How Big of a Threat Are Near-Earth Asteroids?

ABC News
Beyond The Headline

Look up in the sky ... a meteor!

The shooting star lit up 9-1-1 call centers across the Southwest. We all saw the movie "Armageddon," right? So just how worried should we be?

"Your average meteor streak is left by something no larger than half the size of a pea," assured noted astrophysicist Neil deGrasse Tyson.

Fiery rocks from space are a big enough concern the United Nations has just started considering a plan to create an International Asteroid Warning Network.

Astronomers are not too worried about the big stuff, like the meteor that killed off the dinosaurs. That one was the size of Mt. Everest but only happens about once every 100 million years, according to Tyson.

No, what scares them more are meteors like the one that hit Chelyabinsk, Russia, earlier this year. That one was about as big as a house, releasing energy equivalent to a modern-day nuclear warhead!

It could flatten a city.

Scientists thought that was a once-every-100-year event. Now, they're revising their numbers. This week, astronomers report there are many more near Earth asteroids that size or bigger than we realized. Ninety percent of them are not on their radar. In other words, we’d have little to no warning. And no way to defend ourselves.

So next time you see a shooting star, make a wish -- that we'll all be okay.