Miners operating among the asteroids will be unable to produce most of their necessary supplies locally. There will thus be a need to import food and… - Robert Zubrin

Thus, the central objection raised against the human settlement and terraforming of Mars: Such projects may be technologically feasible, but there is no possible way that they can be paid for. On the surface, the arguments given supporting this position appear cogent, for Mars is a distant place, difficult to access, and possesses a hostile environment that holds no apparent resources of economic value. These arguments appear ironclad, yet it must be pointed out that they were also presented in the past as convincing reasons for the utter impracticality of the European settlement of North America and Australia.

When a population of organisms grows in a finite environment, sooner or later it will encounter a resource limit. This phenomenon, described by ecologists as reaching the “carrying capacity” of the environment, applies to bacteria on a culture dish, to fruit flies in a jar of agar, and to buffalo on a prairie. It must also apply to man on this finite planet. JOHN P. HOLDREN and PAUL R. EHRLICH Global Ecology (1971) 1 Here is the difference between the animal and the man. Both the jay-hawk and the man eat chickens, but the more jay-hawks the fewer chickens, while the more men the more chickens. HENRY GEORGE

Mars poses a critical test for the human race. How well we handle it will determine whether we remain a single planet–constrained species or become spacefarers with the whole universe open before us.