[Expectant_Philosopher (OP)]

The theory on travel to Mars is to send modules and supplies to Mars in advance of humans to use by travelers to survive on once the travelers arrive.  The theory is that all the materials they need must be shipped to Mars.  Can we change that theory to use processes as Arthur C. Clarke's "Rendezvous with Rama" espoused, that of automatic build processes that create what inhabitants need to survive?  Using current technologies we can actually 3-D print structures and devices.  On Mars we could build cites using remote automation.  We can send the automation to Mars to construct structures, to build power generation stations, to manufacture functional devices.  Then once the automation notifies completion, our voyagers can venture out and arrive at fully operational sites, increasing their chance for success - for survival.

[CliffordK]

I think a lot could, and should be manufactured on Mars, or any planet or moon that is to be colonized. 

Undoubtedly there would be a benefit of building things like a greenhouse before actually arriving on Mars. 

Like Earth, much of the Martian crust consists of metal-oxides.  Extracting metals such as Iron and Aluminum would have the secondary benefit of releasing oxygen. 

I'm not sure you would wish to "print" a large structure.  But, one could imagine robot constructed buildings. 

I believe that much of the small 3-D printing that is currently being used is with plastics.  Unfortunately, carbon, which would be the primary ingredient for plastics may not be as abundant as other minerals, although there is some evidence for dry ice in places, as well as water ice.

Any habitable structures would have to be engineered for an extreme environment, with high pressure inside, low pressure outside.  Leak-proof.  And, able to endure a warm interior, and brutal cold exterior, along with extreme daily temperature changes.  If one is using solar energy, then one would need to heat the structure, and maintain the heat using a minimum energy input, and be able to endure dust storms for up to several months.

While some construction techniques may be effective with a deposition technique, for example the use of spray foam, other  construction techniques may not.  For example the use of rebar and wire mesh likely would be prefabricated and inserted into the structure. 

The question is how much it will take to send the tools to do basic smelting and concrete work to Mars.  Or the basic tools that one can use to build progressive larger and more complex systems with. 

Keep in mind that any remote control must deal with a bidirectional (4 to 20 light minute) transmission delay.