In late 1948, glowing green objects began streaking over Los Alamos and Sandia. Air Force meteor consultant Lincoln LaPaz triangulated their paths, ruled out ordinary meteors, and told the military the fireballs were probably man-made.
Around Albuquerque, the desert night was already used to secrets. It was 1948, and within a hundred miles of the city sat two of the most sensitive installations in the young Cold War: the Los Alamos laboratory, where the atomic bomb had been designed, and Sandia Base, where the weapons were assembled. On the night of December 5, the flight crews of a civilian airliner and a military transport looked out their windows within minutes of each other and reported the same thing: a bright green ball of light streaking almost horizontally across the New Mexico sky, moving too flat and too slowly to be a shooting star.
Over the next three years, hundreds of similar sightings piled up over the American Southwest, according to a history of the case by HISTORY. Green fireballs became a regular feature of the New Mexico night, seen by pilots, atomic-site guards and Los Alamos physicists. They almost never turned up anywhere else. And the U.S. Air Force never publicly settled what they were.
The reason the case still matters is that the investigator who took it most seriously was not a UFO enthusiast. He was one of the country’s leading experts on things that fall out of the sky.
Dr. Lincoln LaPaz ran the University of New Mexico’s Institute of Meteoritics and was widely considered the top American authority on meteorites at the time, per a Wikipedia biography drawn from later academic sources. During World War II he had helped the U.S. track Japanese “balloon bombs” by working backwards from where their debris landed - the kind of trajectory work that would matter here too.
When Kirtland Air Force Base’s Office of Special Investigations started getting green fireball reports in late 1948, they called LaPaz. He interviewed more than a hundred witnesses and, on December 12, saw one himself. Because the object was seen over Los Alamos the same evening, he could triangulate its path from two locations.
His conclusion was awkward for everyone. The flight path was almost flat, only a few degrees above the horizon, and the object moved far too slowly to be a normal meteor - which typically enters at a steep angle and burns out in a couple of seconds. There was no trail of dust or sparks, no reported sonic boom, and no fragments on the ground when searchers went looking, per the Wikipedia summary of the Green fireballs case files. In classified letters to the Air Force he said the fireballs were probably not natural. They were most likely, he wrote, “unconventional defensive devices” being tested by the United States - or, more worryingly, Soviet reconnaissance craft.
In February 1949 the Air Force convened a closed-door conference at Los Alamos itself. This was not the whispered “hush-up” of popular UFO memory. The attendees, according to declassified files summarised on Wikipedia, included members of the Air Force’s early UFO study Project Sign - the direct ancestor of the effort that would later become Project Blue Book - together with atmospheric physicist Joseph Kaplan, Manhattan Project veteran and future H-bomb architect Edward Teller, and LaPaz himself. The meeting ended without an explanation for what people were seeing.
The Air Force’s response was Project Twinkle. Approved in December 1949, it was meant to put a network of tracking cameras, spectrographs and radios into the New Mexico desert, so that at least one instrument would eventually catch a green fireball and turn a strange story into hard data.
That is not how it worked out. The project was thinly funded from the start, and observers spent long shifts staring at empty desert. When Twinkle was quietly wound down about two years later, it had failed to capture a single green fireball on film. The final report leaned toward a natural explanation - probably some unusual meteor variant - and dropped the matter.
Internally, though, several of the people closest to the case refused to sign on. A 1952 follow-up review by the USAF Directorate of Intelligence, cited in the same Project Twinkle entry, noted that “no scientific explanation” had actually been found, and that some scientists still believed the fireballs were man-made. Anthony Mirarchi, the physicist who had been Twinkle’s first director, went further in public - he said he thought they were Russian.
The green fireballs sit awkwardly in the modern UAP file. There is real, contemporary evidence they happened: multiple witnesses across independent agencies, cross-referenced sightings, a formal Air Force investigation. There is very little clean, instrumented evidence of what they actually were. Modern skeptics point out that unusual bright meteors do exist, that nickel in a meteor can flash green, and that a wave of sightings can prime observers to see more of them.
But LaPaz’s flat trajectories and low speeds have never been well explained by that view. And the geography is striking: even other 1948 cases - like the death of Air Force Captain Thomas Mantell chasing a bright high-altitude object over Kentucky - do not show this same pattern of repeat, localised sightings clustered on the country’s most secret military infrastructure.
Almost eighty years on, the Air Force’s file on the green fireballs still reads: possibly natural, not proven. The astronomer they hired never agreed.
Between May and December 1946, Scandinavians reported roughly 2,000 fast, silent objects, and about 200 were tracked on radar. It became the world's first modern government UFO investigation - and the leading suspect was not aliens, but a captured German rocket program.
Less than three months after Pearl Harbor, radar flagged something off the California coast and the guns opened up for an hour over a blacked-out city. The Army said 15 planes were up; the Navy said none. Decades later, the leading suspect was a stray weather balloon.
On a clear morning in suburban Melbourne, more than a hundred students and teachers watched a domed silver object sink behind the pines and, some say, land. Sixty years later, the tidiest explanation - a stray radiation-sampling balloon - still doesn't fit the wind.
