When you look at the moon looming over the Earth, especially a rising harvest moon blazing bright orange and red, you don’t think about a tiny grain of dust up there.
But Kate Burgess does, she’s studied dozens of lunar grains in her work as a geologist at the U.S. Naval Research Laboratory (NRL).
“The idea that you can walk outside and see the moon and think, ‘These are little particles of dust that used to be up there, and I get to work with them in my lab,’” Burgess said, “that’s pretty cool.”
A lot of studying of those samples through a microscope has taken place over the years, and her diligent work has paid off. Burgess is being recognized with an award from the Microanalysis Society, receiving the Kurt F.J. Heinrich award for her work over the past decade.
Lunar samples of dust particles and rock have been brought back to Earth for more than half a century, ever since Neil Armstrong became the first person to step foot on the Moon in 1969. One of Burgess’s primary findings from these samples is helium trapped inside tiny grains of moon dust.
“Scientifically it wasn’t a huge surprise,” Burgess said. “We know that there is a lot of helium in the solar wind, along with hydrogen.”
Scientists studying Moon material found helium, but it was at the bulk level, Burgess said. Her research narrowed in on single particles, single dust grains that had not previously been measured in detail at the nanoscale, which refers to material measuring 1-100 nanometers. One nanometer is a billionth of a meter. By comparison, a human hair is about 100 microns, or more than 1,000 times larger.
The helium Burgess found was in a vesicle, which is a small bubble, an open space inside the grain that traps the helium. Finding helium at that scale, which was in an individual vesicle, was new.
“Working with lunar samples is definitely kind of mind blowing these days,” Burgess said. “Finding helium in one of the vesicles was probably the single coolest discovery we made.”
She wasn’t looking for helium when she saw it for the first time because vesicles weren’t the initial focus of the research.
“The helium created a pretty dramatic signal,” she said. “Scientifically, it confirms where exactly the helium is trapped in the lunar soil, and it shows the benefit of nanoscale examination of geologic and planetary samples.”
Burgess worked exclusively on samples brought back by the Apollo 17 mission in 1972, which was the last time U.S. astronauts walked on the Moon. The crew, which consisted of Eugene Cernan, Ronald Evans, and Harrison “Jack” Schmitt, collected the oldest known lunar rock unaltered by the impact of a meteor.
Schmitt, a geologist like Burgess, was the first scientist to explore the surface of the moon. Burgess said with the samples returned from the Apollo mission, scientists were able to develop the current theory of how the moon formed, which is believed to have happened when an object the size of Mars hit the proto-Earth in the earliest stages of its development. Over time, the Earth cooled, causing the formation of a solid crust, and allowing water on the surface. A vast amount of proto-Earth flew into space following the impact. While much of the material flew into the great unknown, enough of it was trapped by the pull of the Earth to form the Moon.
The impact formed a large lava plain within the Imbrium Basin, one of the larger craters in the Solar System. The Imbrium Basin formed from the collision of a proto-planet. Lava flooded the crater to form a flat volcanic plain seen from Earth today.
“The volcanic activity that filled the basin brought up material that helps us understand what was deeper in the magma ocean, under the crust,” Burgess said.
Samples from the Moon are well curated. Not only did Burgess know which lunar mission the samples she worked on came from, she was able to see the astronauts collecting the samples from videos currently online. Burgess said it’s pretty phenomenal that we are able to search by sample number, and hear what the astronauts are saying as they collect that particular sample.
Among the common minerals on the lunar surface, helium is trapped most easily by ilmenite, an iron-titanium oxide. Ilmenite in lunar soils contains as much as 10 times more helium than other common minerals. After the return of the Apollo samples, scientists were able to determine ilmenite trapped more helium.
“Once we started looking,” Burgess said, “it was clear in our samples as well.”
Knowing that the helium is in ilmenite primarily, and that it’s concentrated in the vesicles could aid resource utilization to get at the helium. We now know where most of the helium is, she said.
While study of Moon particles continues, it may be a decade or more before scientists can get samples from Mars. Probes are collecting samples, but nothing has come back yet in the midst of planning a manned mission to the Red Planet. If that day comes, Burgess might have a second heavenly body to ponder when she steps outside of her laboratory after examining Mars particles more closely.
Burgess is currently the lead investigator for a NASA Apollo Next-Generation Sample Analysis Program project. This research compares soils taken from large boulder overhangs shadowed from solar wind to nearby soils fully exposed to solar wind. The comparison helps scientists better understand how the lunar surface is altered by solar wind at the nanoscale.
Specialized sample-handling techniques that exist today, such as those needed for working with frozen samples, could help with the study of future samples from the Moon, asteroids or Mars.
New samples from the Moon may soon be available for study by Burgess and her colleagues. If all goes as planned, NASA’s Artemis program will deliver humans back to the lunar surface in the next few years. Planned missions include crewed and robotic exploration of the lunar landscape.
Another NASA mission, dubbed OSIRIS-REx, travelled to asteroid Bennu, which is close to Earth. The explorer is expected to return in 2023.
Scientists will be waiting a bit longer to study particles from the Red Planet under the microscope. Plans call for Mars samples to be returned to Earth in 2031.
Burgess was surprised to win the Heinrich award, which honors scientists for their work less than 15 years from receiving a degree in their field, and who have made distinguished technical contributions to the field of microanalysis. Burgess earned her doctorate in geology from Brown University in 2012 and began her post-doctoral work at NRL in 2014. She became part of the staff in 2017 and now works in NRL’s Nanoscale Materials Section.
“It’s a huge honor,” she said. “I immediately looked over the list of people who have won it in the past few years. It’s kind of an intimidating list, so it’s a huge honor to be included among them. I don’t tend to think of myself in those kind of terms. I’m really excited about it.”
The award has placed Burgess in lofty company. Previous awardees include Lena Kourkoutis, last year’s winner who is using cryogenic microscopy techniques; and Stephen Pennycook, Vinavak Dravid, and Richard Leapman, who have done significant work in electron microscopy.
Heinrich was a pioneer in the field of microscopic research. The award named in his memory will be presented at the Microscopy and Microanalysis meeting in August.
About the U.S. Naval Research Laboratory
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