The Mysterious Smell of Moondust
Every Apollo astronaut did it. They couldn't touch their noses to the lunar surface. But, after every moonwalk (or "EVA"), they would tramp the stuff back inside the lander. Moondust was incredibly clingy, sticking to boots, gloves and other exposed surfaces. No matter how hard they tried to brush their suits before re-entering the cabin, some dust (and sometimes a lot of dust) made its way inside.
At the end of a long day on the moon, Apollo 17 astronaut Gene Cernan rests inside the lunar module Challenger. Note the smudges of dust on his longjohns and forehead. Photo credit: Jack Schmitt.
Once their helmets and gloves were off, the astronauts could feel, smell and even taste the moon.
The experience gave Apollo 17 astronaut Jack Schmitt history's first recorded case of extraterrestrial hay fever. "It's come on pretty fast," he radioed Houston with a congested voice. Years later he recalls, "When I took my helmet off after the first EVA, I had a significant reaction to the dust. My turbinates (cartilage plates in the walls of the nasal chambers) became swollen."
Hours later, the sensation faded. "It was there again after the second and third EVAs, but at much lower levels. I think I was developing some immunity to it."
|Moondust. "I wish I could send you some," says Apollo 17 astronaut Gene Cernan. Just a thimbleful scooped fresh off the lunar surface. "It's amazing stuff."
Other astronauts didn't get the hay fever. Or, at least, "they didn't admit it," laughs Schmitt. "Pilots think if they confess their symptoms, they'll be grounded." Unlike the other astronauts, Schmitt didn't have a test pilot background. He was a geologist and readily admitted to sniffles.
Schmitt says he has sensitive turbinates: "The petrochemicals in Houston used to drive me crazy, and I have to watch out for cigarette smoke." That's why, he believes, other astronauts reacted much less than he did.
But they did react: "It is really a strong smell," radioed Apollo 16 pilot Charlie Duke. "It has that taste -- to me, [of] gunpowder -- and the smell of gunpowder, too." On the next mission, Apollo 17, Gene Cernan remarked, "smells like someone just fired a carbine in here."
Schmitt says, "All of the Apollo astronauts were used to handling guns." So when they said 'moondust smells like burnt gunpowder,' they knew what they were talking about.
To be clear, moondust and gunpowder are not the same thing. Modern smokeless gunpowder is a mixture of nitrocellulose (C6H8(NO2)2O5) and nitroglycerin (C3H5N3O9). These are flammable organic molecules "not found in lunar soil," says Gary Lofgren of the Lunar Sample Laboratory at NASA's Johnson Space Center. Hold a match to moondust--nothing happens, at least, nothing explosive.
What is moondust made of? Almost half is silicon dioxide glass created by meteoroids hitting the moon. These impacts, which have been going on for billions of years, fuse topsoil into glass and shatter the same into tiny pieces. Moondust is also rich in iron, calcium and magnesium bound up in minerals such as olivine and pyroxene. It's nothing like gunpowder.
So why the smell? No one knows.
ISS astronaut Don Pettit, who has never been to the moon but has an interest in space smells, offers one possibility:
"Picture yourself in a desert on Earth," he says. "What do you smell? Nothing, until it rains. The air is suddenly filled with sweet, peaty odors." Water evaporating from the ground carries molecules to your nose that have been trapped in dry soil for months.
Maybe something similar happens on the moon.
Story continues at physorg.com