Miguel C. Ralha
Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto

Abstract
In the past decade, the space exploration spirit has made a significant comeback. In particular, a manned mission to Mars, and even a permanent settlement on this planet has been explored. However, the radiation environment on the surface of Mars is dominated by cosmic rays and secondary particles produced in their interactions with the Martian atmosphere and regolith, making radiation exposure several orders of magnitude higher than that from Earth's surface. This poses a complex problem for any human colony, which, if success is expected, must be fully understood so sheltering solutions can be envisaged. The complex radiation field on the Martian surface and its formation can only be fully understood by using a combination of measurements and model calculations.
To assess the health risks of human exposure to a Mars surface-like radiation field, Monte Carlo simulations were performed using MCNP6 and the ICRP reference male and female voxel phantoms. Initial GCR spectra were generated using the model developed by the German Aerospace Center, DLR. To validate the model, GCR propagation through the Martian atmosphere down to the surface was simulated by following the guidelines of the "1st Mars Space Radiation Modeling Workshop" organized by the MSL-RAD science team. The MCNP6 calculated particle spectra and dose rates were compared to the GEANT4 results of the German Aerospace Center team and the measurements of RAD, and the results were in very good agreement.
After validation, the ICRP voxel phantoms were incorporated into the simulation geometry. The dose equivalent to the different organs and total effective dose were calculated for the time corresponding to the first six months of RAD on the surface of Mars, and for the various incident particles. The directionality and contributions of secondary particles produced by spallation reactions were also assessed.
Possible shelter construction materials on the Martian surface were studied by simulating different material's shielding effectiveness. Also, to mitigate late toxicity caused by exposure to cosmic rays, and by taking into account the maximum permissible doses set for space exploration, daily exposure times for humans on the planet's surface were estimated for possible missions outside the settlement's shelter.

2023 September 20, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
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