The dream of human exploration of Mars is intimately tied to the belief that new lands create new opportunities. In human history, migrations of people have been stimulated by overcrowding, exhaustion of resources, the search for religious or economic freedom, competitive advantage, and other human concerns. Rarely have humans entered new territory, then completely abandoned it. In the past, there have always been a few people who were adventurous enough to adopt a newly-found territory as their home. Most of these settlements have eventually become economically self-sufficient, and have enlarged the genetic and economic diversity of humanity. The technological revolution of the 20th Century, with high speed communication and transportation and integrated economic activity, has reversed the trend toward human diversity; however, settlement of the planets can once again enlarge the sphere of human action and life.
The settlement of Mars presents new problems and challenges. Principal among these is the absence of a livable natural environment. That, and the current high cost of transportation are the main barriers to human expansion there. The fact that humans, once on Mars, can not easily return to the Earth, and then only at specified times approximately 26 months apart, makes it necessary to develop systems with high reliability and robustness. The creation of a livable, artificial environment, is technically feasible. The high cost of transportation will ultimately be reduced. The Reference Mission is not a program to settle Mars; however, the objectives of the Reference Mission are to establish the feasibility of and the technological basis for human settlement of the planet.