What could have caused such an extreme event? During the Ordovician period, the continents were one jumbled mass called Gondwana. The planet saw a sudden drop in oxygen levels that lasted for several million years. However, one of Earth’s great die-offs, an event 450 million years ago called the Late Ordovician mass extinction, likely happened because the inverse took place. An eruption of cyanobacteria, sometimes called blue-green algae, filled our atmosphere with oxygen, creating a world where multicellular life-forms could take hold, and where creatures like humans could ultimately breathe. Nearly 2.5 billion years ago, a period called the Great Oxidation Event gave us the breathable atmosphere we all now depend on. But these days, collisions of such large objects are extremely unlikely.įor a more likely glimpse of an Earth-altering cataclysm, we need to look to the distant past. There is evidence that infant Earth was struck by a large planetoid called Theia. And only asteroids like Pallas and Vesta - the solar system’s largest - are big enough to do that. Killing all life on Earth would require an impact that literally boils away the oceans. There’s even evidence that some people may have been killed by small meteorite impacts within the past few thousand years.īut what are the chances that our planet will ever be struck by an asteroid massive enough to wipe out all life on Earth? Simulations published in Nature back in 2017 suggest it would take a truly gigantic space rock to accomplish such a feat. However, smaller asteroid impacts do happen all the time. Based on the geological record of cosmic impacts, Earth gets hit by a large asteroid roughly every 100 million years, according to NASA.
Fortunately, that’s unlikely to happen anytime soon. A future asteroid could just as easily take out every person on Earth. Humans, however, won’t always be on the winning side of such random events. And while our ancestors hadn’t yet evolved, the impact was perhaps the single most important event in human history. Without that asteroid strike, dinosaurs might have continued to rule the Earth, leaving us mammals still cowering in the shadows. When a city-sized asteroid struck the Gulf of Mexico 66 million years ago, it was game over for the dinosaurs, as well as most other species on Earth at the time.
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