Space Radiation Remains Major Hazard for Humans Going to Mars
▻http://www.wired.com/2014/04/radiation-risk-iss-mars
People living in the U.S. are exposed to about 3 millisieverts of radiation from natural background sources each year (millisieverts are units of radiation exposure in the human body). A nuclear accident, like Fukushima, might raise this by about 1 millisievert. An astronaut on a round-trip, two-and-a-half-year Mars mission, by contrast, can expect to receive around a sievert of cosmic ray radiation, nearly 1,000 times more.
[…]
Cucinotta estimates that an astronaut’s lifespan after exposure to radiation on a Mars trip would be shortened between 15 and 24 years from the average.
[…]
Before humans are sent to the Red Planet, NASA should do a focused decade-long study on all the potential health problems that radiation could cause. Hopefully, this would bring up new ways to combat some of the worst effects.