Vials of moon dust that the astronauts of Apollo 11, the first trip to the moon, brought back were recently found stored in a California lab warehouse were they had been sitting for 40 years, Fox News reported.

The samples were collected by well-know astronauts Neil Armstrong and Buzz Aldrin. Archivist Karen Nelson was going through artifacts at the Lawrence Berkeley National Laboratory when she came across the small vials.

There were 20 vials, all with handwritten labels that read "24 July 1970."

"We don't know how or when they ended up in storage," Nelson said.

Along with the sample Nelson found an academic paper titled "Study of carbon compounds in Apollo 11 and Apollo 12 returned lunar samples." The paper was written by multiple members of the University of California, Berkeley's Space Sciences Laboratory.

The most notable co-author of the paper was Nobel-Prize winning chemist Melvin Calvin, who worked with NASA to help prevent moon contamination when the Apollo 11 mission landed. He also researched how to keep the astronauts safe from moon dust contamination that may have contained unknown pathogens.

Like a letter lost in the mail, these moon dust samples were meant to be returned to NASA, but were accidentally placed in storage.

NASA's Apollo astronauts brought back 842 pounds of lunar samples between 1969 and 1972. Most of these samples are unaccounted for.

Out of 68 grams of lunar material that was brought back from the mission, only 50 grams were returned, said Ryan Zeigler, NASA's Apollo sample curator at the Johnson Space Center in Houston.

NASA had previously thought that the 18 unaccounted for grams had been destroyed during experiments.

"Given the lengths taken to preserve the samples, this does not appear to have been an attempt of deliberate deception, but likely a miscommunication where some of the material was retained for ongoing or expected future studies which never happened," Zeigler wrote in an email to Fox News. "Why they were never returned is unclear."

The vials have been returned to NASA's sample vault. Ziegler stated that he does not know when the samples will be studied again, but he believes that there will be uses in the future for the rare material.