Why haven’t humans been back to the moon in over 50 years?

By Jacopo Prisco, Jackie Wattles, CNN (CNN) — As he took his final steps before leaving the moon, Apollo 17 commander Gene Cernan had some poignant closing words: “We leave as we came, and, God willing, as we shall return, with peace and hope for all mankind.” It was December 14, 1972, and Cernan knew