The Sun Caused 4,000 Sea Mines To Detonate During the Vietnam War

In August 1972, a series of American magnetic sea mines situated around northern Vietnam began to detonate all at once. These mines were strategically positioned to explode near ships, but it wasn’t maritime traffic that triggered them.

While US forces reported numerous mine explosions, estimates suggest the actual number might have reached up to 4,000. So what could have caused such a widespread detonation? Remarkably, it was the Sun.

Historically powerful solar storms

In August 1972, one of the most powerful solar storms ever recorded occurred. That month, the Sun had displayed increased solar activity before unleashing a series of extremely powerful solar flares - intense eruptions of radiation caused by the interactions of powerful magnetic fields within the star.

The burst of energy from a solar flare can be followed by a coronal mass ejection (CME), a magnetic cloud of radioactive particles that's expelled from the Sun into the cold expanse of interplanetary space at unfathomably high speeds. While the Sun is almost 93 million miles away from the Earth, normal CMEs can make the journey in just one or two days .

August 4, 1972

The most intense flare of the August 1972 solar storms erupted on the 4th, releasing a magnetized and radioactive cloud. This cloud reached Earth in just 14.6 hours , setting a record for the fastest coronal mass ejection (CME) travel time that still stands today . The CME's impact on Earth's magnetosphere resulted in exceptionally bright auroras appearing far south of their usual range, with some visible as far as Spain.

When the flare arrived, sensors and monitoring equipment were covered with charged particles, causing their readings to go off the charts. Similarly, magnetometers were overwhelmed. The hazards from such powerful storms extend beyond the surface; satellites and spacecraft can suffer severe damage from CMEs, with one satellite experiencing about two years' worth of wear from this storm.

Adding to the concern, the storm occurred between Apollo 16 and 17 , the latter scheduled to launch a few months later. Had the mission coincided with the storm, the astronauts would have been exposed to a hazardous level of radiation, even within the command module. If they had been on a moonwalk during the event, the radiation dose could have been lethal.

Sea mines detonated off the coast of Vietnam

American sea mines positioned around northern Vietnam were magnetically triggered. The sensors within these mines constantly monitored the magnetic fields around the devices, which became altered whenever a ship entered their proximity. The sea mines had been placed off the coast of Vietnam as part of Operation Pocket Money , which was intended to block maritime trade in the region.

The sheer power of the August 1972 solar storms was enough to distort the Earth's magnetic field and trigger the sea mines off the coast of Vietnam. At the time, the US military knew such events could interfere with systems on Earth, but they didn't understand to what extent this could happen.

New appreciation for the August 1972 solar storms

In 1972, the strange happenings caused by the enormous coronal mass ejection were seen as unremarkable and mostly fell under the radar of researchers at the time. It wasn't until Delores Knipp, an esteemed research professor at the University of Colorado Boulder, began looking into the event that the true scale of the Sun's activities back then was realized.

Knipp's research began after a chance conversation with a colleague , who, at the time, was working at what would later become NOAA's Space Weather Prediction Center . The latter had witnessed US Navy officials enter a meeting with his boss, and while he'd been unable to hear the details, he knew it was about a then-recent solar storm and its impacts on the military.

The 1972 solar storms are a warning about the power of the Sun

After learning about this, Knipp dived into military archives. She found a document that had been declassified in the 1990s that contained information about the spontaneous detonation of sea mines in Asia. With some more digging, she realized estimates made at the time significantly low-balled the power of the solar storm. She believes it was actually much closer in severity to the 1859 Carrington Event , the largest geomagnetic storm ever recorded.

Despite this, many failed to recognize its significance. "I think people forgot about it," Knipp said in 2018. "They didn't know about the sea mine problem and the effect on the power grids got published in engineering journals, not science journals."

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Knipp regards the August 1972 solar storms as a warning about how vulnerable we are to the mind-boggling power of the Sun.