Finding Energy in the Moon

Using an exquisitely sensitive microscope, researchers have found tiny balloons of helium in lunar samples from Apollo 17.

 

   

Finding Energy in the Moon

Using an exquisitely sensitive microscope, researchers have found tiny balloons of helium in lunar samples from Apollo 17.

The moon as seen from Apollo 11, the first mission to land humans on the lunar surface, in 1969. (Photo: NASA)

 

By Katherine Wright

For decades there have been whispers of mining the moon’s energy-rich resources. Now researchers at the Naval Research Laboratory in Washington D.C. have taken a step toward this possibility, directly detecting one such resource—helium-3—in lunar rocks for the first time.

Exposed to the harsh environment of deep space, the moon’s surface is constantly bombarded by cosmic and solar radiation.  The radiation impacts so violently that it penetrates the soils—rock dust fragments—that cover most of the moon, and gets stuck inside the rock. One of these elements is helium-3, which originates from the sun, and could be shipped back to Earth for use as an energy source, or might even be used to power lunar nuclear fusion reactors. For this, scientists would need to work out how to efficiently extract the captured helium from the rocks. (Nuclear fusion would also need to become a viable energy-producing technology, which it isn’t yet, but that’s a different story.)

Helium-3 was first detected in lunar soils shortly after Neil Armstrong and Buzz Aldrin returned with samples from the first manned mission to the moon in 1969. Smashing the soil fragments into an even finer powder and then baking at temperatures hotter than those used in steel blast furnaces, scientists spotted helium-3 in the released vapors, suggesting that the element had come from inside the lunar samples. But exactly where and how it had been trapped was a mystery.

To solve this mystery, scientists needed to be able to look inside the lunar soil grains, which are typically smaller than the width of a human hair, image single atoms within this grain, and then chemically distinguish each atom from its neighbors. Not an easy feat. It’s only recently that technology has advanced far enough for scientists to do this.

Using the latest transmission electron microscope, which has sub-atomic resolution, Kate Burgess,  a scientist at NRL, has been imaging slices of soil grains collected during the Apollo 17 mission—the last manned mission to the moon. This kind of microscope shoots electrons through an object and measures how they get deflected. An electron “camera” captures the image this creates. In addition, the microscope Burgess uses has detectors that record how much energy the electrons lose as they pass through an individual atom and any X-rays the atom emits during this process. The exact energy loss and pattern of emitted X-rays are unique for each atom and how it is bonded to its neighbors, so these two signals can be used as atomic fingerprints. This allows Burgess to build up a map of the different atoms the rock sample contains, as well as taking electron photographs.

Dark blobs on the surface of a grain of  a lunar mineral called ilmenite turned out to be tiny balloons of helium. The blobs are just 10 nanometers in size, about a thousand times smaller than the width of a human hair. (Photo: Lunar and Planetary Science)

Burgess has been studying two lunar minerals—ilmenite and chromite—commonly found on the moon. While scanning the electron beam over a section of one ilmenite grain, she spotted dark blobs near the grain’s outer surface—they look like tiny balloons embedded in the rock—that appeared to be made of something different from ilmenite’s minerals (iron, titanium, and oxygen). Zooming in on one of the nanometer-sized dots—the technical term is vesicle—to study it more closely, Burgess picked up a helium signal in the elemental map. These were miniscule helium balloons.

Bradley De Gregorio and Kate Burgess, scientists at the Naval Research Laboratory.

“This is the first time [helium] had really been measured inside the sample,” said Burgess. She presented the results at the 48th Lunar and Planetary Science Conference, which took place in Texas at the end of March. “It is helium that was implanted while it was on the surface of the moon and then it’s still there,” she said.

Burgess and her colleagues, led by Rhonda Stroud, are part of the NASA-funded RIS4E research project.  Their work falls under the project’s Theme 4, which aims to maximize the amount of information can be gained from samples returned from the moon, asteroids or Mars.

Burgess also imaged chromite samples.  That mineral, too, is known to house helium, but she found no vesicles. “Kate’s data show that the helium goes into different locations depending on the mineral [type],” said  Stroud, who  is the head of the nanoscale materials research group at the Naval Research Laboratory (NRL) “It really seems to depend on the atomic structure of the material.”

Knowing exactly where helium is stored in different rocks means that scientists can devise processes for extracting the element. For ilmenite, this could be as simple as bursting the balloons. “If you sanded or crushed the top surface of ilmenite grains you would extract a large fraction of the helium because it’s in those bubbles, and you just break the bubbles and out comes the helium,” Stroud said. “You wouldn’t have to apply any heat.”

“There’s something special about ilmenite,” said Bradley De Gregorio, who also works with Burgess at NRL. “The chromite had no vesicles, but it had a little bit of helium in its structure, but not in any well resolved location.”  The team plans to do more studies to work out exactly what it is about the structures of ilmenite and chromite that allows one to store helium in bubbles, with the other doesn’t.

“Then maybe we can design a material that we can just fly on a spacecraft and collect helium [from space],” said De Gregorio. “A big helium collector, a helium farm, and bring that to Earth.”

Rhonda Stroud (foreground), Kate Burgess and colleagues work with the transmission electron microscope. (Photo: Naval Research Laboratory)

The moon as seen from Apollo 11, the first mission to land humans on the lunar surface, in 1969. (Photo: NASA)

 

By Katherine Wright

For decades there have been whispers of mining the moon’s energy-rich resources. Now researchers at the Naval Research Laboratory in Washington D.C. have taken a step toward this possibility, directly detecting one such resource—helium-3—in lunar rocks for the first time.

Exposed to the harsh environment of deep space, the moon’s surface is constantly bombarded by cosmic and solar radiation.  The radiation impacts so violently that it penetrates the soils—rock dust fragments—that cover most of the moon, and gets stuck inside the rock. One of these elements is helium-3, which originates from the sun, and could be shipped back to Earth for use as an energy source, or might even be used to power lunar nuclear fusion reactors. For this, scientists would need to work out how to efficiently extract the captured helium from the rocks. (Nuclear fusion would also need to become a viable energy-producing technology, which it isn’t yet, but that’s a different story.)

Helium-3 was first detected in lunar soils shortly after Neil Armstrong and Buzz Aldrin returned with samples from the first manned mission to the moon in 1969. Smashing the soil fragments into an even finer powder and then baking at temperatures hotter than those used in steel blast furnaces, scientists spotted helium-3 in the released vapors, suggesting that the element had come from inside the lunar samples. But exactly where and how it had been trapped was a mystery.

To solve this mystery, scientists needed to be able to look inside the lunar soil grains, which are typically smaller than the width of a human hair, image single atoms within this grain, and then chemically distinguish each atom from its neighbors. Not an easy feat. It’s only recently that technology has advanced far enough for scientists to do this.

Using the latest transmission electron microscope, which has sub-atomic resolution, Kate Burgess,  a scientist at NRL, has been imaging slices of soil grains collected during the Apollo 17 mission—the last manned mission to the moon. This kind of microscope shoots electrons through an object and measures how they get deflected. An electron “camera” captures the image this creates. In addition, the microscope Burgess uses has detectors that record how much energy the electrons lose as they pass through an individual atom and any X-rays the atom emits during this process. The exact energy loss and pattern of emitted X-rays are unique for each atom and how it is bonded to its neighbors, so these two signals can be used as atomic fingerprints. This allows Burgess to build up a map of the different atoms the rock sample contains, as well as taking electron photographs.

Dark blobs on the surface of a grain of  a lunar mineral called ilmenite turned out to be tiny balloons of helium. The blobs are just 10 nanometers in size, about a thousand times smaller than the width of a human hair. (Photo: Lunar and Planetary Science)

Burgess has been studying two lunar minerals—ilmenite and chromite—commonly found on the moon. While scanning the electron beam over a section of one ilmenite grain, she spotted dark blobs near the grain’s outer surface—they look like tiny balloons embedded in the rock—that appeared to be made of something different from ilmenite’s minerals (iron, titanium, and oxygen). Zooming in on one of the nanometer-sized dots—the technical term is vesicle—to study it more closely, Burgess picked up a helium signal in the elemental map. These were miniscule helium balloons.

Bradley De Gregorio and Kate Burgess, scientists at the Naval Research Laboratory.

“This is the first time [helium] had really been measured inside the sample,” said Burgess. She presented the results at the 48th Lunar and Planetary Science Conference, which took place in Texas at the end of March. “It is helium that was implanted while it was on the surface of the moon and then it’s still there,” she said.

Burgess and her colleagues, led by Rhonda Stroud, are part of the NASA-funded RIS4E research project.  Their work falls under the project’s Theme 4, which aims to maximize the amount of information can be gained from samples returned from the moon, asteroids or Mars.

Burgess also imaged chromite samples.  That mineral, too, is known to house helium, but she found no vesicles. “Kate’s data show that the helium goes into different locations depending on the mineral [type],” said  Stroud, who  is the head of the nanoscale materials research group at the Naval Research Laboratory (NRL) “It really seems to depend on the atomic structure of the material.”

Knowing exactly where helium is stored in different rocks means that scientists can devise processes for extracting the element. For ilmenite, this could be as simple as bursting the balloons. “If you sanded or crushed the top surface of ilmenite grains you would extract a large fraction of the helium because it’s in those bubbles, and you just break the bubbles and out comes the helium,” Stroud said. “You wouldn’t have to apply any heat.”

“There’s something special about ilmenite,” said Bradley De Gregorio, who also works with Burgess at NRL. “The chromite had no vesicles, but it had a little bit of helium in its structure, but not in any well resolved location.”  The team plans to do more studies to work out exactly what it is about the structures of ilmenite and chromite that allows one to store helium in bubbles, with the other doesn’t.

“Then maybe we can design a material that we can just fly on a spacecraft and collect helium [from space],” said De Gregorio. “A big helium collector, a helium farm, and bring that to Earth.”

Rhonda Stroud (foreground), Kate Burgess and colleagues work with the transmission electron microscope. (Photo: Naval Research Laboratory)