Green Fireballs — Los Alamos Nuclear Sites 1948–51

Beginning in December 1948, a wave of brilliant green-colored fireballs began appearing over the most sensitive nuclear installations in the United States — Los Alamos National Laboratory, Sandia National Laboratories, Kirtland Air Force Base, and White Sands Missile Range. The fireballs were characterized by an unusually flat trajectory inconsistent with meteors, a distinctive artificial-looking green color, and the ability to maintain level flight. Dr. Lincoln LaPaz, one of the world's foremost authorities on meteorites and meteors and a consultant to the US government, investigated multiple events and formally concluded that the green fireballs were not meteors or any known natural phenomenon. The objects appeared to be intelligently controlled. The Air Force Director of Intelligence ordered a formal classified investigation. In 1949, Project Twinkle was established — a classified monitoring project deploying cinetheodolite tracking cameras at multiple New Mexico sites to capture the phenomena. The green fireball events continued through 1951. Despite Project Twinkle's instrumented monitoring program, definitive photographic tracking data was not obtained. The concentration of anomalous aerial phenomena specifically over US nuclear weapons research and development sites — during the period of the US nuclear monopoly — was regarded by investigators including LaPaz as potentially indicating surveillance of nuclear capabilities by an unknown intelligence. The green fireball wave was one of the direct predecessors of the Wave of 1952 and contributed significantly to the institutional pressure to create formal UAP investigation programs.