US President Richard Nixon donated to 135 states and fifty US states small pieces of rock from the moon, which were collected by astronauts on the Apollo 11 and Apollo 17 missions. But many of them are missing today.
Some of these stones are no longer in their original location, or have been stolen and destroyed over time. We introduce you to the history of some of them.
This list is based on the research of a former NASA employee, Joseph Gutheinz, known as the "moon rock hunter" nicknamed by his students, and the space history website collectSpace.
Afghanistan
The two pieces donated to Kabul have disappeared.
Cyprus
One of the stones to be given to Cyprus was never delivered due to the Turkish occupation of part of the island in July 1974 and the assassination of the American ambassador a month later.
Honduras
The stone that was given to Honduras, part of the Apollo 17 mission was recovered in 1998 by Joseph Gutheinz himself and a US Postal worker, Bob Cregger, during an operation called "Eclipse of the Moon".
A Honduran army colonel sold the stone to a Florida businessman, Alan Rosen, for $50,000. The latter tried to sell the stone for 5 million dollars. The stone was finally found to be returned to Honduras.
Ireland
The stone that was donated to Ireland was displayed at the Dunsink Observatory in Dublin, which was destroyed in 1997 after it caught fire. The ruins of the observatory, including the sample, ended up in a waste collection point north of the capital.
Libya
Pieces of moon rock given to Colonel Muammar Gaddafi, then the leader of Libya, have disappeared.
Malta
The gift to Malta, taken from Apollo 17, was stolen from a museum in May 2004. It has not yet been found.
Nicaragua
The Nicaraguan rock from Apollo 17 is thought to have been sold to a person in the Middle East, for an amount believed to be between $5-10 million.
The stone brought by Apollo 11 ended up in the hands of a casino owner in Las Vegas, who exhibited it for a while at the Moon Rock Cafe. After his death, the stone was given to NASA, which returned it to Nicaragua.
Romania
A Bucharest museum displays the Apollo 11 stone.
The Apollo 17 mission stone is believed to have been sold by the descendants of dictator Nicolae Ceausescu, who was executed along with his wife Elena on Christmas Day 1989.
Spain
Pieces of Apollo 17 that were handed over to Spain were put on display at Madrid's Naval Museum after being gifted to the family of Admiral Luis Carrero Blanco, a powerful figure in the Franco regime who was killed by the Basque separatist organization ETA in 1973.
The stone brought back by Apollo 11 is missing, but is thought to have remained in the family of former dictator Franco.