Apollo 17, the last manned mission to the Moon, returned home in December 1972. Whilst earlier missions had only brought back tiny fragments of moon rock for study, the later missions were confident enough to take a reasonable quantity.
So when the mission touched down, the Nixon administration decided to use some of the material as a peace or goodwill gesture, and ordered the distribution of moon rocks to 135 foreign heads of state and the 50 US states and their provinces.
The Moon rocks were labelled sample 70017. Each was encased in an acrylic button mounted to a plaque, with the intended recipient's flag, if appropriate, which had also been flown to the Moon.
A letter, signed by President Nixon and dated March 21, 1973, accompanied each moon rock.
"On behalf of the people of the United States I present this flag, which was carried to the Moon... and its fragment of the Moon obtained during the final lunar mission of the Apollo program.
"If people of many nations can act together to achieve the dreams of humanity in space, then surely we can act together to accomplish humanity's dream of peace here on Earth," it read.
However, not all of the moon rocks were treated with suitable reverence and, untracked by NASA, some vanished. Recently, however, one reappeared.
Former Colorado Governor John Vanderhoof was given the rock in 1974, and confirmed in June that he still had it, despite long having left office. Claiming that he wasn't aware anyone else was interested, he offered it to a museum, and it has gone on display this week.
Space collectors and investors will have raised eyebrows at the idea that no one was interested. In purely financial terms moon rock in the form of moon meteorites can be worth over $2,000 per gram.
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