Born in Los Angeles, California, on 1928 April 28, Eugene Merle Shoemaker graduated from the California Institute of Technology in Pasadena at the age of 19. A thesis on the petrology of Precambrian metamorphic rocks earned him a master's degree only a year later, at which point he joined the United States Geological Survey, an organization with which he remained at least partly associated for the rest of his life. His first work for the USGS involved searching for uranium deposits in Colorado and Utah. While doing this, he also became interested in the moon, the possibility of traveling there, and of establishing the relative roles of asteroidal impacts and volcanic eruptions in forming the lunar craters. He then embarked on work for a Ph.D. at Princeton University, intending to continue his study of metamorphic petrology, although this was interrupted when the USGS again sent him to the field, this time leading him to an investigation of volcanic processes, for it was in the eroded vents of ancient volcanoes that the uranium deposits were often located.
Gene Shoemaker and Carolyn Spellman were married in 1951. A visit to Arizona's Meteor Crater the following year began to set Gene toward the view that both it and the lunar craters were due to asteroidal impacts. In 1956 he tried to interest the USGS in the construction of a geological map of the moon. This work was sidelined, because the national interest in the production of plutonium led him to study of the craters formed in small nuclear explosions under the Yucca Flats in Nevada and invited a comparison with Meteor Crater. It was then that he did his seminal research on the mechanics of meteorite impacts that included the discovery, with Edward Chao, of coesite, a type of silica produced in a violent impact. Awarded a master's degree in 1954, Gene Shoemaker received his doctorate from Princeton in 1960 with a thesis on Meteor Crater.
In 1961 he took a leading role in the USGS venture, in Flagstaff, Arizona, into the study of "astrogeology", the Ranger missions to the moon and the training of the astronauts. It had long been Gene's dream to go to the moon himself, but in 1963 he was diagnosed as having Addison's disease, a condition that prevented him from becoming an astronaut. When the USGS Center of Astrogeology was founded in Flagstaff in 1965, he was appointed its chief scientist and organized the geological activities planned for the lunar landings. In 1969 he returned to Caltech as a professor of geology and served for three years as chairman of the Division of Geological and Planetary Sciences there. Until he retired from the professorship in 1985 he divided his time between Pasadena and Flagstaff. He continued to maintain an office in the USGS Astrogeology building after his formal retirement in 1993, while at the same time taking up a position at the Lowell Observatory.
It was shortly after the 1969 arrival in Pasadena that he became interested in extending his geological knowledge of the formation and distribution of terrestrial and lunar impact craters to the study of the astronomical objects that formed them. With Eleanor Helin he developed a plan to search for such objects --the Apollo asteroids-- with the 0.46-m Schmidt telescope at Palomar. This search program had its first success in July 1973 and was soon, with the help also of a number of students and of collaborations using other Schmidt telescopes, significantly augmenting the rather meager knowledge that had been accrued on these objects during the previous four decades.
Carolyn became involved with measuring images from the Palomar films in 1980, and in 1982 the Helin and the Shoemaker observing programs with the 0.46-m Schmidt went their separate ways. Carolyn proved to be very adept at scanning the Schmidt films, and this new phase of the search program had its first success with the discovery of (3199) Nefertiti, an Amor asteroid with its perihelion 0.13 astronomical unit outside the earth's orbit. In 1983 the first of the record 32 comets associated with the Shoemaker name was discovered. By the time the observing program ended, in late 1994, it had produced 40 of the --now-- 417 known Amor, Apollo and Aten asteroids (the orbits of this last group being smaller than that of the earth). Together with the other observing programs at Palomar, the Shoemakers have ensured that Palomar recently became and is likely to remain the leading site for the discovery of asteroids, with currently more than 13 percent of asteroids that have been numbered having been found there. A few months before the Shoemaker program was terminated came its "defining moment", with Gene receiving the thrill of his lifetime when some 20 components of one of those 32 comets were observed to crash into the planet Jupiter with astoundingly dramatic results.
Carolyn also went along on Gene's annual trips to Australia to examine impact craters, and the tragic irony that his own death should occur there as the instantaneous result of another violent impact would not have been lost on him. Gene lived as he died, active to the hilt, his enquiring mind participating in the adventure of ever learning more over an unusually large range of scientific disciplines. His many honors included the Wetherill Medal of the Franklin Institute in 1965, election to membership in the National Academy of Sciences in 1980, the Gilbert Award of the Geological Society of America in 1983 and the Kuiper Prize of the American Astronomical Society in 1984. Above all, he was truly the "father" of the science of near-earth objects, to the discovery and study of which The Spaceguard Foundation is dedicated, and his expertise and drive will be sorely missed.
Brian G. Marsden