Hello Mark -

The limits imposed on manned flight to Mars by radiation are not "mine", and they weren't even pointed out by me - they were pointed out by those who are responsbile for astronaut safety.
I myself was extremely sceptical at first about the problem radiation presented, but facts area as facts are... This new material may present a significant aid in dealing with those problems, and hopefully will be useful for manned Moon flight as well.

One thing is definite, however. Mars lacks much of magnetic field, and thus lacks much protection against radiation. This definitely places severe limits on terra-forming, and thus on the final value of Mars to people. While how severe these limits are remains to be seen, they simply can not be ignored.

ep