Set in the then-distant future of 1973, It! The Terror from Beyond Space depicts an era where the United States has achieved routine manned interplanetary travel. The narrative centers on a rescue mission to Mars to recover Colonel Edward Carruthers, the sole survivor of the first expedition. The film envisions a space-faring culture that utilizes multi-level rocket ships with vertical layouts, central access shafts, and dedicated cargo bays, reflecting an optimistic 15-year leap from the film's 1958 production date to its 1973 setting.

Earth functions as the undisputed political and scientific hub of this future, managing missions via a centralized "United Space Group." However, the social dynamics depicted for 1973 remain strictly rooted in the 1950s; despite having female scientists and doctors aboard the vessel, they are largely relegated to domestic chores like serving coffee and clearing dishes for their male counterparts. This cultural stagnation stands in stark contrast to the rapid technological advancement assumed to occur in the intervening years.

In terms of technological predictions, the film correctly identifies the challenge of Martian survival but inaccurately predicts the presence of a humanoid Martian civilization. The film's resolution hinges on oxygen consumption rates and the use of airlocks for vacuum-based extermination—a tactic that would become a staple of the genre. While the 1973 timeline for Mars colonization was wildly over-optimistic, the film's use of nuclear pile reactors to power ships prefigured real-world research into nuclear thermal propulsion like NERVA. Ultimately, the film concludes that Mars is too hostile for immediate colonization, a sentiment that echoed real-world space race pivoting away from Mars toward the Moon in the actual 1960s and 70s.