and left NASA with nothing to do...
Nick -
What I love about Mars is not only that it lacks much of a magnetosphere, and thus does not have much protection against any particle stream, but in addition Mars also has a gravity field to pull stray particles (radiation) towards it.
Isotopes will pool toward the surface. Why do you think Hellas has so much "water"?
Nor do the neutrons simply disappear - instead, they lie near Mars' surface, waiting for interaction with other particles to raise their energy state, and then interact with other substances - including organics.
Mars is radioactive. Talk to someone is your physics department.
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