There are so many reasons human colonisation won't happen- 1. Cost- obvious, unless a technology revolution occurs, soon! 2. Danger- no atmosphere, no van Allen belt, no protection from solar radiation or flares 3. Time factor- journey time, radiation exposure, bone mass loss, etc. 4. Global warming- in the near future will require most of civilisation's wealth to combat 5. Resource depletion- making hardware costs increase exponentially 6. Additional to 3. Civilisation is running out of time, can't agree on what to do 7. Psychological- The biggest problem of all; a small group isolated from all that Earth offers; beauty, freedom to wander, landscape, family, sea/air/colours/wildlife etc, etc. To live permanently in a completely hostile environment, confined to a greenhouse, utterly desolate and boring scenery, sensory deprivation, no chance of rescue or return. Recipe for depression, madness and suicide!