Hibernation and space radiation protection: assessment of simulated galactic cosmic radiation pathology in hibernating mammals

Introduction: Among the hazards of travel beyond low earth orbit (LEO) for humans is exposure to space radiation, composed of charged particles from solar particle events, and galactic cosmic rays. Long-duration missions beyond LEO therefore carry substantial risks, ranging from acute radiation sickness and immune dysfunction to more long-term increased risks of developing cancer and neurodegenerative diseases. NASA limits astronauts’ career exposures to space radiation to 600 mSv. As future deep-space missions are projected to exceed this exposure limit, developing new and effective protective measures against space radiation is an urgent priority. Hypothesis: Hibernating mammals are known to tolerate gamma-ray exposure during hibernation better than those that do not hibernate (e.g., rats), suggesting that hibernation may hold key mitigative mechanisms for space radiation. However, galactic cosmic radiation differs significantly from radiation on Earth, and to date, hibernation has not been assessed for protection from simulated galactic cosmic radiation (sGCR). Given precedential information from ground studies, we hypothesize that hibernating mammals will have protection from radiation-induced pathologies associated with long duration space travel. Methods: In this study, we aimed to broadly examine 13-lined ground squirrels, a hibernating rodent, exposed to simulated low dose/chronic sGCR using californium-252 (252Cf) which produces high linear energy transfer neutrons coupled with photons. Animals were exposed for 6 months at ~1-2mSv sGCR/day in both the hibernation and active seasons designed to mimic dose rates in deep space. We are examining numerous endpoints including metabolomic, proteomic, and genomic changes along with mitochondrial function, telomere length dynamics, cardiac and ventilatory function, vascular function and histological changes. Our overall goal is to determine whether hibernating animals are protected from sGCR pathologies and, if so, to identify the nature of such protection. Results: Preliminary results indicate notable changes in the hibernation phenotype of sGCR-exposed animals. Irradiated animals showed significant body mass reductions (~35% drop in mass compared to ~24% drop in mass in controls; p< 0.05) and reductions in torpid body temperatures. Spontaneous arousal from hibernation, a natural event that accounts for the majority of energy use in hibernation, appears to be similar between the control and irradiated hibernators. This suggests that mass change differences are likely due to a higher torpid metabolic rate in sGCR exposed animals. Bone mineral density was unaffected by sGCR in both active and torpid animals. NASA grant #80NSSC24K0650, SRE, HRP, NIAC This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.