1. The Number and Reaction Multiplicities of GCR Nuclei and Delta-rays Passing through a Cell Nucleus on a Mars Mission Xiaodong Hu 1, Premkumar Saganti 2, Francis A. Cucinotta 3, 1 U.S.R.A., Houston TX, 2 Lockheed Martin, Houston TX and 3 NASA Lyndon Johnson Space Center Houston TX, 77058.

2. Fig. 1. Results of calculations of the integral number of particle tracks per cell per Year from GCR exposures in free space at solar minimum as a function of ion charge Behind 5 g/cm 2 Aluminum using cell areas of 100 um 2, the upper curve is with Delta- rays and lower curve is without Delta-rays.

3. Multiplicities of GCR Reaction Events Nuclear reactions produced by GCR as they traverse tissue are quite frequent. Reaction lead to high-multiplicity events with a large number of ions produced in a small volume (<1 cm) The reaction products are distributed between –Target like (highly ionizing from tissue constituents) –Projectile like including projectile fragment and like particles –Intermediate rapidity fragments For Biological damage, the highly ionizing target fragments are most important and can lead to a high doses in small volumes (>1 Gy) The Quantum multiple scattering model of nuclear fragmentation (QMSFRG) is used to model multiplicities and combined with the HZETRN code to project the number and types of high-multiplicity events in tissue from GCR.

4. La + La Collision showing high multiplicity event

5. Fig. 2a. The probability of a nuclear reaction per cm of tissue traversed versus energy for several ions prominent in the GCR.

6. Fig. 2b. Comparisons of the elemental fluence of GCR ions near solar minimum to the number of nuclear interactions that occur per cm of tissue traversed by each charge GCR group. Calculations are made behind 5 cm of tissue.