Lunar samples collected by Apollo missions are a precious thing, with some specifically kept sealed for future studies – or at least until we can go back to the moon to collect some more. Now researchers have used a new technique to get as much data as possible from a single grain.
As reported in Meteoritics & Planetary Science, researchers at the Field Museum in Chicago used atom probe tomography (APT), a technique that's usually used by material scientists to look at how to improve industrial processes that make steel and nanowires. The method allowed the team to carve out a small grain of moondust just a few hundred atoms wide from the sample. They then used a laser to bump off atoms one by one in order to analyze the sample's composition and the origin of the atoms.
“We're analyzing rocks from space, atom by atom,” first author Jennika Greer, a graduate researcher at the Field Museum and the University of Chicago, said in a statement. “It's the first time a lunar sample has been studied like this. We're using a technique many geologists haven't even heard of.”
The technique allows the researchers to compare the commonalities and differences between the weathered surface soil and the unexposed lunar regolith. No other method can recreate the atomic composition of a sample in three dimensions and still be used for future studies. This allowed them to identify products of space weathering, including water, helium, and iron. Knowing the amount of these resources could help researchers plan for a future permanent base on the Moon.
"We can apply this technique to samples no one has studied," co-author professor Philipp Heck added. "You're almost guaranteed to find something new or unexpected. This technique has such high sensitivity and resolution, you find things you wouldn't find otherwise and only use up a small bit of the sample."
But it is not just lunar soil. Over the next few years, two missions will bring back pristine samples from asteroids, including the first subsurface sample.
"It's great for comprehensively characterizing small volumes of precious samples," Greer said. "We have these really exciting missions like Hayabusa2 and OSIRIS-REx returning to Earth soon – uncrewed spacecraft collecting tiny pieces of asteroids. This is a technique that should definitely be applied to what they bring back because it uses so little material but provides so much information."
NASA has provided funds to the Field Museum for three more years of lunar sample analysis using APT to work out the water content and the space weathering of several different Apollo samples.