Did ancient extremophiles survive the first apocalypse?

With the threat of nuclear annihilation hanging over their heads, governments, companies and even individual families invested in fallout shelters during the 1960s. If worst came to worst, they could descend into their provisioned holes and hope to eventually emerge to reclaim a ravaged world.

Yet even the worst scenarios for man-made Armageddon at the time couldn't hold a candle to what Earth endured approximately 3.9 billion years ago, during the Hadean Eon. Due to a little orbital readjustment among our solar system's gas giants, our planet was pelted with a barrage of meteor strikes. The damage was catastrophic, melting the surface to magma. Our oldest rocks formed in these days, and the earliest signs of life emerged in the wake of the destruction -- or so we've long believed.

Our entire planet is only thought to be 4.6 billion years old, and no one is arguing that vast cities covered the planet in those days. Still, A New Scientist article published today explored the possibility that life as we know it didn't simply emerge in the aftermath of this Hadean upheaval, but actually weathered the brutal celestial storm. The article points to a recent study from the University of Colorado Department of Geological Sciences that high-temperature extremophile microbes, such as those that thrive today, could have theoretically survived in the depths of the Earth.

If this theory holds true, it means life on Earth could have emerged 4.4 billion years ago, after the formation of the planet's oceans. For that matter, what ancient forms of life might thrive down there now, just waiting for us to sink an oil drill into its subterranean lair?

Get lost in the subworlds at HowStuffWorks.com: How Fallout Shelters Work How the Earth Works How Extremophiles Work How Space Collisions Work