From the archive, originally posted by: [ spectre ]
SWEET SMELLING WELDING FUMES
Space Chronicles #4
By: ISS Science Officer Don Pettit
The Smell of Space
Few people have experienced traveling into space. Even fewer have
experienced the smell of space. Now this sounds strange, that a vacuum
could have a smell and that a human being could live to smell that
smell. It seems about as improbable as listening to sounds in space,
yet space has a definite smell. Being creatures of an atmosphere, we
can only smell space indirectly. Sort of like the way a pit viper
smells by waving its tongue in the air and thenpressing it to the roof
of its mouth where sensors process the molecules that have been
adsorbed onto the waggling appendage. I had the pleasure of operating
the airlock for two of my crewmates while they went on several space
walks. Each time, when I repressed the airlock, opened the hatch and
welcomed two tired workers inside, a peculiar odor tickled my
olfactory senses. At first I couldn’t quite place it. It must have
come from the air ducts that re-pressed the compartment. Then I
noticed that this smell was on their suit, helmet, gloves, and tools.
It was more pronounced on fabrics than on metal or plastic surfaces.
It is hard to describe this smell; it is definitely not the olfactory
equivalent to describing the palette sensations of some new food as
“tastes like chicken.” The best description I can come up with is
metallic; a rather pleasant sweet metallic sensation. It reminded me
of my college summers where I labored for many hours with an arc
welding torch repairing heavy equipment for a small logging outfit. It
reminded me of pleasant sweet smelling welding fumes. That is the
smell of space.
Anousheh Ansari Space Blog
“The docking process takes a long time. After docking, a leak check is
done for the docking hatch area to make sure there is no
depressurization. It usually takes close to two hours. I kept dozing
in and out as Mike and Misha went through the docking procedure.
The time went by really slowly, but finally the moment arrived and
they were ready to open the hatch. Mike and Misha called me closer and
told me to take a good whiff because this would be the first time I
would smell “SPACE.”
They said it is a very unique smell. As they pulled the hatch open on
the Soyuz side, I smelled “SPACE.” It was strange… kind of like burned
almond cookie. I said to them, “It smells like cooking” and they both
looked at me like I was crazy and exclaimed:”Cooking!”
I said, “Yes… sort of like something is burning… I don’t know it is
hard to explain…” ”
Sounds Like Ozone
by eldavojohn on Wednesday February 13, @10:17AM
When I was younger, I also arc wielded to fix various metal things
around farms. I too noticed this sweet, metallic smell.
When I was a teenager I read a lot of short stories. Especially all
the sci-fi & horror ones like Ray Bradbury, Philip K. Dick or Stephen
King. I don’t recall which one it was but a character had a train set
that had a short in it on the tracks. The arcing electricity would
give off this same smell. I learned through this short story that this
is an incidental way to produce ozone (O3) [wikipedia.org], a
greenhouse gas. And that the smell is in fact a low amount of ozone.
Perhaps you’ve detected it at the dentists office or while operating
an engine? From the Wikipedia entry:
Ozone may be formed from O2 by electrical discharges and by action of
high energy electromagnetic radiation. Certain electrical equipment
generate significant levels of ozone. This is especially true of
devices using high voltages, such as ionic air purifiers, laser
printers, photocopiers, and arc welders. Electric motors using brushes
can generate ozone from repeated sparking inside the unit. Large
motors that use brushes, such as those used by elevators or hydraulic
pumps, will generate more ozone than smaller motors.
I hope he doesn’t write himself off as crazy if he did detect ozone.
Or at least investigate where it could have come from. If there’s tiny
molecules of ozone floating around in orbit of the earth, I’m certain
that would be scientifically interesting. Perhaps he should test the
properties of these materials when exposed to ozone, do they attract
the molecules? Or perhaps he should put the materials in a vacuum here
on earth for a bit and then pull them out and see if he detects the
The human nose can be an extremely strong tool for some individuals,
perhaps this is more than just psychosomatic? It would drive me crazy
to never investigate this if I were in his shoes. It may seem trivial
but sometimes a peculiar notion is what drives scientists make a novel
discovery … or waste lots and lots of time.
PREVIOUSLY ON SPECTRE — THE SMELL OF MOONDUST
BY Tony Phillips
“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
Feel it-it’s soft like snow, yet strangely abrasive.
Taste it-“not half bad,” according to Apollo 16 astronaut John Young.
Sniff it-“it smells like spent gunpowder,” says Cernan.
How do you sniff 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.
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.”
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
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.
“The moon is like a 4-billion-year-old desert,” he says. “It’s
incredibly dry. When moondust comes in contact with moist air in a
lunar module, you get the ‘desert rain’ effect–and some lovely
odors.” (For the record, he counts gunpowder as a lovely odor.)
Gary Lofgren has a related idea: “The gases ‘evaporating’ from the
moondust might come from the solar wind.” Unlike Earth, he explains,
the moon is exposed to the hot wind of hydrogen, helium and other ions
blowing away from the sun. These ions hit the moon’s surface and get
caught in the dust.
It’s a fragile situation. “The ions are easily dislodged by footsteps
or dustbrushes, and they would be evaporated by contact with warm air
inside the lunar module. Solar wind ions mingling with the cabin’s
atmosphere would produce who-knows-what odors.”
Want to smell the solar wind? Go to the moon.
Schmitt offers yet another idea: The smell, and his reaction to it,
could be a sign that moondust is chemically active.
“Consider how moondust is formed,” he says. “Meteoroids hit the moon,
reducing rocks to jagged dust. It’s a process of hammering and
smashing.” Broken molecules in the dust have “dangling bonds”
–unsatisfied electrical connections that need atomic partners.
Inhale some moondust and what happens? The dangling bonds seek
partners in the membranes of your nose. You get congested. You report
strange odors. Later, when the all the bonds are partnered-up, these
Another possibility is that moondust “burns” in the lunar lander’s
oxygen atmosphere. “Oxygen is very reactive,” notes Lofgren, “and
would readily combine with the dangling chemical bonds of the moondust.”
The process, called oxidation, is akin to burning. Although it happens too
slowly for smoke or flames, the oxidation of moondust might produce an
aroma like burnt gunpowder. (Note: Burnt and unburnt gunpowder do not
smell the same. Apollo astronauts were specific. Moondust smells like
Curiously, back on Earth, moondust has no smell. There are hundreds of
pounds of moondust at the Lunar Sample Lab in Houston. There, Lofgren
has held dusty moon rocks with his own hands. He’s sniffed the rocks,
sniffed the air, sniffed his hands. “It does not smell like gunpowder,” he says.
Were the Apollo crews imagining things? No. Lofgren and others have a
Moondust on Earth has been “pacified.” All of the samples brought back
by Apollo astronauts have been in contact with moist, oxygen-rich air.
Any smelly chemical reactions (or evaporations) ended long ago.
This wasn’t supposed to happen. Astronauts took special “thermos”
containers to the moon to hold the samples in vacuum. But the jagged
edges of the dust unexpectedly cut the seals of the containers,
allowing oxygen and water vapor to sneak in during the 3-day trip back
to Earth. No one can say how much the dust was altered by that
Schmitt believes “we need to study the dust in situ–on the moon.”
Only there can we fully discover its properties: Why does it smell? How
does it react with landers, rovers and habitats? What surprises await?
NASA plans to send people back to the moon in 2018, and they’ll stay
much longer than Apollo astronauts did. The next generation will have
more time and better tools to tackle the mystery.