It's not cost effective. (Same reason we don't encase it in giant synthetic diamonds or bury it in the earth's mantle) Plus the material is valuable & space la

It's not cost effective. (Same reason we don't encase it in giant synthetic diamonds or bury it in the earth's mantle) Plus the material is valuable & space launches are dangerous. Launching to space probably introduces more contamination risk than any other option short of intentionally making dirty bombs out of it