What happened
From late 1948 a run of brilliant green lights crossed the night skies of New Mexico, close to the most secret atomic sites in the country. On 5 December 1948 two aircrews, one civilian and one military, reported a green ball of fire, and more reports followed from pilots, security staff and federal agents. University of New Mexico meteor specialist Lincoln LaPaz, who saw one himself on 12 December, told the Air Force they did not act like meteors: they shone at constant brightness, flew nearly level eight to ten miles up and made no sound. A fireball on 30 January 1949 was watched by more than 100 people across New Mexico and West Texas. In February 1949 Los Alamos hosted a secret conference with Edward Teller, Norris Bradbury, Joseph Kaplan and LaPaz. PURSUE has since published two central records: an Armed Forces Special Weapons Project file on 209 sightings of green orbs, discs and fireballs near Sandia Base from 1948 to 1950 (DOW-UAP-D017, Release 02) and the transcript of the 1949 Los Alamos conference (DOE-UAP-D004, Release 04).
The official explanation
The Air Force set up Project Twinkle in December 1949 to photograph and triangulate the fireballs. It was never fully put into operation and was closed about two years later with the conclusion that the lights were probably natural. Many astronomers have treated them as unusually bright bolides whose green colour comes from metals such as magnesium or nickel, and Donald Menzel came to regard a green fireball he saw near Alamogordo in May 1949 as an ordinary meteor. Other proposals recorded on Wikipedia include after-effects of atomic tests, lunar material knocked loose by impacts, and secret military projects.
The anomalous case
The people best qualified to judge thought this was not ordinary. LaPaz, a leading meteor expert, said the 12 December 1948 fireball was certainly not a normal meteorite fall, and Newsweek's reading of the newly released transcript shows him calling the objects' silence their most implausible feature. They held steady brightness, flew nearly level at constant speed, and clustered around Los Alamos and Sandia, the core of the US nuclear program. In January 1949 Army intelligence even raised the possibility of foreign radiological warfare experiments and urged a scientific study. The transcript shows the physicists could not match the phenomenon to any natural cause, and the Sandia file logs more than 200 sightings around a single weapons base. Researcher Joshua Golembeske, quoted by Newsweek, sees the green fireballs as an early chapter in a recurring link between UAP and nuclear facilities.
The strongest argument that this was something genuinely unknown or classified, with each claim attributed to the person who made it.
Documents
- PURSUE Release 02 (22 May 2026), WAR.GOV/UFO official, war.gov
- DOW-UAP-D017: UAP Reported at Sandia Base, 1948-1950 (Armed Forces Special Weapons Project) (PURSUE Release 02) official, war.gov
- PURSUE Release 04 (10 July 2026), WAR.GOV/UFO official, war.gov
- DOE-UAP-D004: Los Alamos Conference on Aerial Phenomena, 1949 (PURSUE Release 04) official, war.gov
Sources
- UFO files: the 1949 Los Alamos green fireball mystery declassified Newsweek
- Green fireballs Wikipedia
- Pentagon releases fourth batch of UFO files CBS News
- 2nd batch of Pentagon UAP files: over 50 videos to watch EarthSky
- Pentagon adds 40 UAP files to public archive MyChesCo
Witness reports elsewhere
These archives can't be republished here, so we link to them instead.