Mars Mission Radiation Dose/Shielding Summary Note: Dr. Cary Zeitlin generously contributed these slides from two full-length presentations. For brevity’s sake, supporting details have been removed. Use at your own risk… Contributor Credits: Cary Zeitlin (SwRI), NASA, Lawrence Berkeley National Lab Collator: Brian Enke (SwRI)

Dose Dose is physical: energy deposited per unit mass. 1 gray = 1 Gy = 1 J / kg = 100 rads

Dose equivalent 1 sievert = 1 Sv = 100 rem. Sv dffers from Gy by weighting factor: – w R = 1 for sparsely-ionizing types, e.g.,  – w R = 5 for protons, 20 for  and heavier nuclei. In “mixed field” w R replaced by Q(L).

Shielding against GCR is impractical. Some exposure to heavy ions is inevitable in space. DNA repair works for simple damage, but heavy ions cause complex damage.

15 th Humans in Space, Graz, Austria

1% 0.1%.01% Maximum Acceptable Risk = 3% Shuttle Mission ISS Mission Mars Mission Increase in Individual’s Risk of Fatal Cancer ▲ ▲ ▲ “95% Confidence Interval” 10 % Lunar ▲ SPE??

15 th Humans in Space, Graz, Austria Dose Reduction Chart Revisited Hydrogen clearly superior as predicted by Wilson et al. Best-performing composites give results similar to CH 2.

Conclusions from ODY GCR ~ as expected from models & near-Earth data. Radial gradient for solar particles is large  SPE weaken as they propagate out to Mars. Need ground truth – surface environment more complex.

GCR transport model calculation from NASA-JSC. Unshielded doses ~ 1000 times greater on Mars than Earth but lower than free space by factor of 2. Surface well-shielded from most SPEs. Annual dose-equivalent (Sv/yr)

Mars Science Laboratory Next Mars rover Launches Nov Includes RAD, a small (1.5 kg) but capable detector with neutron capability.