  The impact of exposure to astrophysical ionizing radiation on astronaut
health is one of the main concerns in planning crewed missions to Mars.
Astronauts will be exposed to energetic charged particles from Galactic and
Solar origin for a prolonged period with little protection from a thin
spacecraft shield in transit and from the rarefied Martian atmosphere when on
the surface. Adverse impacts on astronaut health include, for example, Acute
Radiation Syndrome, damage to the nervous system, and increased cancer risk. We
rely on medical studies to assess the impact of enhanced radiation dose levels
on various physiological systems and the overall health of astronauts. Using a
combination of radiation measurements and numerical modeling with the GEANT4
package, we calculate the distribution of radiation dose in various human body
organs for various expected scenarios simulated with a model human phantom. We
suggest mitigation strategies, such as improved ways of shielding and dietary
supplements, and make recommendations for the safety of astronauts in future
crewed missions to Mars.
