Everything You Wanted to Know About SpaceRadiation but Were Afraid to Ask

TL;DR

This paper discusses the complexity of space radiation, challenges in simulating it on Earth, and how current experimental limitations may lead to overestimating health risks for astronauts.

Contribution

It highlights the limitations of ground-based experiments in accurately replicating space radiation and their potential impact on risk assessment and countermeasure development.

Findings

Current ground experiments use high dose rates and simplified ion spectra.

Such experiments may introduce biases affecting biological repair process understanding.

No primary space radiation health risks have been conclusively observed in astronauts.

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 dependancies. It is possible that this experimental bias leads to an overprediction of risks of radiation effects that have not been observed in the astronaut cohort. None of the primary health risks presumely attributed to space radiation exposure, such as radiation carciogenesis, 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.