Leon T. “Lee” Silver, 1925–2022

Leon T. SilverLeon Theodore “Lee” Silver, an American geologist who was an emeritus professor at the California Institute of Technology (Caltech), passed away on January 31, 2022. He was 96 years old.

Silver was an instructor to the Apollo 13, 15, 16, and 17 astronaut crews. Working with NASA, he taught astronauts how to perform field geology, essentially creating lunar field geology as a new discipline. His training is credited with a significant improvement in the J-Mission Apollo flights’ scientific returns. After the Apollo program, he became a member of the U.S. National Academy of Sciences in 1974. He retired as the W. M. Keck Foundation Professor for Resource Geology, emeritus, at Caltech.

Silver was born in Monticello, New York, on April 9, 1925. His father and mother emigrated from Russia and Poland, respectively, and met in Brooklyn. Silver graduated from high school in 1942, just months after the U.S. entered World War II. He joined the Navy Reserve while studying at the Colorado School of Mines and was called up to active service in 1943, having turned 18 only three months earlier.

Through the V-12 Navy College Training Program, which paid the college tuition of engineering students who were expected to become officers at the end of their studies, Silver earned a bachelor’s degree from the University of Colorado in 1945. He served in the Navy until 1946, then earned a master’s degree from the University of New Mexico in 1948 and a doctorate in geology and geochemistry from Caltech in 1955. During this time, he also worked at the U.S. Geological Survey (USGS).

After completing his doctoral degree, Silver began teaching at Caltech as an assistant professor of geology in 1955. He was promoted to associate professor in 1962 and earned tenure in 1965. He was named the W. M. Keck Foundation Professor for Resource Geology in 1983 and became emeritus in 1996.

Silver’s main research interests were petrology, tectonics, and applications of geology and isotope geochemistry to geochronology, crustal evolution, ore deposits, and comparative planetology. He is perhaps most famous for his contributions to the Apollo program during the 1970s. He instructed Apollo astronauts on geology and lunar sample selection — including Apollo 17 astronaut and Caltech alumnus Harrison “Jack” Schmitt — and developed approaches for using isotope ratios for geochronology, the study of the age and history of rocks and sediments. In addition to his instruction of the astronauts, Silver served on the Lunar Surface Geology Experiment Team (Apollo 13–17), the Lunar Sample Preliminary Examination Team (Apollo 15–17), the Lunar Surface Traverse Planning Team (Apollo 15–17), the Lunar Science Working Panel (Apollo 15–17), and the Lunar Sample Analysis Planning Team (1972–1974).

Silver’s work with the Apollo program has been recounted in Andrew Chaikin’s A Man on the Moon (1994). The book became a TV mini-series in 1998, with David Clennon portraying Professor Silver in the HBO docudrama series From The Earth To The Moon. In 2006, Apollo 15 Commander Dave Scott devoted a section of his co-authored book Two Sides of the Moon to the training and instruction that Scott and other Apollo astronauts received from Silver.

Silver also served on several federal advisory committees, including as chair of the Advisory Committee to the Office of Basic Energy Sciences of the Department of Energy from 1990 to 1992. Throughout his career, he received numerous honors and awards, including a NASA Exceptional Scientific Achievement Medal both for his training of the Apollo astronauts in geologic science and for his individual research. He was also selected to receive a Guggenheim Fellowship, an American Institute of Professional Geologists Award for Professional Excellence, and numerous NASA Group Achievement Awards. He was named a member of the National Academy of Sciences and a senior fellow of the Mineralogical Society of America and served as president of the Geological Society of America in 1979.

In 2002, Silver was the subject of an interview with the NASA Johnson Space Center Oral History Project. To read the transcript of that interview, visit https://tinyurl.com/bjydzsru.

— Portions of text courtesy of the California Institute of Technology