What are the dangers from radiation in transit and on the surface of Mars?
Life on Earth is actually exposed to constant background radiation; as such, humans actually require some radiation to live. For example, someone living near sea level in the United States is exposed to roughly 150 millirem (where 1 rem is the standard unit of radiation measurement in the US, a millirem is one thousandth of a rem, and 1 Sievert, the European measure of radiation, is 100 rem), per year and those living in high-elevation locales such as parts of Colorado receive 300 millirem annually due to the smaller amount of atmosphere shielding them. Radiation only becomes dangerous when absorbed in large quantities, particularly so if those doses come over short periods of time. A prompt dose, such as would be delivered by an atomic bomb or a meltdown at a nuclear plant, can be as high as 75 rem without any apparent effects. Longer-term doses have much lower effects: according to the National Academy of Sciences National Research Council, a dose of 100 rem causes a 1.81% increase i
