summarizes a few of the hurdles of the trip to mars pretty well. You gotta look it up on google, or you can't access it...stupid subscription....but works through google...
Google up: "globeandmail mars The 400-million-kilometre longshot"
make sure you click the article link and not the globe and mail main page.
some points they touch on (they also offer some of the suggested solutions considered):
- Carrying supplies for a 2.5/3 year round trip to mars (food/water/etc)
- breakdown of bone structure
- Radiation in space from the sun (solar flares) and super novas which breaks down food, medicine, etc.
- dust and debris on mars affecting equipment
- mental stability of astronauts as people and as a group
- contamination from mars (when the astronauts come home)
- etc, etc, etc.
A VERY good read.
Another article >> Link -- possible power source for trip to mars