Asteroids and comets pummeling Earth delayed rise of oxygen

The report states, "Remnants of ancient asteroids revealed Earth was bombarded by massive space rocks more often than previously thought, vastly altering oxygen levels in the planet's early atmosphere. When Earth formed 4.6 billion years ago, it had almost no atmosphere. As the planet cooled, an atmosphere started to form, though it was mainly of carbon dioxide and nitrogen at first, which was inhospitable for life as we know it today. Eventually, Earth experienced a major shift in surface chemistry triggered by the rise of oxygen levels, also known as the Great Oxidation Event (GOE). Between 2.5 and 4 billion years ago, during the Archean eon, asteroids and comets often rained down on Earth. These space rocks (some of which measured more than 6 miles or nearly 10 kilometers wide) greatly impacted the chemistry of the planet's early atmosphere — especially the accumulation of oxygen, according to a new study."

It would seem that abiogenesis during the Precambrian, from all the postulated bombardment needs to be restarted, perhaps again, and again before the *evolutionary tree of life* can take hold here, using the evolution paradigm. How many times did abiogenesis restart during the Precambrian because of the postulated, intense bombardment, now said to take place from about 4 billion to 2.5 billion years ago? The abstract in the paper cited is quite revelaing here.

Delayed and variable late Archaean atmospheric oxidation due to high collision rates on Earth,

"Frequent violent collisions of impactors from space punctuated the geological and atmospheric evolution of early Earth. It is generally accepted that the most massive collisions altered the chemistry of Earth’s earliest atmosphere, but the consequences of Archaean collisions for atmospheric oxidation are little understood. Early Archaean (4.0–3.5 billion years ago (Ga)) impact flux models are tightly constrained by lunar cratering and radiometric data. Further, a record of the late Archaean (3.5–2.5 Ga) impact flux is provided by terrestrial impact spherule layers—formed by collisions with bodies ≥10–20 km in diameter— although this record is probably incomplete and significant uncertainties remain. Here we show, on the basis of an assessment of impactor-related spherule records and modelling of the atmospheric effects of these impacts, that current bombardment models underestimate the number of late Archaean spherule layers. These findings suggest that the late Archaean impactor flux was up to a factor of ten higher than previously thought. We find that the delivered impactor mass was an important sink of oxygen, suggesting that early bombardment could have delayed Earth’s atmosphere oxidation. In addition, late Archaean large impacts (≥10 km) probably caused drastic oscillations of atmospheric oxygen, with an average time between consecutive collisions of about 15 Myr. This pattern is consistent with a known episode of atmospheric oxygen oscillation at ~2.5 Ga that is bracketed by large impacts recorded by Bee Gorge (~2.54 Ga) and Dales Gorge (~2.49 Ga) spherule layers."

How many times did the tiny life forms of the Precambrian, get wiped out here? How many times is needed now to postulate, multiple, repeating abiogenesis events during this period of bombardment?
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