AS America marks 40 years since the last man set foot on the Moon, a scientist has launched an appeal for missing Moon rocks - after almost half of those collected have since disappeared.  As the last in a series of only 12 men to walk on the Moon and gaze back at the Earth from 250,000 miles away, Apollo 17 Commander Eugene Cernan and lunar module pilot Harrison "Jack" Schmitt wanted to bring back something symbolic.

As they wrapped up their third and final moonwalk on December 13, 1972, they paused to reflect on the magnitude of their achievement and the message of peace, hope and unity they felt it should represent to people back on Earth.  "To remind all the people of the world that this is what we are all striving for in the future, Jack has picked up a very significant rock," Cernan told mission controllers in Houston, standing alongside his partner on the lunar surface. The sample, comprised "many fragments, many sizes and many shapes, probably from all parts of the Moon, perhaps billions of years old, sort of living together in a very coherent, very peaceful manner," he noted.  –TG

Schmitt requested that pieces of the rock be distributed to museums and agencies worldwide, representing their hopes for the future of mankind.

Yet 40 years on, most of those goodwill gifts - and others brought back by the first men on the Moon, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin - have instead become symbols of greed, carelessness and criminality.

President Nixon distributed 269 fragments of Apollo 11 and Apollo 17 moon rock to 135 nations. Today, 159 of them are unaccounted for, either lost, stolen or destroyed.

In addition, each of America's states and the District of Columbia were given two pieces, one from each mission; of those 100 samples, 19 are missing, plus one belonging to Puerto Rico and another to the US Virgin Islands.

The hunt to locate them and restore them to the purpose for which they were intended, led by a law professor who was formerly a senior special agent in Nasa's Office of the Inspector General (OIG), has lasted for more than a decade.

As America marks the 40th anniversary this week of man's final lunar foray, reflecting on the accomplishments of the Apollo era and looking ahead to new space exploration challenges, he has issued a call for lunar larcenists to search their consciences and relinquish their haul.

"This was what the sacrifice of astronauts like Neil Armstrong and Gene Cernan was all about - they brought back the Moon to the people of the Earth. The Moon!" said Prof Gutheinz.

"Some people were in awe of it. Some people put it in boxes and forgot about it. Some people stole it. They stole the Moon and it's time we got it back."

As an undercover agent with the OIG, Prof Gutheinz led a sting operation that led to the recovery of Guatemala's Apollo 17 rock, which had been stolen from the state by a retired military officer, sold to a Florida businessman and then offered for sale for $5 million.

Since leaving the OIG ten years ago, Prof Gutheinz and his criminal justice students at the University of Phoenix, in Arizona, and others, have located dozens of rocks whose whereabouts were previously unknown. Among them were rocks presented to the people of Colorado, Missouri and West Virginia but found to have been retained for decades by past governors in their homes or offices.

Ireland's Apollo 11 rock was accidentally discarded at a landfill site. Nicaragua's ended up with a Las Vegas collector. Malta's Apollo 17 souvenir was stolen from a museum that failed to keep it under lock and key, Romania's was appropriated by dictator Nicolae Ceausescu and then sold to an unknown buyer as part of his estate following his death in 1989. Spain's was last thought to be in the possession of the former dictator General Francisco Franco's grandchildren.

Alaska's Apollo 11 relic found its way into the hands of a crab fisherman, Coleman Anderson, who claimed that he retrieved it in 1973 from the debris of a museum fire. When finally tracked down by Elizabeth Riker, one of Prof Gutheinz's students, in 2010, he launched a lawsuit against the state maintaining that he was the rightful owner and that if it wanted it back, they must pay him. TG