First, colonizing Mars does not constitute interstellar colonization. Second, i did not say that we have to bring anyone back, but certainly we would initially be setting up a base station, from which i suspect the original crews would, sooner or later be brought back.
I said that this is
one of the reasons i find the Fermi paradox naive. The other is that it ignores the cost (although, obviously, that cost is in resources and energy, it is not unreasonable to think of it in terms of dollars) which will be entailed to protect large numbers of people over the time required to get them to Mars with all of the material they will need for survival. Mars is probably a good candidate for colonization, just because the cost would be manageable. That would not necessarily be the case with an attempt at interstellar colonization. But with Mars, there is no magnetic field to protect colonists from cosmic radiation, so it would be necessary to locate them and all of their food production resources underground, which would greatly increase the cost.
But, as i say, it's still probably the best candidate.
