Aliens Among us?

Ahhh! A comet hits the earth! Life as we know it is wiped out.

It's the stuff of disaster movies like 1999's Deep Impact -- and the plot for more than one Star Trek episode. Scary.

But if comets could spell our demise, it turns out they could also have been the cause of our existence in the first place.

Here's how it could work.

4.5 billion years ago, right after the Big Bang, comets formed. Meanwhile, our solar system was probably formed as the result of the explosion of a supernova. According to an article in Science Daily, "The supernova injected radioactive material such as Aluminium-26 into the primordial solar system and some became incorporated in the comets…. the heat emitted from radioactivity warms initially frozen material of comets to produce subsurface oceans that persist in a liquid condition for a million years."

In other words, back at the beginning of the universe, comets in our solar system had cores of warm, liquid water. Some still have watery cores.

And as any sci fi geek knows, liquid water is the one critical element for the creation of Life As We Know It.

Could microscopic life nurtured in the warm, watery core of a comet have created life on Earth? This theory, known as cometary panspermia, has some supporters in the scientific community. Professor Chandra Wickramasinghe and his colleagues at the Cardiff Center for Astrobiology are convinced that the idea is correct.

So the theory of cometary panspermia, like comets themselves, may just hold water.

(Photo courtesy of European Space Agency)