>If we reach the point where Mars has a worthwhile industrial base, Mars becomes the launch pad for just about everything. The weaker gravity combined with the thinner atmosphere (so you can fly vacuum optimized engines from the surface) makes it a good order of magnitude cheaper to launch mass from. For large structures destined for Earth orbit, it would eventually make sense to build them on Mars and fly them into Earth orbit.

But you could say the same of the moon, right?