Roger Rasmussen stood at the base of the Oscura Mountains staring at a boiling cloud of ash and smoke rising up in southern New Mexico's Jornada del Muerto desert. It was 5:30 a.m. on July 16, 1945.

Not a minute before, Rasmussen had been face down on the ground, arms over his head and eyes shut, waiting for the blast that would soon lead to the end of World War II and hearken the dawn of the nuclear era.

"I was buried, eyes shut tight, and it was bright like daylight," he said during an April interview at the Los Alamos Historical Museum in New Mexico. "It all boiled up and I could see all the colors."