Democratic Senate candidate Bill Nelson said Tuesday if Florida voters send him to Washington, D.C., he will make a manned mission to Mars among his legislative priorities. “In my lifetime, what I want to see is a mission from planet Earth to planet Mars with an international crew that returns safely,” said Nelson, 57, who is at the Democratic convention promoting his candidacy. “I think we can do that. We have the technology. We just have to have the will to do.”