UAP · 2026-07-10

1949 Los Alamos "Green Fireballs" — The Manhattan Project Scientists' UAP Investigation, Now in PURSUE

Of all the historical documents in PURSUE Release 04, the most significant may be the shortest to describe: a 1949 conference record covering the wave of "green fireball" sightings observed near Los Alamos National Laboratory in 1948–1949. Conference attendees included prominent scientists who had worked on the Manhattan Project. The event pre-dates the U.S. Air Force's Project Blue Book by several years.

Los Alamos "Green Fireballs" Conference, 1949

Cold War-era investigation of an unexplained aerial phenomenon over Los Alamos National Laboratory. Attendees: Manhattan Project scientists. Source: war.gov/UFO.

What the green fireballs were

Beginning in late 1948 and continuing through 1949, observers around Los Alamos National Laboratory, Sandia National Laboratories, and the wider American Southwest reported bright green fireballs streaking across the night sky. The lights moved at velocities and altitudes inconsistent with then-known meteor or aircraft profiles. Because the sightings clustered around the sites of the most sensitive U.S. nuclear-weapons work, they were treated with unusual seriousness — not as a public-interest UFO story, but as a possible national-security question.

Why this file matters: The green-fireballs episode is one of the earliest documented cases of the U.S. government convening working scientists — including atomic-era luminaries — to formally investigate an aerial phenomenon they could not explain. Its inclusion in PURSUE Release 4 pulls the archive's start date back to 1948–1949 and links the modern-era program to the Cold War's founding moments.

The scientists who attended

Historical accounts of the 1949 Los Alamos conference on green fireballs list attendees drawn from the Los Alamos and Sandia laboratories, with additional participation from the U.S. Air Force. Some of the scientists present had worked on the Manhattan Project during World War II. The astronomer Dr. Lincoln La Paz — who studied and named the phenomenon — figures prominently in the historical record but the specific attendee list in the PURSUE PDF release will be canonicalised as the document is analysed.

What the conference concluded

The 1949 conference did not conclusively identify the green fireballs. Investigators considered natural (bolide, atmospheric plasma) and technological (foreign reconnaissance, secret U.S. test) origins. The green fireballs were also examined by Project Twinkle, a formal Air Force investigation established in 1949 specifically to instrument-monitor them. Twinkle ended in 1951 with the phenomenon still unresolved.

Where this file sits in the PURSUE Cold War thread

Together with the R03 CIA-UAP-002 Scientific Advisory Panel on Unidentified Flying Objects (the Robertson Panel, 1952–53), the R03 US Navy Report of Flying Discs (1948), and the R04 Project Sign document (1948), the Los Alamos green-fireballs record forms a coherent picture of the 1948–1953 Cold War-era U.S. institutional response to unexplained aerial phenomena. All four documents are now public.

Browse every PURSUE fileOpen UAP files

For Release 04's full inventory, see the SkyLens overview. The original PDF is on war.gov/ufo.

Official PURSUE Release 04 record · U.S. Department of War · published July 10, 2026 on war.gov/UFO