Los Alamos Conference on Aerial Phenomena, March 22, 1949 — Department of Energy File
This document is a transcript of a 1949 conference held at Los Alamos Scientific Laboratory (now Los Alamos National Laboratory), Los Alamos, New Mexico. Attendees included several eminent scientists and physicists, many of whom had contributed to the development of the first nuclear weapons…
Incident Overview
On March 22, 1949, in New Mexico, the Department of Energy preserved a documentary record that was declassified and published on July 10, 2026 as part of the fourth tranche of the Department of War’s Presidential Unsealing and Reporting System for UAP Encounters (PURSUE).
The date carried on the file is that of the Atomic Energy Commission’s classified transmittal, the covering letter under which the transcript was circulated; the meeting it records had convened some weeks earlier, in February 1949, in a conference room at the Los Alamos Scientific Laboratory. The men who sat down at that table had, four years previously, built the atomic bomb. They were assembled to answer a question that would sound absurd in almost any other setting, and which in this one was a matter of national security: what were the green fireballs, and why were they appearing over the most sensitive ground in the United States?
What the government released
This document is a transcript of a 1949 conference held at Los Alamos Scientific Laboratory (now Los Alamos National Laboratory), Los Alamos, New Mexico. Attendees included several eminent scientists and physicists, many of whom had contributed to the development of the first nuclear weapons during the Manhattan Project. The purpose of the conference was to discuss and gather hypotheses to account for the nature and origin of a phenomenon involving “green fireballs” that had been reported over a period of several months in the vicinity of the laboratory. The group did not come to a consensus on a likely attribution for the phenomenon, though a leading hypothesis was that the observations may have been related to meteors entering the atmosphere at a shallow angle and high altitude. Dr. Edward Teller suggested that if not a “material body,” an “electron phenomenon” might be the cause, while Dr. Lincoln LaPaz, an expert specializing in meteorics, expressed that “nothing like this, to [his] knowledge, has ever been observed in the case of meteorite drops.”
The historical record
The wave began in earnest on the night of 5 December 1948, when two separate aircrews over New Mexico — one military, one civilian — reported a green ball of fire crossing their path. Through that December the sightings came almost nightly, and they continued into 1949. Witnesses described a hard, distinctly green light, brighter than any star, travelling on a flat and nearly horizontal course and extinguishing without the lingering trail a bright meteor ordinarily leaves. What made this a security problem rather than an astronomical curiosity was where the reports clustered: over the Los Alamos laboratory, over Sandia Base at Albuquerque where nuclear weapons were assembled and stored, and over the airfields strung across the same desert. Something was moving over the American nuclear complex, and nobody could say what.
The disagreement preserved in this transcript is what gives the document its weight. Dr. Lincoln LaPaz, who directed the Institute of Meteoritics at the University of New Mexico, was the most qualified man in the country to call the fireballs meteors — and he would not. He had plotted their trajectories, canvassed witnesses, and walked the ground beneath the calculated fall lines, and had recovered nothing: no fragments, no craters, no scorched earth. The colour was wrong, the paths too level, the debris absent. Edward Teller, the Hungarian-born physicist later saddled with the title of father of the hydrogen bomb, approached the same evidence from the other end and reached for a non-material explanation. The meeting broke up with the shallow-angle meteor hypothesis leading on points and no one entirely persuaded, including, by the plain sense of the transcript, the men advancing it.
That absence of consensus is not a hidden conclusion waiting to be decoded. It is the conclusion. The Air Force went on to mount Project Twinkle, a programme of instrumented observation posts in New Mexico meant to photograph and triangulate the fireballs; it was under-resourced, it caught little, and it was wound up in the early 1950s with the phenomena judged probably natural. LaPaz himself, the great sceptic of the meteor theory, never argued for visitors from elsewhere — his suspicion ran to secret devices, American or Soviet. The broad shape of this meeting has been known to researchers for decades through Freedom of Information Act releases and the Blue Book archive. What the PURSUE tranche supplies is the primary text itself, published intact under its Atomic Energy Commission cover sheet: not new facts, but the unmediated sound of the argument.
Status of the case
This is an archival document, and it should be read as one. It records what a room of scientists was willing to commit to paper on one afternoon in 1949 — not a present-day finding, and emphatically not a determination that anything unearthly crossed the New Mexico sky. The fireballs were investigated with the instruments of the time, which is to say mostly with human eyes, and testimony is not measurement; a distinguished physicist can be as mistaken as anyone about a light in the dark. That Teller and LaPaz disagreed proves only that the evidence before them was too thin to compel agreement, and thin evidence remains thin however eminent the people examining it. The All-domain Anomaly Resolution Office has made no modern determination about the events described here, and the document’s release is not an endorsement of any conclusion inside it. Its value is as evidence of how seriously the United States government took a mystery over its own atomic installations, and of what it chose to keep.