Man, the whole Mars thing really irks me. I have yet to see any Mars colonization plan which accounts for galactic cosmic radiation (heavy ions traveling at 99+% the speed of light which suffuse space outside of low Earth orbit). Traditional radiation shielding is not very effective against them and in some cases can make their biological effects worse—the particles hit the shielding and turn into a shotgun blast of high-energy decay products which are even more likely to interact with the non-relativistic atoms like, say, astronaut DNA. I will not take anybody's proposals for colonization of another solar body seriously until they have a real answer to this problem, and I urge you not to either.

"During transit outside of LEO, every cell nucleus within an astronaut would be traversed, on average, by a hydrogen ion every few days and by heavier HZE nuclei (e.g., 16O, 28Si, 56Fe) every few months. Therefore, in spite of their low flux, HZE ions constitute a deleterious biological threat and contribute a significant amount to the cumulative GCR dose that astronauts will incur outside of LEO."[0] (emphasis mine)

These particles are everywhere, they come from no specific direction (hence the designation "galactic"), and represent a significant threat to any living creature in deep space. To avoid them during long-term occupation of the Moon or Mars, we'd have to live deep underground. By some estimates, even a one-way trip to Mars could prove fatal to a significant percentage of those taking the journey.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4206856/