Harrison Schmitt

Dr. Harrison "Jack" Schmitt, 74, was the 12th of the 12 moonwalkers and the only geologist and scientist to walk on the Moon. He flew in space as part of the Apollo 17 crew that explored the Moon in December 1972.

He later became the only Apollo moonwalker to be elected to the United States Senate and the only natural scientist to serve there since Thomas Jefferson.

Dr. Schmitt stopped signing autographs in 2002.