inhabitants of the moon and Jax-Ur became the first and only criminal to be banished eternally to the Phantom Zone. This disaster also prompted the Science Council of Krypton to ban space flight completely. Survivors A Silver Age Superman was not alone in the survival of Krypton's destruction, being joined by his cousin Supergirl, the Phantom Zone criminals, Krypto the Superdog, Beppo the Super-Monkey, a juvenile delinquent named Dev-Em, the entire population of the city of Kandor, Supergirl's biological parents, and even Superman's biological parents (in hibernation on a space ship - Superboy #158 (July 1969)), although it was discovered that they actually died from lethal radiation. When the planet exploded, one entire city of Krypton, Argo City, survived the cataclysm. Argo City drifted through space on an asteroid-sized fragment of Krypton, which had been transformed into kryptonite by the explosion. The super-advanced technology of its Kryptonian inhabitants allowed them to construct a life-sustaining dome and a lead shield that protected their city from the kryptonite radiation of the asteroid. The protective shield was destroyed in a meteor storm, exposing the inhabitants to the deadly radiation. The sole survivor of Argo City, Kara Zor-El, was sent to Earth by her scientist father to live with her cousin Kal-El, who had become known as Superman. Kara adjusted to her new life on Earth and became known as Supergirl. It was later discovered that Supergirl's parents had survived in the Survival Zone, a parallel dimension similar to the Phantom Zone, from which she released them. When the bottle city of Kandor was finally enlarged on a new planet that was similar to Krypton, Supergirl's parents joined its inhabitants to live there. Daxamites The people now known as the Daxamites were originally Kryptonians who left their homeworld to explore the universe (in post-Crisis on Infinite Earths continuity, the Eradicator, an artificial lifeform programmed to preserve all Kryptonian culture, altered the birthing matrices ("artificial wombs") that the explorers took with them so that all newborns would be fatally vulnerable to lead and other materials such as greenhouse gases and certain rocks). Thus, if they persisted in their anti-Kryptonian wanderlust, they would all die from it. One Daxamite, Mon-El, was poisoned by lead and preserved in the Phantom Zone until a cure was found by Brainiac 5 in the 30th century, whereafter Mon-El became a member of the Legion of Super-Heroes. Crisis on Infinite Earths