Re: Risk of cancer doubles?
Nope from 6 percent to 12% for death and double for getting a radiation induced cancer. These cancers occur earlier in life than background types and are more aggressive. So if 6 person Mars crew one dies in their early 60's from space radiation and 1 other gets a radiation cancer but treatment is successful. So not quite a one-way mission for the 4 persons not impacted. Maybe invest in development of countermeasures to lower the 12% a bit would be smart.
But their cognition including memory are degraded also from space radiation so may not remember they went to Mars 10 to 20 years earlier.