What happened when giant S2 meteor hit Earth 3 billion years ago?— Harvard Gazette
Barberton Greenstone belt of South Africa.
Photo: Nadja Drabon
The problem with that comforting lie is that it isn't borne out by the disturbing truth. Not only is Earth far from perfect for their (human) life over most of its area, being inaccessible and hostile without special human-made technology, but it has been, and probably will be again, subject to almost unimaginable, catastrophic events in its past, such as plate tectonics causing changes in ocean currents which caused climate change so drastic the Earth literally froze over. There have equally been times when the polar icecaps melted flooding coastal areas where many of our modern major cities and ports are located.
And there have been major direct hits by meterites that caused almost instantaneous mass extinctions of a type that humans could hardly survive today and at least one collision with a minor planet early in Earth's history that resulted in an accretion disc that coalesced to form the moon.
Now scientists have found evidence of a massive meteorite, four times the mass of Mount Everest impacting with Earth 3.26 billion years ago. A similar impact today would extinguish just about all life, leaving maybe a few single-celled and primitive organisms to start over again. We are extremely fortunate that the last such meteorite strike was about 66 million years ago, resulting in the extinction of most terrestrial tetrapods like dinosaurs, the pterosaurs and many marine reptiles in the ensuing period of cold and darkness that left just a few survivors amongst which were the early mammals and early birds which inherited the Earth to become todays dominant fauna. Without that meteorite strike we would not exist and another one like it will mean we don't exist anymore.
What would be the consequences of an impact today by a meteorite similar to the one 3*26 billion years ago? A meteorite the size of four Mount Everests hitting Earth today would have catastrophic, planet-wide consequences. Here’s a breakdown of the potential impacts:But that one was small compared to the one 3.26 billion years ago that was some 200 times the size of the one that killed the dinosaurs.
- immediate Blast and Destruction
- Shockwave: The initial blast would create a massive shockwave, vaporizing everything at the impact site and creating an immense crater.
- Earthquakes: Tremors would ripple through the planet, causing earthquakes and landslides thousands of miles from the impact point.
- Tsunamis: If the impact were to occur in an ocean, it would generate colossal tsunamis, devastating coastlines and traveling vast distances.
- Global Firestorm
- Debris Ejection: Rock and molten material would be ejected high into the atmosphere, potentially igniting wildfires over massive areas as the fragments reenter.
- Airburst Effects: Heated particles could start a global chain of fires, devastating ecosystems and covering vast landscapes in flames.
- Massive Climate Disruption
- Dust and Aerosols: Billions of tons of ash, dust, and aerosols would fill the atmosphere, blocking sunlight.
- Global Cooling: With sunlight blocked, Earth’s surface temperature could drop significantly, leading to a prolonged “impact winter.” This could last years, halting photosynthesis and disrupting global agriculture.
- Acid Rain: Volcanic gases and other chemicals released could create acid rain, further harming ecosystems and agriculture.
- Mass Extinctions
- Loss of Biodiversity: Such an impact could drive many species to extinction, especially those unable to adapt to the sudden cooling, darkness, and loss of vegetation.
- Food Chain Collapse: With plant life diminished, herbivores would struggle, causing a domino effect up the food chain, potentially leading to extinctions even among large land and marine predators.
- Human Impact
- Infrastructure and Civilization Collapse: Cities near the impact zone would be obliterated, while global economies and food supplies would be severely affected by disrupted climate and agriculture.
- Health and Survival Challenges: Widespread famine, health crises from polluted air and water, and potential societal breakdown could push humanity to a survival mode on a massive scale.
The end result would be a global event potentially even more severe than the one that contributed to the extinction of the dinosaurs, reshaping Earth’s landscape, climate, and living conditions.
The scientists led by Nadja Drabon, an early Earth geologist and assistant professor in the Department of Earth and Planetary Sciences, Harvard University together with colleagues from Harvard, Stanford University and the University of Zurich, Switzerland, have published their research in Proceedings of the National Academy of sciences (PNAS) and explain it in a news release from Harvard University:
What happened when a meteorite the size of four Mount Everests hit Earth?
Giant impact had silver lining for life, according to new study
Billions of years ago, long before anything resembling life as we know it existed, meteorites frequently pummeled the planet. One such space rock crashed down about 3.26 billion years ago, and even today, it’s revealing secrets about Earth’s past.
Nadja Drabon, an early Earth geologist and assistant professor in the Department of Earth and Planetary Sciences, has questions about what our planet was like during ancient eons rife with meteoritic bombardment, when only single-celled bacteria and archaea reigned — and when it all started to change. When did the first oceans appear? Continents? Plate tectonics? How did all of those violent impacts affect the evolution of life?
Her new study in Proceedings of the National Academy of Sciences attempts to answer some of these questions, in relation to the inauspiciously named “S2” meteoritic impact of more than 3 billion years ago, for which geological evidence is found in the Barberton Greenstone belt of South Africa. Through the painstaking work of collecting and examining rock samples centimeters apart and analyzing the sedimentology, geochemistry, and carbon isotope compositions they leave behind, Drabon’s team paints the most compelling picture to date of what happened the day a meteorite the size of four Mount Everests paid Earth a visit.
Picture yourself standing off the coast of Cape Cod, in a shelf of shallow water. It’s a low-energy environment, without strong currents. Then all of a sudden, you have a giant tsunami sweeping by and ripping up the sea floor.
Najda Drabon, co-lead-author. Department of Earth and Planetary Sciences
Harvard University, Cambridge, MA. USA.
The S2 meteorite, estimated to have been up to 200 times larger than the one that killed the dinosaurs, triggered a tsunami that mixed up the ocean and flushed debris from the land into coastal areas. Heat from the impact caused the topmost layer of the ocean to boil off, while also heating the atmosphere. A thick cloud of dust blanketed everything, shutting down any photosynthetic activity.
Graphical depiction of the S2 impact and its immediate aftereffects.
Before the S2 meteorite is a healthy atmosphere and water system. Immediately following the S2 Meteorite impact is a dust-laden atmosphere and boiling surface. Years to decades later the dust-laden atmosphere and boiling surface has a fallback layer that includes interstitial evaporation. Thousands of years later there is iron-rich sediments and potential mass blooms.
But bacteria are hardy, and following impact, according to the team’s analysis, bacterial life bounced back quickly. With this came sharp spikes in populations of unicellular organisms that feed off the elements phosphorus and iron. Iron was likely stirred up from the deep ocean into shallow waters by the aforementioned tsunami, and phosphorus was delivered to Earth by the meteorite itself and from an increase of weathering and erosion on land.
Drabon’s analysis shows that iron-metabolizing bacteria would thus have flourished in the immediate aftermath of the impact. This shift toward iron-favoring bacteria, however short-lived, is a key puzzle piece depicting early life on Earth. According to Drabon’s study, meteorite impact events — while reputed to kill everything in their wake (including, 66 million years ago, the dinosaurs) — carried a silver lining for life.
We think of impact events as being disastrous for life, but what this study is highlighting is that these impacts would have had benefits to life, especially early on, and these impacts might have actually allowed life to flourish.
Nadja Drabon
These results are drawn from the backbreaking work of geologists like Drabon and her students, hiking into mountain passes that contain the sedimentary evidence of early sprays of rock that embedded themselves into the ground and became preserved over time in the Earth’s crust. Chemical signatures hidden in thin layers of rock help Drabon and her students piece together evidence of tsunamis and other cataclysmic events.
The Barberton Greenstone Belt in South Africa, where Drabon concentrates most of her current work, contains evidence of at least eight impact events including the S2. She and her team plan to study the area further to probe even deeper into Earth and its meteorite-enabled history.
Drabon with students David Madrigal Trejo and Öykü Mete during fieldwork in South Africa.Photo courtesy of Nadja Drabon
SignificanceHopefully, those smug, self-important creationists who like to imagine Earth is perfectly designed for them, won't be around when the next massive ball of rock from the asteroid belt slams into Earth and triggers the next catastrophe which destroys most of life on Earth and presses the metaphorical reset button.
Giant meteorite impacts during Earth’s early history likely had significant effects on early life. We studied the effects on the surface environment and life of a Paleoarchean impactor ~50 to 200× larger than the famous K-Pg impactor. The impact caused a tsunami, partial ocean evaporation, and darkness that likely harmed shallow-water photosynthetic microbes in the short-term, while life in the deeper oceans and hyperthermophiles were less impacted. The impact also released phosphorus into the environment, and the tsunami brought iron-rich deep-water to the surface. As a consequence, there was a temporary bloom of iron-cycling microbes. Giant impacts were not just agents of destruction but also conferred transient benefits on early life.
Abstract
Large meteorite impacts must have strongly affected the habitability of the early Earth. Rocks of the Archean Eon record at least 16 major impact events, involving bolides larger than 10 km in diameter. These impacts probably had severe, albeit temporary, consequences for surface environments. However, their effect on early life is not well understood. Here, we analyze the sedimentology, petrography, and carbon isotope geochemistry of sedimentary rocks across the S2 impact event (37 to 58 km carbonaceous chondrite) forming part of the 3.26 Ga Fig Tree Group, South Africa, to evaluate its environmental effects and biological consequences. The impact initiated 1) a giant tsunami that mixed Fe2+-rich deep waters into the Fe2+-poor shallow waters and washed debris into coastal areas, 2) heating that caused partial evaporation of surface ocean waters and likely a short-term increase in weathering and erosion on land, and 3) injection of P from vaporization of the S2 bolide. Strata immediately above the S2 impact event contain abundant siderites, which are associated with organic matter and exhibit light and variable δ13Ccarb values. This is consistent with microbial iron cycling in the wake of the impact event. Thus, the S2 impact likely had regional, if not global, positive and negative effects on life. The tsunami, atmospheric heating, and darkness would likely have decimated phototrophic microbes in the shallow water column. However, the biosphere likely recovered rapidly, and, in the medium term, the increase in nutrients and iron likely facilitated microbial blooms, especially of iron-cycling microbes.
Numerous studies have shown that large impacts have severe consequences for the surface environment and, thus, can potentially severely affect life (1–5). Most famously, the impact of the 10 km Chicxulub bolide at the K-Pg boundary profoundly disrupted the global environment, including the initiation of a tsunami (6), a sharp, if transient, drop in surface temperatures (7) followed by moderate, longer-term warming (8), short-term darkness (9), and ocean acidification (10). As a result, some 40% of animal genera and as many as 60 to 80% of animal species became extinct (3, 11). Carbon isotopes reveal a disturbance in the ocean’s biological pump due to a severe drop to marine productivity (12, 13). On the other hand, in the longer-term, bolide-induced environmental disruption created new opportunities for survivors, e.g., the mammalian radiation that followed closely on the heels of dinosaur extinction (14). Moreover, and possibly more relevant to an early microbial world, it has been proposed that bolide and target rock vaporization may inject significant volumes of biologically relevant sulfur, phosphorus, and iron into the biosphere (15) for subsequent use by microbial communities.
On the Archean Earth, the impact flux was substantially higher than today; it has been estimated that giant impactors (>10 km in diameter) pummeled the Earth at least every 15 Ma (16). These events likely had severe effects on Earth’s nascent biosphere, but their specific influence is still poorly understood. Modeling predicts that impactors >440 km in diameter could have annihilated much of the biosphere due to evaporation of the entire ocean; impactors ~190 km in diameter would have evaporated the preexisting photic zone (4). Geological evidence supports the partial evaporation (10 s of meters) of oceans by impacts in the form of silica crusts above two Paleoarchean impact layers (17). Mass mortality of non-hyperthermophile microbes in shallow waters was inferred. Early Earth impacts would also have generated large clouds of dust that may have blocked sunlight (9). In addition, essentially all Archean impact deposits show evidence for tsunamis, initiated by oceanic impacts or by slope failure caused by impact-generated seismic activity (17–20). Seismic waves released from the impacts may additionally have caused fracturing of the upper crust (21). On the other hand, impacts may have also conferred benefits on the biosphere; for example, some work has hypothesized that impact-initiated tsunamis mixed nutrient-rich deep waters to the upper water column, making these nutrients available to local ecosystems (5, 19).
The effect of a giant impact on life depends on the size and type of the impactor, the target material, the conditions of the atmosphere and hydrosphere, and the type of life present at the time of impact. While progress has been made on the environmental effects of some Archean impacts, little is known about their effects on early life. To address this issue, we studied two sections across the 3.26 Ga S2 impact event recorded in the lowermost Fig Tree Group, South Africa (informally named “Umbaumba” and “Bruce’s Hill”; SI Appendix, Fig. S1). The S2 impactor had an estimated bolide diameter of 37 to 58 km (22), by mass ~50 to 200 times larger than the K-Pg bolide. We analyzed the sedimentology, petrography, trace element geochemistry, total organic carbon (TOC) content, and carbon isotope geochemistry of carbonaceous matter and carbonate, with the goal of evaluating the effects of the S2 impact on early surface environments and life.Fig. 1
Rock and thin section images of the Bruce’s Hill and Umbaumba sections. (A–C) Outcrop photos of the Umbaumba section. (A) Overview of the Umbaumba section showing, from base to top, BWBC, S2, fallback layer, and BWBC. (B) S2 spherule bed. (C) Lower part of the fallback layer showing fine laminations. This black chert is composed of silicified carbonaceous matter, siliciclastic debris, and impact-generated dust settling out of the atmosphere. (D and E) Outcrop photos of the Bruce’s Hill section. (D) BWBC below S2. (E) Alternating siliciclastic and siderite-rich chert beds. (F–G) Representative thin section images of carbonaceous matter. (F) Laminated carbonaceous chert below S2 in the Umbaumba section (SI Appendix, Fig. S4). Red arrows indicate fractures filled by chert. (G) Clots of carbonaceous matter and other siliciclastic debris from the fallback later in the Umbaumba section.Drabon, Nadja; Knoll, Andrew H.; Lowe, Donald R.; Bernasconi, Stefano M.; Brenner, Alec R.; Mucciarone, David A.
Effect of a giant meteorite impact on Paleoarchean surface environments and life Proceedings of the National Academy of Sciences 121(44), e2408721121. DOI: 10.1073/pnas.2408721121
Copyright: © 2024 The authors.
Published by National Academy of Sciences. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
Perhaps those same creationists can take comfort from the fact that all these catastrophes stuck Earth in the 99.9975% of Earth's history that hapened before they think it was made by magic out of nothing.
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