  The surface of Mars is bombarded by energetic charged particles of solar and
cosmic origin with little shielding compared to Earth. As space agencies are
planning for crewed missions to the red planet, a major concern is the impact
of ionizing radiation on astronaut health. Keeping exposure below acceptable
radiation dose levels is crucial for the health of the crew. In this study, our
goal is to understand the radiation environment of Mars and describe the main
strategies to be adopted to protect astronauts from the harmful impacts of
cosmic radiation. Specifically, we investigate the shielding properties of
various materials in the Martian radiation field using the Geant4 numerical
model, after validating its accuracy with in-situ instrument measurements by
MSL RAD. Our results indicate that composite materials such as types of
plastic, rubber or synthetic fibers, have a similar response against cosmic
rays and are the best shields. Martian regolith has an intermediate behavior
and therefore could be used as an additional practical option. We show that the
most widely used aluminum could be helpful when combined with other low atomic
number materials.
