In 1968, a B-52 bomber carrying four nuclear bombs crashed in Greenland, near the Thule airbase:
Eventually, a remarkable operation would unfold over the coming months to recover thousands of tiny pieces of debris scattered across the frozen bay, as well as to collect some 500 million gallons of ice, some of it containing radioactive debris.
This is where the mystery of the lost US nuclear bomb gets interesting:
The high explosives surrounding the four nuclear weapons had detonated but without setting off the actual nuclear devices, which had not been armed by the crew.The Pentagon maintained that all four weapons had been “destroyed”.
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The [declassified documents obtained by the BBC under the US Freedom of Information Act] make clear that within weeks of the incident, investigators piecing together the fragments realised that only three of the weapons could be accounted for.Even by the end of January, one document talks of a blackened section of ice which had re-frozen with shroud lines from a weapon parachute. “Speculate something melted through ice such as burning primary or secondary,” the document reads, the primary or secondary referring to parts of the weapon.
By April, a decision had been taken to send a Star III submarine to the base to look for the lost bomb, which had the serial number 78252. (A similar submarine search off the coast of Spain two years earlier had led to another weapon being recovered.)
But the real purpose of this search was deliberately hidden from Danish officials.
One document from July reads: “Fact that this operation includes search for object or missing weapon part is to be treated as confidential NOFORN”, the last word meaning not to be disclosed to any foreign country.
“For discussion with Danes, this operation should be referred to as a survey repeat survey of bottom under impact point,” it continued.
But the underwater search was beset by technical problems and, as winter encroached and the ice began to freeze over, the documents recount something approaching panic setting in.
As well as the fact they contained uranium and plutonium, the abandoned weapons parts were highly sensitive because of the way in which the design, shape and amount of uranium revealed classified elements of nuclear warhead design.
But eventually, the search was abandoned. Diagrams and notes included in the declassified documents make clear it was not possible to search the entire area where debris from the crash had spread.
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The view was that no-one else would be able covertly to acquire the sensitive pieces and that the radioactive material would dissolve in such a large body of water, making it harmless.
(Hat tip to Todd.)