UC Berkeley

This project has examined one specific issue facing human explorers at Mars - radiation dose from solar particle events (SPEs). While the issue is specific, the work involved in carrying out this study has been truly multidisciplinary. From space physics to modeling the Martian atmosphere to assessing radiation risk to humans, a lot of ground is covered. At each point along the way, efforts were made to clarify the science and assumptions used to derive quantitative estimates and draw meaningful conclusions. The data and analyses provided in this project represent the most comprehensive study of SPE's at a planetary body other than Earth. The analysis includes dose estimates from galactic cosmic radiation.

The specific aims of this project are to:

1. Establish a methodology for estimating the fluence of energetic particles at Mars from SPEs;

2. Establish a predictive model to estimate the frequency of SPE occurrence and cumulative SPE fluence received at Mars, as a function of the Solar Cycle;

3. Develop a model to estimate the fluence of energetic particles from SPEs on the Martian surface;

4. Estimate and assess the radiation dose on the Martian surface from SPEs, as compared to galactic cosmic radiation (GCR); and

5. Assess the viability of various types of shielding and mission profiles to mitigate the radiation risk to human explorers on the Martian surface.

Some of the conclusions drawn from this study include:

* The MCP detector onboard MGS ER (and presumably other spacecraft) can serve as an effective detector for high-energy ionizing radiation.

* Though more work is necessary, it is possible to estimate future solar activity at Earth and Mars based on current solar observations.

* Spectral information from SPE's at Mars is required to thoroughly assess the radiation environment on the Martian surface.

* An unshielded astronaut on the Martian surface may face long-term and acute radiation risk from SPE's, depending on the likelihood of their occurrence.

* Various mitigation strategies can be employed to minimize the radiation risk to human explorers on Mars, though shielding is limited for astronauts outside of a fixed habitat.