How Big Does An Asteroid Have To Be To Destroy All Life?

Experts tell us what the impacts are based on size.

Video of How Big Does An Asteroid Have To Be To Destroy All Life?

Karin Heineman, Executive Producer

(Inside Science TV) -- Ever wonder how big an asteroid would have to be to wipe out life on the planet?

Turns out about 60 miles wide.

Scientists have been looking at potential asteroid impacts for years.

University of Colorado Boulder, geoscientist Brian Toon figures one rock about a half a mile wide can do a lot of damage and cause widespread Earthquakes, releasing the energy equal to 100 billion tons of TNT.

But even that wouldn't be completely catastrophic. Scientists think the object that may have hastened the death of the dinosaurs was about seven to eight miles wide, sending a dust plume so big it engulfed the planet, igniting fires and basically broiling the dinosaurs.

A similar collision today would likely kill billions of people … most of the animals and all the vegetation. It's possible a few people could survive but they would have a hard time finding food.

Richard Binzel, a professor of planetary sciences at MIT says even though it's possible this could happen someday, there are no asteroids big enough in any orbit that can completely destroy Earth.

What would happen if a smaller asteroid, one the size of a house, crashed into Earth at 30,000 miles per hour? Experts say it would flatten concrete buildings up to a half mile from where it hit.

What if the asteroid was the size of a 20-story building? It would flatten all the buildings within five miles.

The next near Earth asteroid will make its closest approach on October 26th, 2028. The asteroid's path is predicted to pass beyond the Moon's distance from the Earth. In fact, it will still be about two and half times farther away from the Earth than the Moon. It measures a mile-wide and is traveling at a speed of 30-thousand miles per hour. If it did strike New York City, the force would flatten everything from D.C. to Boston.

But not to worry – NASA says it will have zero impact on Earth.

To help keep us all safe from any possible future asteroids – NASA is developing an asteroid re-direct mission. It's a first-of-its-kind mission for a spacecraft to land on a large asteroid, grab a huge boulder from its surface for further study and then re-direct the asteroid into a stable orbit around the Moon. This mission is set to launch by 2020. Get Inside The Science:

What Is NASA's Asteroid Redirect Mission?

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