On March 1, 1954, the United States exploded a hydrogen bomb on Bikini Atoll that was far more powerful than even the scientists that built it had expected.
The blast, dubbed “Castle Bravo,” had a force of 15 megatons rather than the expected 6 megatons.
The resulting mushroom cloud of superheated air, water and fallout reached 130,000 feet (24.6 miles) in altitude — soaring well into the stratosphere.
Contamination from the largest above-ground test of a hydrogen bomb in U.S. history eventually spread to four continents.
The blast was 1,000 times more powerful than from the atomic bomb dropped on Hiroshima in August 1945.
The image of Bikini Atoll to the right was captured by the Operational Land Imager on the Landsat 8 satellite on August 19, 2013. Clearly visible is the crater left by the "Castle Bravo" bomb.
Between 1946 and 1958, 23 nuclear bomb tests were conducted at the atoll.
Bikini islanders and their descendants have lived in exile since they were evicted from their homes before the first weapons tests in 1946. Some returned after the U.S. declared the atoll safe in the early 1970s.
But they were removed again after ingesting high levels of radiation in food grown in what was found to be still-contaminated ground.
Fallout from the 1954 blast, which had been intended to be top secret, also rained down on nearby Rongelap and Utirik atolls, leading many there to later suffer from radiation sickness.
Crewmembers of the Japanese tuna fishing vessel Daigo Fukuryu Maru (“Lucky Dragon No. 5”) were also exposed to high levels of fallout as they sailed past at 40 miles from the blast site. All of the crew became sick, and many eventually died from their illnesses.
Eighty-year-old survivor Matashichi Oishi described the experience to those gathered at the March 1 commemoration.
“I remember the brilliant flash in the west, the frightening sound that followed and the extraordinary sky which turned red as far as I could see,” he said.