On Aug. 4, 1972, U.S. military pilots witnessed something strange in North Vietnam: More than two dozen sea mines suddenly, and without apparent explanation, exploded in the water. Now, Professor of Aerospace Engineering Sciences Delores Knipp and her colleagues have dug into this decades-old mystery and discovered an unlikely culprit—the sun. 

Knipp explained that she has a “passion for rooting around in dark, dusty archives.” So to solve the case of the exploding mines, her team uncovered several historical documents that had been largely forgotten.

The researchers discovered that the sun had shot off several bursts of energy, called solar flares, in early August 1972. The resulting solar storm was likely worse than scientists at the time thought and may have disrupted power grids in North America—and led to the surprising explosions in Vietnam.