Harrison Schmitt cancelled in September 1970, the community of lunar geologists supporting Apollo felt so strongly about the need to land a professional geologist on the Moon, that they pressured NASA to reassign Schmitt to a remaining flight. As a result, Schmitt was assigned in August 1971 to fly on the last mission, Apollo 17, replacing Joe Engle as Lunar Module Pilot. Schmitt landed on the Moon with commander Gene Cernan in December 1972. Schmitt claims to have taken the photograph of the Earth known as "The Blue Marble", possibly one of the most widely distributed photographic images in existence. NASA officially
NASA Astronaut Group 4 natural sciences or engineering was a prerequisite for selection), with NASA providing pilot training as necessary. Initial screening of applicants was conducted by the National Academy of Sciences, which characterized the pool as "disappointing." Of the six ultimately chosen, four had military experience, with Garriott having previously completed the USAF Pilot Training Program. Schmitt, a geologist, walked on the Moon, while Garriott, Gibson and Kerwin all flew to Skylab. Garriott also flew on the Space Shuttle. Graveline and Michel left NASA without flying in space. NASA Astronaut Group 4 Astronaut Group 4 (The Scientists) was a group of six astronauts