This point drifted past me last time but I have now nailed it securely:-

You are totally and stupidly wrong about C14:

Carbon 14 is produced, on earth, by the interaction of cosmic rays with the NITROGEN in the atmosphere (70%). This interaction takes place at a range of altitudes, but typically at quite high altitude, as the cosmic ray passes through enough atmosphere to be "assured" of a hit.

On Mars:-

1) There is very little nitrogen in the atmosphere (2.7%)
2) The atmosphere is thin enough that many (most) of the cosmic rays penetrate to the ground without interacting with the atmosphere.
3) There is very little (essentially none) Nitrogen in the regolith.

As a consequence, C14 is expected to be exceedingly rare on Mars.

As a first approximation, the amount of C14 is expected to occur in the ratio of Nitrogen abundances times the ratio of atmospheric pressures i.e. 2.7/70*0.007 = 0.00027! Since the ratio of C14 on earth is already 1 in 10^12, we are looking at a very small number and a trivial radiation load from C14 decay,

QED

There will be other elemental transmutations under this rain of cosmic rays, some of which will be more common on Mars than Earth. in this category, I would expect a number of short-lived and a few stable isotopes of medium mass molecules heavier than carbon.

There might well be more C13 and less C12 than on Earth, due to neutron capture, but the detailed physics is important, and I'm not sufficiently well-grounded to be sure what will and what won't be produced, other than being very confident that due to lack of nitrogen, there will very little C14!