This debris cloud was generated yesterday in 1952 by the nuclear blast codenamed Dog, which was part of Operation Tumbler-Snapper, a series of tests that occurred at the Nevada Test Site that year. The people you see in the image are just a few of the 2,100 marines who observed the explosion. Last month Chatham House released a sobering nuclear study showing that there have been thirteen incidents since 1962 that qualify as “near use” of nuclear weapons. In two of those—the famed Oleg Penkovsky incident and the less famous but more serious Stanislaw Petrov incident—nuclear holocaust may have been averted only because individuals disobeyed orders. Chatham House also details many instances of “sloppy practice.” Two examples: President Jimmy Carter once left the U.S. nuclear launch codes in a suit that was taken to the dry cleaners, and in 1981 when Ronald Reagan was shot, his bloody pants containing the launch codes ended up in the hands of FBI agents who had no authorization to possess them. There are instances of sloppy practice from as recently as 2013. If you’re in the mood for some sobering reading, the report is here.