Named in honor of Luis W. Alvarez {1911–1988}, physicist and Nobel laureate, and his son Walter Alvarez, geologist, both on the faculty of the University of California at Berkeley. The Alvarezes headed a team that discovered a global geochemical anomaly of noble metals at the Cretaceous-Tertiary boundary. They propounded the theory that a mass extinction of living species at the end of the Cretaceous period was triggered by impact of an asteroid or a comet about 10 km in diameter. Their work has stimulated intensive international research on the possible relationships between large body impacts and the evolution of life. (M 12807) _ _.