On Dec. 14, 1972, a capsule carrying Apollo 17 astronauts Eugene Cernan and Harrison Schmitt lifted off from the lunar surface.
It was the day that humans left the moon.
For a long while, they didn't come back, but that's changing. China, India and even smaller nations like Israel and South Korea are all pursuing robotic moon missions. Their lunar ambitions are being driven both by a desire to flex their technological muscles and by the rise of global nationalism.