Researchers at the Medical College of Wisconsin published a study in PLoS One on Oct. 14, 2026 examining how deep‑space radiation and weightlessness affect astronaut health for a Mars mission.
At a 1.5 Gray dose, rats showed perivascular fibrosis—scarring around blood vessels—around coronary vessels; 270 days after exposure the fibrotic area had doubled, constricting the vessels and markedly increasing heart‑attack risk. When rats received a lower dose approximating the cumulative radiation expected for a three‑year Mars mission, the researchers observed no immediate scarring, but after one year 83 % of the animals exhibited perivascular fibrosis, suggesting the effect may manifest only after decades in humans.
Months after irradiation, rat spleens had lost approximately two‑thirds of their Natural Killer (NK) cells—a white blood cell important for immune function—while rats exposed only to hindlimb unloading recovered normal NK levels; combined radiation and unloading showed impaired recovery, indicating radiation hampers bone‑marrow response to stress.
Genome sequencing of white blood cells revealed permanent mutations in genes associated with Clonal Hematopoiesis of Indeterminate Potential (CHIP) 235 days after radiation exposure; on Earth CHIP correlates with higher leukemia risk and a four‑fold increase in heart‑attack and stroke risk due to heightened arterial inflammation. To mimic weightlessness, scientists used hindlimb unloading (HLU) on middle‑aged rats, lifting their back legs off the ground at a 30‑degree angle with a tail‑attached harness for thirty days.
Scientists simulated radiation exposure at Brookhaven National Laboratory’s NASA Space Radiation Laboratory using a five‑ion, six‑beam cosmic ray simulator called simGCRsim that delivers high‑speed protons and heavy ions such as silicon and iron. The experimental protocol consisted of five days of hindlimb unloading, a few minutes of high‑dose radiation intended to represent months of space exposure, followed by another 25 days of hindlimb unloading, after which the researchers monitored the rats for about one year, which the authors equate to roughly 25 human years.
The authors note limitations: they administered the radiation dose acutely rather than chronically, leaving uncertain whether cellular repair could alter outcomes, and the study used only male rats, so findings may not apply to females.
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