Only three and a half years passed between the first moon landing in 1969 and the sixth and last moon landing in 1972. But while the first landing was an enormous achievement in itself, the last landing contributed far more to the advancement of scientific knowledge. On the first mission, the two astronauts were on the Moon for only a few hours and remained close to the landing site. Their time on the Moon was just sufficient to conduct several experiments and collect a small sample of lunar rocks. On the last mission, however, the three men (one of whom was a geologist) spent much more time on the lunar surface—three periods of about seven hours. With their special moon vehicle, they could travel much further from the landing site to investigate more of the lunar environment and collect a wider range of soil and rock samples.