The moon exploded without warning and for no apparent reason. The time would later be referred to as A+0.0.0 or simply Zero: 05:03:12 Coordinated Universal Time. The hour of Zero. After the explosion of the moon, a meteor storm rages for millennia, transforming the Earth's surface into an uninhabitable wasteland. To save humanity from extinction, the nations of Earth send a fleet of arks into space. The asteroid Amalthea, originally docked at an international space station for research purposes, is to serve as a shield for the colony. However, life in space takes a heavy toll, and the survival of human civilization hangs by a thread.