Sixty-six million years ago a 10-kilometer-wide space rock fell out of the sky over what is now the Yucatán Peninsula in the Gulf of Mexico. When it hit Earth, it blew a Maryland-sized hole in the crust, igniting global firestorms and killing off some 75 percent of species. For the dinosaurs it drove to extinction, the event was effectively the end of the world. But from the ashes survivors arose—our mammalian ancestors—beginning a vibrant new era in Earth’s history. Today this catastrophic impact is considered a cosmic act of creative destruction, one without which we humans would not exist.
Yet the event’s infamous impactor was nothing compared with the asteroid that struck Earth 3.26 billion years ago, amid what scientists call the Archean eon of our planet’s 4.5-billion-year history. The Archean space rock in that impact, dubbed “S2,” was 50 to 200 times larger—big enough to blast at least 10,000 cubic kilometers of vaporized rock into the skies that then recondensed into molten droplets and rained back to Earth. Unsurprisingly, those circumstances would have been “really disastrous for early life,” says Nadja Drabon, a geologist at Harvard University. But her latest research suggests that—much like the more celebrated dino-killing space-rock impact—this vastly greater and more ancient collision also had an upside, giving Earth’s early biosphere a powerful boost.
“What we found was really stunning,” Drabon says. Working alongside several colleagues, her scrutiny of rock layers in South Africa showed that besides generating world-burning volumes of vaporized rock, the S2 impact triggered massive tsunamis and boiled away the ocean’s uppermost layer. But it also pumped phosphorus and other bioessential elements into the world’s nutrient-starved seas—triggering a bloom of life.
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