Nearly 20 vials of Moon dust collected by astronauts Neil Armstrong and Buzz Aldrin were discovered earlier this month in the Space Sciences Laboratory at the University of California Berkeley campus where they have sat for nearly half a century, forgotten.

They were discovered by archivist Karen Nelson as she worked to review and clean out artifacts from Berkeley’s Lab’s warehouse.

“They were vacuum sealed in a glass jar,” she said in a statement posted on the institute's site. “We don’t know how or when they ended up in storage.”

Accompanying the vials was a copy of the paper “Study of carbon compounds in Apollo 11 and Apollo 12 returned lunar samples,” which was published in the Proceedings of the Second Lunar Science Conference in 1971.

One of the authors of the study was Melvin Calvin, who was also an associate director of Berkeley Lab and perhaps the one who forgot to send the the samples back to NASA after the publication.

Nelson said she has since contacted the Space Sciences Laboratory who were “surprised" the warehouse still had the samples, and then contacted NASA, who asked that the samples be returned.

This is not the first time NASA has been confronted with missing or stolen space objects.

In a press release issued by the agency’s inspector general in 2011, the agency reported that more than 500 pieces of moon rocks, meteorites, comet chunks and other space material have been stolen since 1970, including 218 samples that were stolen and later returned and 24 moon rocks and chunks of lunar soil reported lost in 2010.

As reported by the Associated Press, the agency explained in the statement that it had loaned at that point more than 26,000 samples using a system that “increases the risk that these unique resources may be lost” due to a lack of controls.

Some measures to increase monitoring began, according to the report, after a moon sample loaned to an observatory in Delaware went missing; meanwhile, the astronomers claimed the object had been returned.

For this reason the agency’s inspector general decided to audit nearly 25 percent of the loaned samples, 19 percent of which researchers either couldn’t account for or that NASA records indicated had been destroyed or loaned to someone else.

In one case, a researcher was in possession of nine lunar samples he had been borrowing for nearly 35 years and 10 pieces of meteorites he’d had for 14 years - neither of which, according to the Associated Press, he had worked on.