PreCambria

Four Billion Years Ago.
Earth has just recovered from the biggest catastrophe in its history- the formation of the moon. As the remaining fragments of the Gaia-Theia collision gather above, they are disturbed by yet another force. The rest of the solar system is still taking shape as well, and trillions of tons of debris are still scattered in the empty space between. Even taking into account Earth's 27-quadrillion square miles of orbit, there's simply too much for it to all stay in space.
While it will never get as close to destruction as it did just four hundred million years earlier, this period of heavy bombardment holds the key to life on Earth. The denser materials rain from the sky, generating the heat and energy required to cause reactions. In water, these will form essential proteins- carbon compounds and molecules that will eventually manifest in the first microorganisms.
Life as we know it is on its way.

Rendered in Photoshop