We have met the space aliens … and they are us, according to one of the last two men to set foot on the moon, 30 years ago. “I was an alien on the moon,” Harrison “Jack” Schmitt told 200 students Tuesday at Malcolm S. Mackay Elementary School. “So was Gene Cernan,” said Schmitt, who walked on the lunar surface with Eugene Cernan, commander of Apollo 17. Earthlings are aliens when they visit other worlds, he told a student who asked him whether space aliens were real. “Some of you may want to go to Mars and maybe raise your families there,” Schmitt told the second- through fifth-graders. “If you have a child on Mars, that child will be -what? -a Martian!”