It began with an unusual flash detected off the coast of South Africa by an aging American satellite — and to this day, debate continues over whether this odd Cold War event involved an illicit atmospheric nuclear test.
The strange story of the “South Atlantic Flash,” better known as the Vela Incident, began on Sept. 22, 1979. At that time, Vela 6911, a satellite in a constellation developed by the United States for the specific purpose of detecting nuclear detonations, observed something that immediately alarmed officials: a peculiar flash of light emanating from somewhere over the South Atlantic Ocean.
A significant part of what concerned U.S. officials at the time had been the double flash of light detected during the event — a distinctive feature that strongly resembled the flashes produced by a nuclear explosion in Earth’s atmosphere. The characteristic double flash results from the rapidly changing brightness of the fireball and shock wave produced by an atmospheric nuclear detonation, creating a distinctive optical signature that Vela’s sensors were specifically designed to recognize. The South Atlantic event, therefore, seemed like a prime candidate for a secretive nuclear test being carried out by an unknown party — but if that were the case, who was responsible?
What do we know?
U.S. officials responded to a possible nuclear test
Then-President Jimmy Carter was promptly alerted to the situation, as evidenced in diaries the former U.S. leader would publish years later. “There was indication of a nuclear explosion in the region of South Africa,” Carter wrote in an entry on the same date of the event. A later entry penned the following February would go on to add that “We have a growing belief among our scientists that the Israelis did indeed conduct a nuclear test explosion in the ocean near the southern end of Africa.”
Despite that belief regarding the possibility of a clandestine nuclear test, a scientific panel assembled in 1980, chaired by MIT professor Jack Ruina, eventually put forward an alternative explanation: that the flash had more likely been an anomaly caused by a small meteoroid striking the satellite.
Notably, the panel did not rule out the possibility of a nuclear explosion at the time, although the alternative they put forward remained controversial among scientists and intelligence officials.
Documents and government insiders surface
By the turn of the 21st century, formerly classified documents began to surface that revealed the extent of the inner tensions between U.S. government agencies over what caused the Vela incident.
Among the critics of the debris-induced “anomaly” hypothesis had been Defense Intelligence Agency Vice Director Jack Varona. According to documents released in 2006, Varona said the investigations by the 1980 scientific panel had been a politically motivated “whitewash,” and that evidence collected by the U.S. intelligence community included detections “unique to nuclear shots in a maritime environment,” based on an analysis by the Naval Research Laboratory.
Varona wasn’t alone. Other former intelligence officials who came forward over the years included Stansfield Turner, the former Director of Central Intelligence during the Carter administration, who in 2003 described the Vela detection as a “man-made phenomenon.”
Similar views were advanced by retired CIA officer Tyler Drumheller, who in 2006 wrote that he had sources at the time who “collectively provided incontrovertible evidence that the [South African] apartheid government had in fact tested a nuclear bomb in the South Atlantic in 1979, and that they had developed a delivery system with assistance from the Israelis.”
What remains unknown?
Scientists revisit the mystery
While we still don’t know if the South Atlantic Flash was a nuclear test, several scientists have reexamined the available evidence within the last decade, and what they found has lent further weight to the idea that the Vela incident had involved a detonation of some kind.
Among the most significant assessments, a 2017 study by Christopher Wright and Lars-Erik De Geer combined modern research into interplanetary dust and hypervelocity impacts with revelations from recently declassified documents, as well as publicly available information that had been previously overlooked.
Their conclusion: while no model was presented for the tenuous “meteoroid” theory advanced by the May 1980 scientific panel, the double flash observed by the Vela satellite in 1979 was indeed “consistent with a nuclear explosion, albeit detected by an aged satellite for which background modulation was abnormal and/or commenced earlier,” adding that additional radionuclide and hydroacoustic evidence existed which supported the conclusion “that the Vela Incident was a nuclear weapon test explosion.”
Wright and De Geer weren’t alone either. A 2022 study examined data collected by NASA’s Nimbus-7 satellite just 16 minutes and 44 seconds after the double flash over the South Atlantic, which suggested a disturbance in the ozone layer that appeared to be consistent with a blast-generated shock wave.
Still, some of the original members of the 1980 scientific panel have defended its work amid the more recent scientific studies. Richard Mueller, who served as the panel’s youngest member at the time, defended the group’s conclusions in a November 2019 oral history conference, maintaining that the chances the Vela incident had involved a nuclear event were “as close to zero as it gets.”
This determination, Mueller argued, was made despite early interpretations by many panelists that a nuclear event had seemed most likely. Wright and De Geer, both of whom attended the 2019 oral history conference, were among the participants that pushed back on Mueller’s views.
Who was responsible?
Amid the mounting evidence over the last several decades suggesting the Vela incident was indeed a nuclear test, debate continues over who was most likely to have been responsible.
Although suspicions have long centered on a cooperative — and secret — strategic effort between apartheid-era South Africa and Israel, publicly available evidence remains lacking, and a fair amount of information in declassified documents that could point to this possibility remains redacted.
The mystery remains
Thus, after more than four decades, questions continue to linger over the famous Vela incident, including what nations might have been involved in such a test if it occurred. Despite that uncertainty, one thing does seem evident: information conveyed in unredacted portions of declassified records, combined with modern scientific analyses, increasingly point to the likelihood that the strange “South Atlantic Flash” in 1979 was anything but natural.