Important "experiment" regarding radiation
See Ed wrights post at Return to Moon board:
http://www.space-frontier.org/cgi-bin/BBS/MoonBase/read/9603
This changes the assumotion that any radiation is harmful and shows that heighten radiation level over long term may have a health benefit.
Now, this radiation is different than high energy particle type radiation that could be a problem with a Manned Mars transit and on maritian surface living, but I still think it does indicate that Manned Mars might be possible at a lower cost and risk.