Green fireballs are a type of unidentified flying object (UFO) that people have seen since the early 1950s. These sightings mostly happened in the southwestern United States, especially in New Mexico. Some researchers and groups that study UFOs believe green fireballs might come from space, but other explanations say they are natural bolides.

Reports and responses

Early reports of green fireballs began in late 1948 in New Mexico. On the night of December 5, 1948, two plane crews—one civilian and one military—saw bright green fireballs in the sky. They described the objects as a "green ball of fire" and "like a huge green meteor." On December 8, two pilots reported another sighting of a green fireball from the air.

On December 20, 1948, Lincoln LaPaz, an astronomer from the University of New Mexico, wrote a letter to the U.S. Air Force (as noted by ufologist Kevin Randle) stating that the objects were unusual for meteors. On January 13, 1949, the Director of Army Intelligence from Fourth Army Headquarters in Texas suggested that the green fireballs "may be the result of radiological warfare experiments by a foreign power." He also said the sightings were important because they occurred near sensitive military locations and recommended a scientific group study the events.

In February 1949, a meeting at Los Alamos attended by members of Project Sign, scientists like Joseph Kaplan and Edward Teller, and military personnel could not explain the origin of the green fireballs. Later that year, secret meetings about the fireballs were held at Los Alamos and other locations, as reported by Edward Ruppelt and ufologists like Jerome Clark. In December 1949, Project Twinkle, a system for observing and photographing green fireballs, was created but was never fully used. It was stopped two years later, with the official conclusion that the events were likely natural.

In May 1949, Donald Menzel, a theoretical astrophysicist and UFO skeptic, saw a green fireball near Alamogordo. He later said it was probably a normal meteor. More recently, green fireballs have been seen in Japan, Australia, West Virginia, and Tennessee.

Explanations

Some scientists who study UFOs believe green fireballs may have a man-made or extraterrestrial origin. Other scientific explanations, aside from meteors or bolides, include effects from atomic bomb tests, such as nuclear fallout, material from the Moon caused by meteor impacts, and aircraft linked to secret military programs.