An assessment of how radiation incurred during a Mars mission could affect food and pharmaceuticals

Radiation levels and associated risks from exposure to galactic cosmic radiation (GCR) during a Mars mission are currently being assessed to protect the health of astronauts. However, the effects of radiation on food and pharmaceuticals that will be stored inside the vehicle during a 3-year journey outside the protection of the geomagnetosphere have yet to be considered. As a first step, we calculated the mean number of charged particle hits and the radiolytic yields in the target materials of freezedried food, intermediate moisture food, and liquid formulation pharmaceuticals that are generally considered to be the most vulnerable form of pharmaceuticals. For this assessment the exterior GCR environment at deep solar minimum was assumed to be uniform, isotropic, and constant throughout the entire round-trip journey to Mars. To obtain the total fluence from a 3-year mission, we multiplied the fluence rates by the mission duration. The annual fluence at the target area inside a Mars transfer vehicle was estimated using a sphere of 10 g/cm 2 -thick aluminum to represent the vehicle. The probability of radiation hits was assessed for a target volume inside the sphere. Additionally, to examine how space radiation may affect taste of food and effectiveness of pharmaceuticals, we simulated yields of the main types of radiolytic species that would be created in liquid water by hits from ions present in GCR. While it is unlikely that GCR causes a rapid change of functional properties in food and pharmaceuticals stored inside the vehicle, it has been suggested that progressive functional defects may occur over time. The functional defects are expected to depend on energy deposition, yields of radiolytic species, bond-dissociation frequency, and any other break-type chemistry. However, the dose received during a 3-year mission to Mars is several orders of magnitude lower than those received for food sterilization or preservation, and the probability of space radiation hitting the individual molecules comprising consumables is very low. In addition it is possible that radiolytic species may not be generated in freezedried food or solid formulation drugs because water has been removed during processing. Therefore, space radiation is certainly not a concern for long-term preservation of food or pharmaceuticals. Temperature change, humidity, and packaging technology are much more challenging issues for food preservation or pharmaceutical stability during long duration missions.