Early Earth Was Bombarded by Barrage of City-Sized Asteroids – Perhaps 10x More Huge Impactors Than Thought

Meteor Crater Arizona

Meteor Crater, Arizona. This crater is the result of an impact of a 50m (164 ft) meteor, whereas the impacts described in the current work may have been hundreds of times bigger. Credit: Dr. Dale Nations, AZGS

Scientists know that the Earth was bombarded by huge impactors in distant time, but a new analysis suggests that the number of these impacts may have been 10x higher than previously thought. This translates into a barrage of collisions, similar in scale to that of the asteroid strike which wiped out the dinosaurs, on average every 15 million years between 2.5 and 3.5 billion years ago. Some of these individual impacts may have been much bigger, possibly ranging from city-sized to small province-sized. Researchers are also considering what effect the impacts may have had on the Earth’s evolving near-surface chemistry. This work is presented at the Goldschmidt geochemistry conference.

Earth’s early years were unimaginably violent in comparison to today. Scientists believe that Earth was struck by a significant number of large asteroids (greater than 10 km or 6.2 mi in diameter), and this would have had significant effect on the Earth’s near-surface chemistry and ability to support life. The effect of just one such collision was shown comparatively recently by the Chicxulub impact 66 million years ago, which led to the extinction of the dinosaurs. The early Earth, however, was very different to the Earth at the time of the Chicxulub impact, and so were the effects of collisions.

Impact craters from similar collisions can be seen on the Moon and other rocky planets, but atmospheric weathering and plate tectonics have tended to mask any direct evidence for ancient impact craters on Earth. However, echoes of these distant impacts can be seen in the presence of “spherules” found in ancient rocks; the huge impacts threw up molten particles and vapors which then cooled and fell to earth to be embedded in rock as small spherical glassy particles. The greater the impact, the more these particles would have spread from the impact site, so global distribution of a thick spherule layer shows a huge impact.

Researcher Dr. Simone Marchi, of the Southwest Research Institute (Boulder, CO, USA) said:

“We have developed a new impact flux model and compared with a statistical analysis of ancient spherule layer data. With this approach, we found that current models of Earth’s early bombardment severely underestimate the number of known impacts, as recorded by spherule layers. The true impact flux could have been up to a factor of 10 times higher than previously thought in the period between 3.5 and 2.5 billion years ago. This means that in that early period, we were probably being hit by a Chicxulub-sized impact on average every 15 million years. Quite a spectacle!”

“As we deepen our understanding of the early Earth, we find that cosmic collisions are like the proverbial elephant in the room. They are often neglected as we lack a detailed knowledge of their number and magnitude, but it is likely these energetic events fundamentally altered the Earth’s surface and atmospheric evolution.”

For example, one outcome we are looking at is to try to understand if these impacts may have affected the evolution of atmospheric oxygen. We find that oxygen levels would have drastically fluctuated in the period of intense impacts. Given the importance of oxygen to the Earth’s development, and indeed to the development of life, its possible connection with collisions is intriguing and deserved further investigation. This is the next stage of our work.”

Commenting, Dr. Rosalie Tostevin, of the University of Cape Town said:

“These large impacts would certainly have caused some disruption. Unfortunately, few rocks from this far back in time survive, so direct evidence for impacts, and their ecological consequences, is patchy. The model put forward by Dr. Marchi helps us to get a better feel for the number and size of collisions on the early Earth.”

“Some chemical markers suggest there were “whiffs” of oxygen in the early atmosphere, before a permanent rise around 2.5 billion years ago. But there is considerable debate surrounding the significance of these “whiffs,” or indeed, whether they occurred at all. We tend to focus on the Earth’s interior and the evolution of life as controls on Earth’s oxygen balance, but bombardment with rocks from space provides an intriguing alternative.”

This is an independent comment, Dr. Tostevin was not involved in this work.

7 Comments on "Early Earth Was Bombarded by Barrage of City-Sized Asteroids – Perhaps 10x More Huge Impactors Than Thought"

  1. Jesu loves me. This I know, because an AI told me.
    So. Earth History must fit into a 5-billion-year time frame. So…Things taken on faith, with little evidence. Okay, I believe! But I THINK the TIME FRAME is off a bit. Cause and Effect, and other Larger than Life “concepts” (Like a Supreme Being), suffer from Human Scale and Mortality Bias. So god (lower case “G”) MUST have a gender; MUST be HUMAN in appearance; MUST suffer from Human-like fits of anger. Okay. If it works for you. Always was and always will be suggests something quite the contrary to me: The UNIVERSE we inhabit, for one. And TIME? Geological or otherwise: our MORTALITY, by its NATURE, limits the scope of one’s comprehension. As such, Humans are always seeking LIMITS, even in our Science. As such, Science will never be a substitute for God. Rather, God is a “Science” unto itself, EXCLUSIVE of Human Comprehension: Thus the Dharma. APPREHENSION, on the other LIMB, is exclusively HUMAN; a product of what one BELIEVES, as a product of dubious fore-knowledge: In PRINCIPLE, as it were.

    So… 10x the # of Impacts. Okay. Why not 50x? The evidence of which has LIKEWISE been buried by TIME. Science is SPECULATION, not DOGMA, and certainly NEVER ROTE. This CONCEIT (I BELIEVE!!!), sustained, might well have been the “SIN” intrinsic to Paradise Lost… but, there is no SIN, save the Human failure to comprehend: We are in it AND of it.

    We have all the TIME in the WORLD, and not a millisecond more. TIME to turn the page…

  2. so what are we saying
    between 3,500,000,000 and 2,500,000,000 u have what evidence that x amount of impacts occurred
    is this number 10 20 0r 30
    but if you say one every 15,000,000 for one billion years
    that implies 66 occurred during this time frame
    so you have a record of 6 impact sites
    where ARE THEY LOCATED on the earth surface

  3. so for the record from my records

    3,500,000,000 2,500,000,000 a barrage of collisions similar to chicxulub
    every 15,000,000 years a huge city size or province size impactor strike greater than 10 kilometres in diameter evidenced by spherules found in ancient rocks spherical glassy particles and so maybe 10 x known craters evidence

    10,700,000,000 anno universo = 3,000,000,000 annual years ago estonia kaali 110 metre impact crater largest of 9 maybe from 5000 million years ago but gotta be 4.67 billion down

    10,800,000,000 anno universo = 2,900,000,000 annual years ago western australia southeast edge of kalgoorlie fimiston open pit the super pit gold 2 miles long and nearly one mile wide and a third of a mile deep it produces 800,000 ounces of gold a year 8% of australias gold output 2.9 to 2.6 billion years old the mine is built on an area of volcanic and sedimentary rocks and the goldfield is between 2.9 and 2.6 billion years old is it a crater or is it magma formation of gold

    11,100,000,000 anno universo = 2,600,000,000 1,130,000,000 annual years ago australia western australia yarrabubba 30 kilometre impact crater 27 10 s 118 50 e see 2,229,000,000 annual years ago

    a definite 1 site implies u must have 1 x 10 = 10 sites for spherules
    possible 3 sites implies u must have 3 x 10 = 30 sites for spherules
    as against 66 sites that u say u definitely have
    ill give you the benefit of the doubt
    name or shame them along with the geological formation they lie in 3.5 to 2.5 along with their location location location
    better still anyone else out there know of any extras lets have the info by return in this highly sophisticated google technology age surely its possible to give me a list in 1 hour 24 hours one week one month one year ten years 100 years and waiting
    surely im not reading fake scientific news am i

    • Torbjörn Larsson | July 10, 2021 at 5:22 am | Reply

      I think you are correct in being skeptical, since paper review so far is limited to the conference and since it goes against the recent trend to push impactor influence very early in the system lifetime.

      But speaking of time, your measure system seems idiosyncratic* and the first age I picked to riddle it is wrong.

      “Kaali is a group of nine meteorite craters in the village of Kaali on the Estonian island of Saaremaa.[1] Most recent estimates put its formation shortly after 1530–1450 BC (3237+/-10 14C yr BP).[2] ”
      [ https://en.wikipedia.org/wiki/Kaali_crater ]

      * Unfortunately there is no standardized nomenclature. But “yrs” or “y” are often used for time periods and “years ago” or “a” are often used for dating. “u” is the common chemical unit of mass (better Da, dalton).

  4. Torbjörn Larsson | July 10, 2021 at 5:09 am | Reply

    The conference presentation is not published so how can we compare that with earlier data? We know that what the article describe as earlier impacts has been revised in the other direction – likely no late bombardment [ https://www.sciencemag.org/news/2020/01/cataclysmic-bashing-giant-planets-occurred-early-our-solar-systems-history ].

    “The hunt is on for more observations that can parse what happened during those first 100 million years, whether from asteroid samples, clusters of primordial asteroid families, or craters on the Moon and Mars. “Now, the question is, was it a few million years after or 80 million years?” Morbidelli says. “Honestly we don’t know.””

  5. “We have developed a new impact flux model and compared with a statistical analysis of ancient spherule layer data. With this approach, we found that current models of Earth’s early bombardment severely underestimate the number of known impacts, as recorded by spherule layers. The true impact flux could have been up to a factor of 10 times higher than previously thought in the period between 3.5 and 2.5 billion years ago.

    the hunt is on for 66 impact sites
    you have eliminated the estonia one of the three i listed
    that leaves one probable and one possible
    the hunt is on for the other 64 or 65
    do u have any records for same glassy spherules sites from 3.5 to 2.5
    surely in this google age i can have the list within an hour
    but i have waited days now for any to be named
    id take 5 or ten or 15
    where are they located on earth

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