Harrison Schmitt credits the image to the entire Apollo 17 crew. While on the Moon's surface, Schmitt — the only geologist in the astronaut corps — collected the rock sample designated Troctolite 76535, which has been called "without doubt the most interesting sample returned from the Moon". Among other distinctions, it is the central piece of evidence suggesting that the Moon once possessed an active magnetic field. As he returned to the Lunar Module before Cernan, Schmitt is the next-to-last person to have walked on the Moon's surface. After the completion of Apollo 17, Schmitt played an active role in documenting the
United States Astronaut Hall of Fame Seven. In addition to being the first American astronauts, they set several firsts in American spaceflight, both auspicious and tragic. Alan Shepard was the first American in space and later became one of the twelve people to walk on the Moon. John Glenn was the first American to orbit the Earth and after his induction went on, in 1998, to become the oldest man to fly in space, aged 77. Gus Grissom was the first American to fly in space twice and was the commander of the ill-fated Apollo 1, which resulted in the first astronaut deaths directly related to