How an Ancient Meteorite Kickstarted Life on Earth: Nature's Fertilizer Bomb
The dinosaurs and many other life forms were killed when a space rock collided with Earth 66 million years ago near the end of the Cretaceous Period. However, it was by no means the biggest meteorite to hit Earth.
3.26 billion years ago, one up to 200 times larger landed, causing much more extensive global devastation. But according to recent research, that catastrophe might have actually aided in the early evolution of life by acting as "a giant fertilizer bomb" that gave the bacteria and other single-celled organisms known as archaea, which ruled at the time, access to the essential nutrients iron and phosphorous.
Using evidence from ancient rocks in the Barberton Greenstone Belt, an area in northeastern South Africa, researchers evaluated the impact of this meteorite. They discovered many indications that life recovered gracefully, primarily from the geochemical signature of preserved organic matter but also from fossils of marine bacterial mats.
According to Harvard University geologist Nadja Drabon, main author of the study that was published on Monday in the journal Proceedings of the National Academy of Sciences, "life not only recovered swiftly once conditions returned to normal within a few years to decades, but it really thrived." This happened during the Paleoarchean Era, when meteorite impacts were more common and larger, and Earth was a very different planet.
Earth was essentially a water world at this epoch, with few volcanoes and continental rocks emerging. According to Andrew Knoll, a Harvard geologist and co-author of the paper, "there was practically no oxygen gas in the atmosphere and oceans, and no cells with nuclei."
Rich in carbon and phosphorus, the meteorite was a kind known as a carbonaceous chondrite. With a diameter of roughly 23–36 miles (37–58 kilometers), it was roughly 50–200 times the mass of the asteroid that exterminated the dinosaurs, excluding their bird offspring, according to Drabon.
The impact's repercussions would have been swift and intense. The impactor struck with such force that it vaporized the rock or sediment it struck. In a matter of hours, the dust and cloud of rock vapor that were expelled from the crater would have circled the world and darkened the sky, according to Drabon.
The impact most likely happened in the water, causing a tsunami to break up the sea floor and flood coasts as it swept around the world. Finally, a significant portion of the impact energy would be converted to heat, causing the atmosphere to warm to the point where the seas' top layer began to boil, Drabon continued.
The dust would have likely settled and the atmosphere would have cooled sufficiently for the water vapor to return to the ocean over a period of years to decades, Drabon added. Microbes in shallow waters and those that rely on sunshine would have been completely destroyed. However, phosphorous, a nutrient essential for the molecules at the heart of storing and transmitting genetic information, would have been abundantly supplied by the meteorite.
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