In the past, chaos was prevalent on Earth. Enormous asteroids and remnants of ancient celestial bodies frequently impacted planets within the turbulent solar system. Scientists have discovered evidence indicating that a colossal object struck the Earth, approximately 3.26 billion years ago, at a size 50 to 200 times greater than the asteroid responsible for the extinction of the dinosaurs. This impact is believed to have boiled the oceans, plunged the planet into darkness lasting years, and generated tsunamis thousands of meters deep that devastated coastal seafloors. Despite such catastrophic events, recent studies reveal that primitive life managed to thrive during this period.
Earth and planetary scientist Nadja Drabon, who led this study from Harvard University, stated that impact events are often perceived as catastrophic for life. However, the study suggests that these impacts may have facilitated the flourishing of life, particularly in its early stages. The research focused on the “S2” meteorite impact event and was recently published in the Proceedings of the National Academy of Sciences.
This particular impact is suspected of creating a massive crater approximately 297 miles (487 kilometers) wide, leaving behind rock formations that can still be observed in South Africa today. These formations bear distinctive characteristics from the ancient collision. Drabon and her research team meticulously analyzed layers of these ancient rocks, gathering over 200 samples from both below and above the fallback layer of debris.
The examination of these post-impact layers revealed significant changes in their formation and composition, particularly an increase in iron and iron-rich minerals known as siderites. These minerals typically form in environments where microbes utilize iron as an energy source, which suggests that microbial life likely thrived in these areas, even as many sunlight-dependent primitive organisms perished.
The authors of the study also noted that while the impact, accompanied by tsunamis, atmospheric heating, and darkness, likely decimated phototrophic microbes in shallow waters, the biosphere rapidly recovered. In the medium term, the increase in nutrients and iron likely encouraged microbial blooms, especially among iron-cycling microbes. The study’s accompanying graphic illustrates how the immense tsunamis distributed iron throughout the water column, benefiting iron-ingesting microbes.
The Barberton Greenstone Belt in South Africa serves as a crucial site for Earth scientists investigating the planet’s distant, often tumultuous history. The asteroid that impacted Earth approximately 3.26 billion years ago was many times the size of Mount Everest.
Today, large-scale impacts from celestial objects have become rare on Earth. However, both tiny and large asteroids and comets still pose risks. For example, a surprise 56-foot (17-meter) rock exploded over Russia in 2013, demonstrating that even smaller space rocks can be perilous.
On a daily basis, about 100 tons of dust and sand-sized particles fall through Earth’s atmosphere, eventually burning up. Annually, an asteroid roughly the size of an automobile enters the atmosphere and explodes, as explained by NASA. Impacts from objects around 460 feet (140 meters) wide occur every 10,000 to 20,000 years. A “dinosaur-killing” event, involving a rock potentially half a mile wide, is predicted to occur on timescales of approximately 100 million years.
