The thyroid is one of your most sensitive organs when it comes to radiation. Radiation on mars is especially high so you are at greater risk for cancer and mutation in genes. If there is a mutation in a gene, it can be passed down to the next generation. The average neck diameter for a woman is 4 inches. The average for a male is 6 inches. Although I didn’t find that lead is printable; I do feel as though it can be printed in the future.Scientists have come up with BNNTs which can be woven into their space suits so they can have even more protection to all of their organs. Also I would recommend taking KI, which is potassium iodide, to protect your thyroid. There are more things that they could bring with them to Mars like prussian blue; (type of dye) this speeds up the elimination of the radioactive particles, and diethylenetriamine pentaacetic acid (DTPA) which helps reduce the amount of radiation your body takes in. All of these things will help with radiation in space.