Lunar soil smells like gunpowder. No, really. And it’s lethal.
When the Apollo missions first landed on the moon, the astronauts were concerned with the, then unknown, depth of the lunar soil. When they arrived, they found the soil to be a safe & comfortable quarter inch layer of very fine powder. What they didn’t expect was the many problems and hazards the dust caused.
What is moon dust anyway?
Moon dust is actually a collection of tiny rock chips and shards from meteor impacts. Since the moon has no atmosphere, meteors slam down at full speed, breaking up anything in their path.
The dust consists of microscopic, sharp edged grains are incredibly abrasive. There’s no wind or water to wear down these tiny knife edges. No weathering means perfect preservation of sharp edges.
Moon dust is chemically fairly simple, at least compared to earthly soil. Almost half is silicon dioxide glass created by meteoroids hitting the moon. These impacts create sudden high temperatures, fusing topsoil into glass. The newly formed glass is then flash-frozen by the vacuum of space, with the impact shattering it into microscopic pieces. Moon dust is also rich in iron, calcium and magnesium bound up in minerals such as olivine and pyroxene.
Put more simply, moon dust is mostly a pile of sharp broken glass.
Because of the lack of lunar atmosphere, and the friction created my meteor impacts, the soil also has a strong static charge.
What’s it like?
Astronauts reported a number of observations of the moon dust. From a transcript from the first moon walk on Apollo 11:
109:43:16 Aldrin: Beautiful view!
109:43:18 Armstrong: Isn’t that something! Magnificent sight out here.
109:43:24 Aldrin: Magnificent desolation. (Long Pause)
109:43:47 Aldrin: Looks like the secondary strut had a little thermal effects on it right here, Neil.
109:43:54 Armstrong: Yes. I noticed that. That seems to be the worst, although similar effects are all around.
109:44:07 Aldrin: (Garbled) very fine powder, isn’t it?
109:44:09 Armstrong: Isn’t it fine?
109:44:11 Aldrin: Right in this area I don’t think there’s much of any (garbled) fine powder some (garbled) clods together, and it’s hard to tell whether it’s a clod or a rock.
109:44:23 Armstrong: Notice how you can kick it out.
109:44:28 Aldrin: Yeah. And it bounces and then (garbled) (Pause) Reaching down is fairly
easy. (Garbled) get my suit dirty at this stage. (Pause)
Once back inside the lunar lander, astronauts would remove their helmets and get to examine the dust stuck on their suits. The dust would stick to everything it touched with a static charge. Space suits quickly became grey & dirty with the dust that just wouldn’t come off.
Several astronauts reported that lunar soil smells like burnt gunpowder. They were always specific- not just gunpowder, but burnt gunpowder.
They also reported that it felt soft like snow, yet strangely abrasive. Its texture was much like graphite, only with an abrasive static cling.
When describing the taste (since it did get everywhere), Apollo 16 astronaut John Young commented that it was “not half bad”.
Apollo 17’s Cernan later said in “Apollo 17 Soil Mechanics Investigation”:
“The dust was very difficult to work in and was a big hindrance. It obscured your vision if you let it get on your visor. It was almost like a dew or mist because it clung to everything. It got on every movable surface, it got in the suits, and when we got out of our suits in the spacecraft in between EVAs, it got in the pores of our skin and got under our fingernails. And it didn’t just get on the outside parts of our nails and get them dirty but, literally, it got down between the skin and the nail. It took three months for lunar dust to grow out from under my nails. It infiltrates.“
“I describe lunar dust as being like very, very fine graphite. But graphite is a lubricating material; this is not. This is just the opposite; it’s very abrasive. And it has a smell very few people, if any, have smelled on the Earth. It smells something like spent gunpowder; like you’ve just fired a shotgun or something and you can smell that powder. The dust made lunar operations half again more difficult than it would have been without the dust. It took time to dust ourselves off, to clean the equipment. I knocked a fender off and quickly found out that you can’t operate in a Rover vehicle without a fender because you throw dust all over.”
All this dust scattering around was bound to get into the lungs of the astronauts. Apollo 17 astronaut Jack Schmitt came down with a case of lunar hay fever- he was allergic to the dust. Apparently he was the only one, though astronauts are reluctant to report medical issues. (Would you report a runny nose if it meant forgoing a walk on the moon?)
OK, so it’s messy. Why is it dangerous?
The fine dust got into every seal, every spacesuit joint, and every moving part on the missions. Many of the astronauts found dust particles had jammed up the shoulder joints of their spacesuits. Moon dust got into the joints and wore down seals, causing the spacesuits to slowly leak air pressure.
Apollo astronauts often went through 2 pairs of gloves, after discovering the lunar dust grinding on glove locking rings, making them unsafe to use in the moon’s space-vacuum surface. Dust landing on helmet visors couldn’t be easily cleaned. Wiping it off would produce a large swath of scratches, fogging up the view. Imagine cleaning glass with sandpaper- only worse. The same went for cameras and any optical surface. Being million of miles from home in deep cold and vacuum and not being able to see where you’re going is not safe. The only solution they had was to use a small camera cleaning brush, which took time and was partially effective at best.
Soil that had been collected in air-tight flasks came back to earth in containers that were no longer air-tight. The soil had ground apart the seal, exposing it to earthly air and humidity. As a result, the “burnt gunpowder” smell wore off, and was not noticeable when the dust was examined on earth.
Long term health effects of lunar soil are not known. Earthly materials of “ultrafine” airborne particles are known to be hazardous, and in some cases cause cancer. (Can you say asbestos?) Some particles may be small enough to pass through the lungs and even the blood/brain barrier, potentially causing brain damage. More research is needed to be done to answer these questions.
Any future missions to the moon will have to have aggressive plans for dealing with this toxic abrasive. The Apollo missions were short enough a duration that the seals to the exit hatch were not greatly affected. Longer missions will need to plan for hatch failures, and related hazards. Apollo’s missions of a few days could afford having extra sets of gloves and slow spacesuits leaks. These annoyances would quickly become serious in an extended mission. Once you’re out of air, your options get pretty slim.