  A potential crewed mission to Mars would require us to solve a number of
problems, including how to protect astronauts against the devastating effects
of energetic charged particles from Solar and Galactic sources. The radiation
environment on Mars is of particular interest, since maintaining optimal
absorbed doses by astronauts is crucial to their survival. Here, we give an
overview of the conditions on Mars, as determined by theoretical models and
in-situ measurements, and present the main proposed strategies to mitigate
radiation exposure while on Mars. Specifically, we focus on the passive
shielding technique. Several widely used materials, along with some innovative
ones and combinations of those, are studied for their behavior against Solar
Energetic Particle Events and Galactic Cosmic Rays in the Martian environment.
For that purpose, we implement the GEANT4 package, a Monte-Carlo numerical
model developed by CERN, which is specifically applied to simulate interactions
of radiation with matter. A description of our model will be given, followed by
outputs of the numerical model. We conclude that hydrogen-rich materials act as
better attenuators, as expected, but other materials can be helpful against
cosmic rays too.
