50-Year Old Moon Samples Still Reveal New Discoveries

Amazingly, the samples of material from the moon retrieved by the Apollo missions are still providing new insights more than 50 years later, in this case how tiny glass beads that litter the lunar surface are telling us about the explosive volcanic plumes that formed them 3.3 to 3.6 billion years ago.

"We've had these samples for 50 years, but we now have the technology to fully understand them," said Ryan Ogliore, a physics professor at Washington University in St Louis, in a statement. "Many of these instruments would have been unimaginable when the beads were first collected."

The tiny beads, less than a millimeter in size, are embedded in lunar rocks and mixed into the lunar regolith. They come in two varieties, orange and black, and were produced when drops of lava in plumes that violently erupted out of volcanoes cooled quickly in the cold vacuum on the lunar surface. Around 3.5 billion years ago, the moon was drastically volcanically active, forming the dark patches of the lunar maria that today form the "face" of the "Man in the Moon."

"The beads are tiny, pristine capsules of the lunar interior," said Ogliore. "They're some of the most amazing extraterrestrial samples we have."

Ogliore was part of a team led by Thomas Williams, Stephen Parman and Alberto Saal of Brown University in Rhode Island, who deployed a variety of modern microscopic analysis techniques on the beads to learn more about the volcanic conditions in which the beads formed.

The main instrument used was a NanoSIMS 50 ion microprobe at Washington University, which can perform spectrometry at the atomic scale, identifying elements and isotopes, and probing nano-scale structure.

To avoid the subject material being exposed to Earth's atmosphere and reacting with its oxygen, the ion beam cored into the samples, extracting the beads from within them, and then taking care that the material was protected from our atmosphere. The samples were then subjected to a number of analysis techniques, including atom probe tomography, scanning-electron microscopy and energy dispersive X-ray spectroscopy.

"Even with the advanced techniques we used, these were very difficult measurements to make," said Ogliore.

The measurements told the team about the pressure, temperature and chemistry of the environment that the beads formed in. Indeed, their very existence is proof that the moon had explosive eruptions, "something like the fire fountains that you can see in Hawaii today," said Ogliore.