For his Ph.D. at Princeton, Dr. Shoemaker conclusively showed that Barringer Meteor Crater arose from meteor impact.
Dr. Shoemaker founded the Astrogeology Research Program of the USGS in 1961 and was its first director. He was prominently involved in the Lunar Ranger missions to the Moon, which showed that the Moon was covered with a wide size range of impact craters. Dr. Shoemaker was also involved in the training of the American astronauts.
Coming to Caltech in 1969, he started a systematic search for Earth-crossing asteroids, which resulted in the discovery of several families of such asteroids, including the Apollo asteroids.
Dr. Shoemaker received a National Medal of Science in 1992. In 1993, he co-discovered Comet Shoemaker-Levy 9, which was the first observed planetary impact of a comet.
Dr. Shoemaker perished in a car crash in Alice Springs, Australia in 1997. His ashes were carried to the Moon by the Lunar Prospector space probe.