Kara Zor-El is the last survivor of Argo City of the planet Krypton. Although Argo, which had survived the explosion of the planet, drifted through space as a self-sustaining environment, the soil of the colony eventually turned into Kryptonite; and though Kara's father Zor-El placed lead sheeting above the ground to protect the citizens from radiation, meteorites pierced the sheeting, and the Kryptonians died of radiation poisoning instead of replacing the metal.
