Apollo 17 investigate the possibility of relatively new volcanic activity in the same area. Cernan, Evans, and Schmitt returned to Earth on December 19 after a 12-day mission. Apollo 17 is the most recent manned Moon landing and the most recent time humans travelled beyond low Earth orbit. It was also the first mission to have no one on board who had been a test pilot; X-15 test pilot Joe Engle lost the lunar module pilot assignment to Schmitt, a geologist. The mission broke several records: the longest moon landing, longest total extravehicular activities (moonwalks), largest lunar sample, and longest time in
Far side of the Moon 17 missions since that time, and photographed by multiple lunar probes. Spacecraft passing behind the Moon were out of direct radio communication with the Earth, and had to wait until the orbit allowed transmission. During the Apollo missions, the main engine of the Service Module was fired when the vessel was behind the Moon, producing some tense moments in Mission Control before the craft reappeared. Geologist-astronaut Harrison Schmitt, who became the last to step onto the Moon, had aggressively lobbied for his landing site to be on the far side of the Moon, targeting the lava-filled crater Tsiolkovskiy. Schmitt's ambitious