Second mars has a weak magnetic field, unlike earth being protected by its huge magnetic field. mars has a very small and weak one.
having a magnetic field protects us from solar flares and solar radiation sun produces. and when mars got hit by a solar radiation even with
the most advance protection agains radiation we have it will be useless resulting to instant death.
Doesn't Mars have some areas that are better protected than others? I think the idea was that they were going to use one of those to settle in since it provided adequate protection.
Even if there are it won't d any good if its in the surface.and if your tal,king about digging underground it will take time. Thus they'll need more funding which they will not have. And it will take more than a decade to just to send one rover that will be able to dig underground. But still I'm looking forward if they will be able to set a colony on mars.