The main thing is the population and even scientific american magazine said in there dec. 2000 issue that the population would be 41 billion at normal growth by 3000ad. My belief is that everything is put on earth s for the universe for a reason. And if so than maybe mars is there for us to use, considering it is the only planet that is in a distance from sun in order to substain human life other than earth. Others are to close our to far and besides everything on mars is practical the same with its axis degree, its rotation period, and range of temperatures.
Lets face it that it's just like chistopher columbus and the new world.
A place unknown but with great potential. Then you could form it so it would cover the whole planet as if you were building a giant epcot center except each sheet could cover say 4 football feilds in width, then maybe in lets say 100 years it could be completed. After you have completed the sphere then with injection ports you could feed the planet. Maybe with some kind of ammonia nitrate or of some other abundant material. I know it takes ammonia nitrate to become 800 degrees with eletrical charge thru platinum wire to become water and nitrogen gas, but lets talk about that later.