Twice every year, the FBI assembles the National Mission Force for Marble Challenge, a complex inter-agency test of the ability of the blackest parts of the federal government to find and “render safe” a ticking nuclear bomb. It is the domestic counterpart exercise to Vital Archer I wrote about yesterday that takes place in Canada, and a drill that has become more and more sophisticated over the years, folding in not just conventional and unconventional military assets but also scientists from the Department of Energy, the Environmental Protection Agency, and the Centers for Disease Control and Prevention.