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How are asteroids and bacteria on Earth related?

Asteroid All Mighty? Nacivet/Getty Images
Asteroid All Mighty? Nacivet/Getty Images

Religious accounts of life's origins tend to favor a little outside influence. A divine hand reaches down from the sky, perhaps, and stirs this biology into existence.

As fantastic as this sounds, scientist consider a similar god-free possibility in the form of panspermia.

Panspermia theory holds that life didn't originate on this planet at all, but traveled here on an asteroid some 4 billion years ago. This vital fragment might even have originated on Mars, blasted off the surface by a primordial bombardment of cosmic bodies.

See, bacteria are some tough mama jamas, capable of thriving in extreme conditions -- including a jaunt through the harsh void of outer space.

So think of our planet as a huge Petri dish, filled with excellent fodder for life. An incoming asteroid is like a q-tip coated in bacteria. Get the idea? The seed of life travels from one environment to a new one, and there thrives into a new ecosystem.

We call this theory exogenesis, the notion that life on Earth originated elsewhere in the universe.

About the Author: Robert Lamb is a senior writer and host at HowStuffWorks, where he co-hosts Stuff to Blow Your Mind. An avid science enthusiast, he boasts a deep love for monsters and a hankering for electronic music.

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