I know this sounds like a 3d printing question, but it is more space oriented so bear with me.
My reasoning for this post is that the Martian soil is comprised mainly of iron oxide, which gives it its famous rusty reddish color, and is abundant nearly everywhere you go on the surface of Mars.
I was wondering, would it be possible to use Martian soil as material for a 3d metal printer?
A selective laser sintering machine using a laser to machine parts out of iron oxide doesn't seem very farfetched to me. Selective laser melting could also be used. Furthermore if even more fine machining is necessary laser polishing and/or laser engraving could be used.
Considering a nuclear reactor might be sent to Mars before any astronauts even leave the ground they would have a nearly limitless and powerful source of electricity waiting for them on Mars, thus allowing for arbitrarily powerful lasers to be implemented. A strong enough laser would probably do what a blast furnace does to iron oxide on Earth nearly instantly, burning off any undesired materials in the process.
Modules and other devices built out of interchangeable parts would allow for these things to be made on Mars, for either building, repairing, or upgrading critical systems.
The module containing the 3d selective laser sintering/melting printer would probably be very light, and since certain parts could be machined on Mars they wouldn't have to take those parts from Earth, reducing launch loads considerably (so long as the mass that they save is less than that of the 3d selective laser sintering/melting printing module).