Mars is the unrealized frontier which brings hope to human minds, and it pays the price for this with human colonization. It is largely representative of the American frontier, and Bradbury draws many parallels between the colonization of Mars and the European conquest of the Americas. While it is a symbol of hope, and unrealized human potential that allows Bradbury to explore how the drive for such horizons motivates the human mind and activates human nature, it also is a symbol of the degradation and destruction faced by the Martians. Their lingering presence, and that of their cities, much like the way Indigenous peoples are utilized in stories of the Western frontier, complicates the moral dimension of the colonizers, forcing the reader to come to terms with the consequences and ravages of so much unbridled settler expansion.

According to the legend of Prometheus, fire is the very first technology humanity masters. Bradbury ties this earliest technology to the most powerful technology in the collection—rockets—in the very first vignette, and the symbol of the rocket and the fire motif complement each other throughout the work. Fire is both positive, fueling the rockets which bring an intellectual summer to Earth in “The Rocket Summer,” and negative, as it consumes the last marker of human achievement, having ravaged the Earth in “There Will Come Soft Rains.