Reality check on Mars colonies

Hard to see the longterm appeal of any habitat that doesn't somewhat recreate a terrestrial environment. If you want a colony that's a cross section of humanity, from all walks of life, it would probably include a fair number who aren't interested in living underground all the time. The problem with Green's terraform scheme is not just gases, but the solar wind deflector. Another ex-NASA guy, David Hammen, estimated you would need a terawatt to maintain the magnetic shield at around Earth equivalent of 0.5 Gauss. Something like 50 Three Gorges Dams.

Well, it doesn't appeal to me, but clearly there are people who do find the prospect enticing. Could be good to visit - although even that looks un-enticing - but living there? No.

I think too much of the enthusiasm relies on false expectations. Whether Mr Musk is sincere in his Mars ambitions or not I am convinced he is not going to push SpaceX into bankruptcy with unworkable colony attempts; I suspect he would much prefer SpaceX do Mars missions as contractors to taxpayer funded missions, that SpaceX gets paid to do. I'm not convinced that being misleading about the prospects, to sustain popular support for taxpayer space programs that use contractors is entirely ethical. The principle commercial opportunities in space are all local to Earth, servicing Earth needs and Earth customers. Much of that is taxpayer funded contracts. Beyond that is ONLY taxpayer funded contracts.

If it is commercial potential we look for - and I think nothing less will kickstart anything in space that will be self-sustaining - then asteroid nickel-iron is the standout space commodity of value and interest. I'm not convinced the economics of space station living will be much better than Mars, but a mining/refining operation will likely make things like stockpiles of excess iron and nickel (leftover from extracting PGM's) as well as carbonaceous material, water ice, silicate rocks, sulphides, all that could be put to other uses. A space colony wouldn't be self supporting there either but with access to those it may have much reduced start up costs.

Actually, the moons of Mars have more appeal to me than Mars itself - combining ongoing study of Mars with studying objects that are, for all intents and purposes, asteroids. For a viable space economy the significance of planets may be for resources that are important but only occur in useful concentrations where hydro-thermally active planetary histories have occurred, ie Earth and possibly Mars. I suspect Uranium or other fissionable elements would be an example, ie asteroids may not have everything an advanced economy requires either.
I don’t disagree that the economics of Mars missions is dire. But there are tangible scientific benefits to space exploration, not just in aerospace but many scientific disciplines. NASA has its Spinoff publications as part of their Technology Transfer Program. I’ve found some interesting reading in there.

I don’t see why a Mars mission wouldn’t provide the same technology transfer benefits that Lunar, Earth orbit and robotic probe missions do.