Humans haven’t set foot on the Moon — or any other world outside of our own, for that matter — since Cernan and Schmitt departed the lunar surface on December 14, 1972. That will make 40 years on that date this coming December. And despite dreams of moon bases and lunar colonies, there hasn’t even been a controlled landing there since the Soviet Luna 24 sample return mission in 1976 (not including impacted probes.) So in light of the challenges and costs of such an endeavor, is there any real value in a return to the Moon? Even though some research on the lunar surface may be able to be performed by robotic missions, [these scientists] believe that “addressing them satisfactorily will require an end to the 40-year hiatus of lunar surface exploration.” Read more: Is It Time to Return to the Moon?