Studies of the radiation environment on the Mars surface using the Geant4 toolkit

Abstract

The radiation environment on the surface of Mars is a potential threat for future manned exploration missions to this planet. In this study, a simple geometrical model was built for simulating the radiation environment on the Mars surface caused by galactic cosmic rays; the model was built and studied using the Geant4 toolkit. The simulation results were compared with the data reported by a radiation assessment detector (RAD). The simulated spectra of neutrons, photons, protons, $$\alpha$$ α particles, and particle groups $$Z=3$$ Z = 3 –5, $$Z=6$$ Z = 6 –8, $$Z=9$$ Z = 9 –13, and $$Z=14$$ Z = 14 –24 were in a reasonable agreement with the RAD data. However, for deuterons, tritons, and $$\,^{3}{\mathrm{He}}$$ 3 He , the simulations yielded much smaller values than for the corresponding RAD data. In addition, the particles’ spectra within the $$90^{\circ }$$ 90 ∘ zenith angle were also obtained. Based on these spectra, we calculated the radiation dose that would have been received by an average human body on Mars. The distribution of the dose throughout the human body was not uniform. The absorbed and equivalent doses for the brain were the highest among all of the organs, reaching 62.0 ± 1.7 mGy/y and 234.1 ± 8.0 mSv/y, respectively. The average absorbed and equivalent doses for the entire body were approximately 44 mGy/y and 153 mSv/y, respectively. Further analysis revealed that most of the radiation dose was owing to $$\alpha$$ α particles, protons, and heavy ions. We then studied the shielding effect of the Mars soil with respect to the radiation. The body dose decreased significantly with increasing soil depth. At the depth of 1.5 m, the effective dose for the entire body was 17.9 ± 2.4 mSv/y, lower than the dose limit for occupational exposure. At the depth of 3 m, the effective dose to the body was 2.7 ± 1.0 mSv/y, still higher than the accepted dose limit.

Modeling the effectiveness of radiation shielding materials for astronaut protection on Mars

“…Previous studies deduce similar outcomes. In particular, [63,56,64] conclude that ∼1 m of regolith shielding provides adequate protection, but increasing the thickness attenuates radiation more gradually; in order to keep effective dose below the safety limits more than 3 m of regolith are required. Mixing regolith with graphite epoxy is proposed by [6], becuase of the hydrogen compounds epoxy contains.…”

Conceptual Architectural Response to Radiation on Mars

“…80-170 m and consists of 50-85% water ice mixed with dust (which reduces its albedo) and rocks [39]. Water ice mixed with <1% of dust and small rocks significantly reduces the albedo; however, albedo particles produced on the planet's surface contribute to the radiation environment [40]. Guo et al [41] claim that this contribution constitutes 19% of the total radiation on Mars.…”