Could an asteroid destroy Earth?

Could an asteroid destroy Earth?

When large asteroids hit the Earth, they trigger mass extinctions and climate chaos. But could an asteroid destroy the planet entirely?

Science & Tech

After dominating the Earth for more than 160 million years, the dinosaurs finally met their doom thanks to a visitor from space. Around 66 million years ago, an asteroid measuring at least 6 miles (10 kilometers) across dealt the dinosaurs' world a devastating blow, triggering earthquakes, tsunamis, volcanic eruptions and climate catastrophes that soon rendered 75% of all living creatures extinct.

But, through all this, Earth itself remained.

Does this mean our planet is immune to an asteroid Armageddon? If the dreaded dino-killing asteroid wasn't enough to end the world, then what would it take? Could a space rock actually destroy the entire Earth — and how big would it have to be?

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The short answer is: It would probably take a rock as big as a planet to destroy our planet. But it would take far, far less to obliterate life on Earth — or most of it, anyway.

"An object bigger than Mars hit Earth early in its history and made the moon, without destroying the Earth," Brian Toon, a professor of atmospheric and oceanic sciences at the University of Colorado Boulder who has studied asteroid impacts, told Live Science in an email.

Toon is referring to the giant impact hypothesis — a scientific theory that suggests a Mars-size planet named Theia collided with Earth 4.5 billion years ago, launching a salvo of rocky debris into space that eventually coalesced into our moon. (Mars measures about 4,200 miles, or 6,700 km wide — more than 500 times the width of the dinosaur-destroying asteroid.)

Rather than obliterating our planet, scientists theorize that part of Theia's core and mantle fused with our own, remaining underfoot in the coming eons when the first life evolved. Experts disagree as to whether this ancient collision was head-on or just a glancing blow, but there's no doubt that had anything been alive on Earth at the time, Theia would have wiped it out. (Scientists think life could have appeared as early as 4.4 billion years ago, a few million years after the Theia impact.)

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