[1457389]

I don't think you have looked very hard then. Here's Zubrin on the topic:

>However, we already have data that shows that the accumulation of slow rates of cosmic ray radiation received during long duration spaceflight is not a showstopper for human Mars exploration. GCR dose rates in low Earth orbit are about half those in interplanetary space. Thus, there is a growing number of cosmonauts and astronauts who have already received Mars mission equivalent GCR doses during extended space missions without any radiological casualties.

~http://www.thespacereview.com/article/2749/1

He mentions in a recent speech that the most deleterious effect of time spent in space is related to zero gravity, not radiation - and that can be fixed with resistance training.

[wott]

You talk about a Mars exploration mission, hence a relatively short time duration, not about settling and living one's whole life on Mars.

[nickik]

How about one problem at the time. If we can actually go there with lots of stuff, stay for a long period and come back we will already have made more progress then most people thought possible.

We know most of the physics needed to deal with the situation, if we can get equipment to mars. Radiation is a problem, but its not Problem Nr. 1.