The Apollo 17 mission, which took place in 1972, was NASA’s final mission to the Moon. These astronauts returned some lunar soil to Earth so that scientists might continue to analyze it in their laboratories. Because humans haven’t visited the Moon in nearly 50 years, every lunar sample is valuable. We must make them count now and in the future for researchers.
Scientists discovered a novel approach to assess the chemistry of the Moon’s soil using a single particle of dust in a new study published in Meteoritics & Planetary Science. Their method could help us learn more about the conditions on the Moon’s surface, as well as the production of valuable resources like water and helium.
“We’re analyzing rocks from space, atom by atom,” says Jennika Greer, the paper’s first author and a PhD student at the Field Museum and University of Chicago. “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.”
“We can apply this technique to samples no one has studied,” Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and co-author of the paper, adds. “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.”
The technique is known as atom probe tomography (APT), and it’s typically utilized by materials scientists to improve industrial operations like steel production and nanowire production. However, because of its ability to evaluate small amounts of materials, it’s an excellent option for investigating lunar samples.
The Apollo 17 sample contains 111 kilograms (245 pounds) of lunar rocks and dirt, which isn’t much in the big scheme of things, so researchers must make good use of it. Greer just needed a single grain of soil, roughly the width of a human hair, for his examination.
It’s great for comprehensively characterizing small volumes of precious samples. We have these really exciting missions like Hayabusa2 and OSIRIS-REx returning to Earth soon uncrewed spacecrafts 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.
Jennika Greer
She discovered pure iron, water, and helium, which generated as a result of the lunar soil’s interactions with the space environment, in that tiny grain. Getting these valuable nutrients from lunar soil could enable future astronauts stay on the Moon longer.
Greer carved a tiny, super-sharp needle into the surface of the minuscule grain using a focussed beam of charged atoms to investigate it. A sheet of paper is hundreds of thousands of atoms thick, while this point was just a few hundred atoms wide.
“We can use the expression nanocarpentry,” says Philipp Heck. “Like a carpenter shapes wood, we do it at the nanoscale to minerals.”
Greer shot the sample with a laser once it was inside the atom probe at Northwestern University, knocking atoms off one by one. The atoms collided with a detector plate as they flew off the sample. It takes longer for heavier elements, such as iron, to reach the detector than lighter elements, such as hydrogen.
The gadget can determine the type of atom at that place and its charge by monitoring the time between the laser shooting and the atom striking the detector. Finally, Greer created a nanoscale 3D map of the Moon dust by reconstructing the data in three dimensions, using a color-coded point for each atom and molecule.
It’s the first time scientists have seen the type of atoms in a speck of lunar dirt, as well as their precise location. While APT is a well-known material science technique, it had never been used on lunar samples before. Other cosmochemists are encouraged to try it out, according to Greer and Heck.
“It’s great for comprehensively characterizing small volumes of precious samples,” Greer says. “We have these really exciting missions like Hayabusa2 and OSIRIS-REx returning to Earth soon uncrewed spacecrafts 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.”
Scientists can learn about one of our Solar System’s most critical forces by studying soil from the moon’s surface. With microscopic meteorites, streams of particles originating from the Sun, and radiation in the form of solar and cosmic rays, space is a harsh environment. While the Earth’s atmosphere shields us from space weathering, other bodies without atmospheres, such as the Moon and asteroids, do not.
As a result of space weathering, the soil on the Moon’s surface has changed, making it fundamentally different from the rock that makes up the rest of the Moon. It’s similar to a chocolate-dipped ice cream cone in that the outside doesn’t match the inside. In a way that no other technology can, APT allows scientists to examine for variations between space worn surfaces and unexposed lunar dirt.
They can better forecast what’s just beneath the surface of moons and asteroids that are too far away to bring to Earth if they understand the processes that cause these changes.
Greer’s original grain of lunar dust is still available for future investigations because she utilized a nanosized tip in her research. As a result, future generations of scientists will be able to make fresh discoveries and predictions based on the same priceless sample.
“Fifty years ago, no one anticipated that someone would ever analyze a sample with this technique, and only using a tiny bit of one grain,” Heck states. “Thousands of such grains could be on the glove of an astronaut, and it would be sufficient material for a big study.”
Greer and Heck emphasize the need for missions where astronauts bring back physical samples because of the variety of terrains in outer space.
“If you only analyze space weathering from the one place on the Moon, it’s like only analyzing weathering on Earth in one mountain range,” Greer says. “We need to go to other places and objects to understand space weathering in the same way we need to check out different places on Earth like the sand in deserts and outcrops in mountain ranges on Earth.”
“We don’t yet know what surprises we might find from space weathering. It’s important to understand these materials in the lab so we understand what we’re seeing when we look through a telescope,” Greer says.
“Because of something like this, we understand what the environment is like on the Moon. It goes way beyond what astronauts are able to tell us as they walk on the Moon. This little grain preserves millions of years of history.”
The findings persuaded NASA to pay the Field Museum, Northwestern University, and Purdue University for the next three years to analyze different types of lunar dust with APT to quantify its water content and investigate other elements of space weathering.
Funding for this work was provided by the TAWANI Foundation, the National Science Foundation, the Office of Naval Research, Northwestern University and the Field Museum’s Science and Scholarship Funding Committee.
