Free Astronomy Magazine September-October 2019

43 SEPTEMBER-OCTOBER 2019 ASTRONAUTICS S upernovae, like the one depicted below, are the main sources of galac- tic radiation that enter our Solar System and di- rectly affect the spacecrafts that travel beyond the magnetosphere. [ESO/M. Korn- messer] All of these experimental inconsistencies and various other environmental consider- ations give uncertainty to the results of space radiobiology studies, making them only partially usable for extrapolating and predicting the clinical consequences for as- tronauts. This is not encouraging, as health risks associated with exposure to space ra- diation will become even more relevant when future manned missions require transfers far beyond low Earth orbit and well beyond the protection of our magne- tosphere. So far, only 27 astronauts have exceeded these limits – all during the Apollo program – and have done so only for a few days, a statistically negligible sample for providing meaningful informa- tion about the effects of space radiation on the human body. About 530 astronauts have operated in low Earth orbit for ex- tended periods, where only long and/or re- peated stays can be considered risky (50 astronauts have exceeded 330 days aboard space stations). Despite the protection offered by the mag- netosphere, an astronaut in orbit accumu- lates about 200 times more radiation than an airline pilot or a nurse in a radiology unit. On a mission to Mars, astronauts would be subjected to a dose of radiation 700 times