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.