Everything you wanted to know about space radiation but were afraid to ask

Abstract

The space radiation environment is a complex combination of fast-moving ions derived from all atomic species found in the periodic table. The energy spectrum of each ion species varies widely but is prominently in the range of 400-600 MeV/n. The large dynamic range in ion energy is difficult to simulate in ground-based radiobiology experiments. Most ground-based irradiations with mono-energetic beams of a single one ion species are delivered at comparatively high dose rates. In some cases, sequences of such beams are delivered with various ion species and energies to crudely approximate the complex space radiation environment. This approximation may cause profound experimental bias in processes such as biologic repair of radiation damage, which are known to have strong temporal dependencies. It is possible that this experimental bias leads to an over-prediction of risks of radiation effects that have not been observed in the astronaut cohort. None of the primary health risks presumably attributed to space radiation exposure, such as radiation carcinogenesis, cardiovascular disease, cognitive deficits, etc., have been observed in astronaut or cosmonaut crews. This fundamentally and profoundly limits our understanding of the effects of GCR on humans and limits the development of effective radiation countermeasures.

Dose-Effects Models for Space Radiobiology: An Overview on Dose-Effect Relationships

“…Most epidemiologic data results from the astronaut cohort are from exposures incurred on missions during the Space Shuttle era, where <100 mSv was accumulated by an astronaut. Nevertheless, the nominal mission length for astronauts has increased to at least 6 months in duration with exposures of 1 mSv to 1.5 mSv per day, depending on the phase of the solar cycle, the number of spacewalks performed, and the level of solar activity ( 81 ).…”

The Impact of Ions on DNA

“…The interaction of radiation with DNA's electronic structure is a complex process [2,3]. The numerical models currently used in radiobiology and clinical radiotherapy do not capture the detailed dynamics of these interactions at the atomic level.…”

The Blood-Brain Barrier in Space: Implications for Space Travelers and for Human Health on Earth

“…Direct pathways involve ionization of DNA, RNA, proteins and lipids. Indirect damage results from generation of reactive oxygen species (Fauquette et al, 2012;Chancellor et al, 2021). Radiation damage can lead to necrosis, apoptosis, autophagy, or senescence (Allen and Limoli, 2022).…”

“…In addition, all the above mentioned spaceflight studies were conducted in LEO. Thus, it is difficult to estimate how and to what extent space radiation would affect human tissues in deep space, beyond the protective shield of the Van Allen radiation belts (Chancellor et al, 2018;Chancellor et al, 2021). For instance, if intense space radiation increases the penetration of blood-borne proteins into the brain, the results may be seizures.…”