Looking up at the moon, you might
think that it’s relatively benign, maybe a nice place to visit? Maybe you
wonder, as you stare at its cratered face as it drifts across the night sky,
why we haven’t been back since Apollo 17?
There may be a good reason for that. And it may come down to lunar regolith, or, moon dust. During the Apollo missions, the substance got everywhere, inside the lander, on the suits, beneath the fingernails of astronauts, in their eyes, in their lungs, caused equipment and computer failure, and most troubling, was how it wore down the protective layers of the astronaut’s suits over time. It also easily picks up an electrostatic charge (if it doesn’t already have one from the constant bombardment from charged particles from the solar wind). By the time they’d finished their mission and were ready to return home, the moon dust had worn their boots down to such a degree, that there was risk of a complete breach in some suits.
Lunar regolith is like sand, but since it’s constantly blasted by charged particles by the solar wind, it’s as fine as glass, and it carries a slight magnetic charge from constant exposure to the solar wind, meaning it sticks to everything. It covers nearly the entirety of the moon’s surface; bedrock is only visible on the walls of craters. Scientists believe that this moon dust was created by uncountable impacts from meteorites.
It was feared that the lunar dust would be too light to support the lunar lander’s weight at the beginning of the Apollo program. Fortunately, robotic Surveyors showed that the lunar surface was firm enough to support a landing spacecraft. Later, astronauts observed that the surface of the moon felt very “firm” beneath their feet.
With NASA’s current plans to return to the moon in the near future, the question becomes; how will they deal with the challenges that lunar regolith presents?
Well, it’s not just the moon that we’ll have to consider when it comes to that challenge. Mars, a source of constant fascination by people dreaming of humanity’s inevitable ascension to the stars, is covered in the stuff. Astronauts would be forced to contend with Mars’ dust just as the Apollo astronauts did, and what’s worse, is that they won’t have the benefit of being close to home if the dust manages to damage their suits, gets into their lungs, or the systems of their gear, landers, shelters, and other equipment.
It’s not just Mars, though. Any body in our solar system that doesn’t have a significant atmosphere and is exposed to the solar wind will also have regolith. This includes many of Jupiter’s moons, asteroids that we may wish to land on, etcetera.
Larry Taylor, a distinguished professor of planetary sciences at the University of Tennessee, has an idea about what we can do with regolith. He said this to hundreds of scientists at a recent Lunar Exploration Advisory Group (LEAG), “I am one of those weird people who likes to stick things in ordinary kitchen microwave ovens to see what happens.” In his home state of Tennessee, his most famous experiment involved a bar of Irish Springs soap, which quickly turned into “an abominable monster” when the microwave’s start button was hit.
The experiment described at LEAG involved the transformation of regolith: He once put a small sample of lunar soil brought back by Apollo astronauts into a microwave. Taylor found that it melted within 30 seconds, at only 250 watts.
And the reason why it melted so quickly has to do with moon dust’s composition. It’s produced from the constant bombardment of micrometeorites. As these micrometeorites slam into lunar sand and rocks at incredible velocities, they melt and form incredibly small glass shards. The glass contains nanometer-scale beads of pure iron—so-called “nanophase” iron. Those tiny iron beads efficiently concentrate microwave energy, causing the beads to “sinter,” or fuse the loose soils into large clumps.
Taylor’s observations have led him to imagine all sorts of machinery that could be sent to the Moon and then used to fuse lunar dust into useful solids.
He continues on this subject by saying, “Picture a buggy pulled behind a rover that is outfitted with a set of magnetrons.” (A magnetron is the heating element in a microwave oven.) “With the right power and microwave frequency, an astronaut could drive along, sintering the soil as he goes, making continuous brick down 0.6 meters deep.” He added that by changing the power settings the astronaut could melt the top inch or two of the soil to make a glass road.
“Or say that you want a radio telescope,” he continues. “Find a round crater and run a little microwave ‘lawnmower’ up and down the crater’s sides to sinter a smooth surface. Hang an antenna from the middle—voila, instant Arecibo!” Taylor is referring to a giant 305-meter diameter radio telescope formed from a natural circular valley in Puerto Rico.
Still, many technological challenges remain before Taylor’s ideas can be put to test. Sintering regolith in a microwave on Earth is completely different than doing it on the moon. For one, the moon has no atmosphere.
The idea has promise, however, using the Lunar surface to our advantage as we explore, creating landing pads, roads, building materials and even radiation shielding with this sintering technique. Taylor goes on to say, “The only limit, is imagination.”
But, even if sintering moon dust is viable, there remain other risks. Astronauts will have to land on the Lunar surface before any sintering can be done, and they will be exposed to moon dust when exploring the surface (even while using one of these proposed “microwave lawnmowers”).
And there are the potential adverse health effects of inhaling the stuff. Harrison Schmitt said (when he sniffed the air in his lunar module, the Challenger, stating that it smelled like gunpowder. His commander Gene Cernan agreed.
“The real problem is the lungs,” Russel Kerschmann, a pathologist at NASA Ames said. “In some ways, lunar dust resembles the silica dust on Earth that causes silicosis, a serious disease.”
Silicosis is formerly known as “stone-grinder’s disease,” which first came to wide public knowledge during the Great Depression when hundreds of miners in West Virginia died within five years of breathing the fine quartz dust kicked into the air by their drilling. And they had only been drilling for several months.
He goes on to say, “It was one of the biggest occupational health disasters in U.S. history.” To be clear, Kerschmann isn’t saying that this health condition will arise in astronauts who travel to the Moon, but it is a possibility.
Then there are the risks to machinery inside their lunar modules, vehicles, computers, and the suits themselves. Among ideas proposed for handling the problem include improved ventilation with magnetic filters, magnetic traps under floor grates, air showers, vacuum cleaners, dust covers, dust repellent, as well as magnetic “wall-paper,” and many more additional potential technologies.
What’s amazing about how we’re facing these challenges is that by solving them on the Moon, we may be paving the path to colonizing the rest of our solar system (other logistical and technological problems notwithstanding).