San Antonio TX (SPX) Oct 25, 2021 A team led by Southwest Research Institute has updated its...
A team led by Southwest Research Institute has updated its asteroid bombardment model of the Earth with the latest geologic evidence of ancient, large collisions.
"In recent years, a number of new spherule layers have been identified in drill cores and outcrops, increasing the total number of known impact events during the early Earth," said Dr. Nadja Drabon, a professor at Harvard University and a co-author of the paper.
"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."
These new findings correspond to the geological record, which shows that oxygen levels in the atmosphere varied but stayed relatively low in the early Archean eon.
Impacts by bodies larger than six miles in diameter may have contributed to its scarcity, as limited oxygen present in the atmosphere of early Earth would have been chemically consumed by impact vapors, further reducing its abundance in the atmosphere.
"Late Archean bombardment by objects over six miles in diameter would have produced enough reactive gases to completely consume low levels of atmospheric oxygen," said Dr. Laura Schaefer, a professor at Stanford University and a co-author of the paper.
SwRI's results indicate that the Earth was subject to substantial numbers of large impacts throughout the late Archean era.
Around 2.4 billion years ago, during the tail end of this bombardment, the Earth went through a major shift in surface chemistry triggered by the rise of atmospheric oxygen, dubbed the Great Oxidation Event, which is attributed to changes in the oxygen production-sink balance.
"As time went on, collisions become progressively less frequent and too small to be able to significantly alter post-GOE oxygen levels. The Earth was on its course to become the current planet."
In our own solar system, the Earth and moon are thought to be products of this type of giant impact.