Also, it is important to note that without several decades of rudimentary, relatively easy terraforming, early settlements will not look like the image above. Surface solar and cosmic radiation will force early settlements underground (either buried beneath several meters of soil or tunneled into mountainsides).  Space activists favoring other destinations than Mars often deride such artists concepts as “fantasy”…the most realistic depictions of early settlements show only airlocks and telerobots on the surface, with cross-sections of extensive subsurface environments.