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See where 26 asteroids smacked Earth with A-bomb force

The B612 Foundation highlights the fact that asteroids come a-knockin' 3 to 10 times more frequently than previously thought. But don't freak out; most explode too high up to cause damage on the ground.

This fireball seen over California and Nevada in 2012 caused no damage, but impacted the atmosphere with the force of an atomic bomb. NASA/Lisa Warren

Happy Earth Day, folks! Now let's take a look at how close Earth -- or at least one of its major cities -- is to getting wiped out with next to no notice. According to the B612 Foundation, the threat of destructive asteroid impacts is about 3 to 10 times higher than previously thought.

The B612 Foundation was started by former astronauts Ed Lu and Rusty Schweickart, and one of the organization's primary goals is to launch a space telescope dubbed " Sentinel." It's main mission would be to keep track of potentially threatening asteroids and near-Earth objects, in order to provide a warning and response time.

As part of a dramatic pitch for the mission, B612 held a press conference and released the below visualization Tuesday in honor of Earth Day, showing over two dozen locations where asteroids have impacted Earth, exploding with the force of at least one atomic bomb. The visualization was created using data from the International Monitoring System of the Comprehensive Nuclear-Test-Ban-Treaty Organization, which can detect such powerful explosions anywhere in the world.

The B612 Foundation, of course, has a stake in highlighting asteroid frequency. Still, those who keep track of such things might be interested to hear that "our previous estimates of the impact odds for small asteroids (such as city killers) were low by about a factor of 3 to 10. This new data suggests that Earth is hit in a random location by a multi-megaton asteroid impact (large enough to destroy a major city) about every hundred years," according to a companion FAQ for the video.

Another fact that's likely to amp up your freak-out meter is that almost none of these asteroid strikes were detected before impact, and those that were came with no more than a few hours warning.

But let's take this down a big giant notch. Before you start asking your parents and grandparents for the keys to the abandoned family fallout shelter, it's important to note that most of the asteroid impacts in the video below resulted in an explosion high enough in the atmosphere that no damage was reported on the ground.

The notable exception is the 2013 metor that shattered windows all over a Russian city before eventually landing in a remote frozen lake.

Still, had that space rock, or the one believed to be behind the Tunguska event of 1908, hit an urban area, we could have a major catastrophe on our hands. And, as Lu points out, the only tool we have on hand at the moment to protect ourselves from such a disaster is "blind luck."