Scientists provide an intriguing insight into the events that took place when the S2 meteorite struck Earth 3.26 billion years ago.
Long before life as we recognize it emerged, the Earth was regularly bombarded by meteorites. Around 3.26 billion years ago, one such rock descended upon our planet, continuing to reveal mysteries about its history up to the present day.
Nadja Drabon, a geologist focused on early Earth and an assistant professor in the Department of Earth and Planetary Sciences, has a deep interest in understanding our planet’s conditions during ancient times marked by meteor impacts, a period dominated by single-celled bacteria and archaea, paving the way for future evolution. Key questions remain: When did our oceans first form? What about the emergence of continents and plate tectonics? How did these explosive events influence the development of life?
Recent research published in Proceedings of the National Academy of Sciences addresses some of these inquiries, centering on the modestly named “S2” impact from over 3 billion years ago, with geological traces found in South Africa’s Barberton Greenstone Belt. Drabon’s team undertook meticulous work, gathering and analyzing rock samples just a few centimeters apart, reviewing the sedimentology, geochemistry, and carbon isotope profiles they exhibited, leading to a clearer understanding of the day that a meteorite, comparable in size to four Mount Everests, struck Earth.
“Imagine standing off the coast of Cape Cod, in a gentle shelf of shallow water. It’s a calm environment without strong currents. Suddenly, a massive tsunami engulfs the area, upheaving the sea floor,” Drabon explained.
The S2 meteorite, believed to have been up to 200 times larger than the asteroid ultimately responsible for the extinction of the dinosaurs, instigated a tsunami that churned the ocean and transported land debris into coastal waters. The impact’s heat vaporized the surface layer of the ocean, while simultaneously warming the atmosphere. A dense cloud of dust spread across the area, halting any photosynthetic processes occurring at that time.
Nevertheless, bacteria proved to be resilient, and according to the team’s findings, they rapidly rebounded post-impact. This recovery resulted in significant increases in populations of unicellular organisms that thrive on phosphorus and iron. The tsunami likely disturbed iron from the deep ocean into shallower waters, while the meteorite brought phosphorus and contributed to enhanced weathering and erosion on land.
Drabon’s research indicates that iron-metabolizing bacteria flourished immediately following the impact. Although this shift towards iron-utilizing bacteria was brief, it is a crucial aspect of understanding early life on Earth. Drabon’s study suggests that while meteorite impacts are known to wipe out life (as seen 66 million years ago with the dinosaurs), they also held surprising benefits for the continuation of life.
“We typically perceive impact events as catastrophic for life,” Drabon remarked. “Yet, this research underscores that these impacts may have actually aided early life, providing opportunities for it to thrive.”
The findings result from the diligent efforts of geologists like Drabon and her students, who trek through mountain terrains to uncover sedimentary records of ancient rock sprays that became embedded and preserved in the Earth’s crust. Chemical signatures found within thin rock layers assist Drabon and her team in reconstructing evidence of tsunamis and other catastrophic occurrences.
The Barberton Greenstone Belt in South Africa, where Drabon focuses her current research, holds records of at least eight separate impact events, including the S2. She and her team aim to explore this region further, delving deeper into Earth’s meteorite-influenced past.
