Leon Silver

Leon Theodore Silver (April 9, 1925 – January 31, 2022) was an American geologist. He was professor of geology at the California Institute of Technology (Caltech). He was an instructor to the Apollo 13, 15, 16, and 17 astronaut crews. He taught astronauts how to perform field geology and created lunar field geology.
He became a member of the United States National Academy of Sciences in 1974. 
Silver died on January 31, 2022 in Arcadia, California, at the age of 96.