How safe is safe enough? Radiation risk for a human mission to Mars

PLoS One. 2013 Oct 16;8(10):e74988. doi: 10.1371/journal.pone.0074988. eCollection 2013.


Astronauts on a mission to Mars would be exposed for up to 3 years to galactic cosmic rays (GCR)--made up of high-energy protons and high charge (Z) and energy (E) (HZE) nuclei. GCR exposure rate increases about three times as spacecraft venture out of Earth orbit into deep space where protection of the Earth's magnetosphere and solid body are lost. NASA's radiation standard limits astronaut exposures to a 3% risk of exposure induced death (REID) at the upper 95% confidence interval (CI) of the risk estimate. Fatal cancer risk has been considered the dominant risk for GCR, however recent epidemiological analysis of radiation risks for circulatory diseases allow for predictions of REID for circulatory diseases to be included with cancer risk predictions for space missions. Using NASA's models of risks and uncertainties, we predicted that central estimates for radiation induced mortality and morbidity could exceed 5% and 10% with upper 95% CI near 10% and 20%, respectively for a Mars mission. Additional risks to the central nervous system (CNS) and qualitative differences in the biological effects of GCR compared to terrestrial radiation may significantly increase these estimates, and will require new knowledge to evaluate.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Astronauts*
  • Cosmic Radiation*
  • Earth, Planet
  • Humans
  • Mars
  • Models, Statistical*
  • Occupational Exposure*
  • Protons*
  • Radiation Dosage
  • Radiation Protection
  • Risk Assessment
  • Space Flight / ethics*
  • Spacecraft


  • Protons

Grant support

This work was supported by the NASA Space Radiation Risk Project, and the University of Nevada Las Vegas. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.