I think Raoul has a good point for the majority of humans, but not the risk taker types likely to tackle Mars. A Mars mission is likely to be far less dangerous than historical missions of exploration. Going to America involved a far greater mental separation from Family and friends in colonial times. Mountain men faced more isolation.

The key psychological factor is reaching a point where the human presence in space is permanent before public apathy sets in again (very dangerous with a been there done that approach). Look at it this way if we could have established a permanent base within 6 Apollo missions we would still be there. In the Mars Direct plan and NASA reference mission each launch is a potential unit of a permanet base or colony unlike the Apollo missions. Those that claim these are more flags and footprints missions are simply not looking at the vast difference in mission capabilities. It is far easier to go from a several year mission to a permanent one than from a few weeks to a permanent one. You can endure a lot off stress and lack of comfort over two weeks but not over several years. I think if you can live in something for years you could live in it indefinitely from a psychological point of view.

A permanent return to the Moon is the common sense next step. It is not the logical next step IMO when you really put a sharp pencil and calculator to work to look at relative costs and really weigh costs versus more subjective evaluations of sustainability.

Regards,
Mark