorite and other space rocks
One asteroid is a large rock rock left from collisions or the early solar system. Most are located between Mars and Jupiter in the main belt.
ONE comet is a rock covered with ice, methane and other compounds. Their orbits lead them much further out of the solar system.
ONE meteor is what astronomers call a flash of light in the atmosphere when waste burns up.
This waste in itself is known as one meteoroid. Most are so small that they evaporate into the atmosphere.
If any of this meteoroid reaches Earth, it’s called one meteorite.
Meteors, meteoroids and meteorites usually originate from asteroids and comets.
For example, if the Earth passes through the tail of a comet, much of the debris burns up into the atmosphere and forms a meteor shower.