Attempting anything at scale in space with chemical rocketry is utterly foolish. Also, even if we put people on Mars, they need a dense, compact, and reliable source of power. Nothing but nuclear engines and reactors even remotely fit the demanding requirements for long-term space activites. A molten salt reactor can be made compact enough to power an airplane, and would be suitable for use in a Mars colony, providing electricity, heat, and production of chemical fuels. The endeavor was scrapped because ICBMs made it obsolete, but the only practical challenge was shielding, and that would not be an issue on mars.
In any case, we have a much greater need to develop the technology here on earth first; nuclear power is the only option capable of providing clean and reliable energy at the scale humanity requires. Until people can accept that, we will continue to waste massive resources on the fantasy of wind/solar, while our reliable power continues to be provided by fossil fuels, or worse yet, by burning trees or other "biofuels".