Mars to Stay to 30, thereby beginning a Martian settlement. Since the Martian surface offers all the natural resources and elements necessary to sustain a robust, mature, industrialized human settlement—unlike, for example the Moon—a permanent Martian settlement is thought to be the most effective way to ensure that humanity becomes a space-faring, multi-planet species. Through the use of digital fabricators and in vitro fertilisation it is assumed a permanent human settlement on Mars can grow organically from an original thirty to forty pioneers. A Mars to Stay mission following Aldrin's proposal would enlist astronauts in the following timeline: As Aldrin has said, "who
The Gods of Mars to Earth in pre-technological eras, particularly with the inclusion of kingdoms, empires or religious societies. Spacecraft may appear, but are not central to the story (something which makes these tales distinct from Space Opera, where spaceships are usually a key focus of the narrative). There were some Planetary Romances prior to the publication of the Barsoom novels, but "A Princess of Mars" and "The Gods of Mars" and other novels in the Barsoom series were the most influential on the numerous similar stories that were published subsequently. Burroughs's vision of Mars was loosely inspired by astronomical speculation of the time,