The
alien and perilous dust on the moon has prompted scientists to ponder lunar
health standards that would be set before astronauts go there again.
A
diverse team that includes flight surgeons, industry air quality experts, toxicologists,
lunar geologists, and even an astronaut is examining how harmful lunar dust
could be to humans.
"Lunar
dust is unlike
any kind of dust we're used to breathing on Earth," said Noreen Khan-Mayberry,
space toxicologist at NASA's Johnson Space Center in Houston, Texas.
She
and other members of the Lunar Airborne Dust Toxicity Advisory Group (LADTAG) have
some concerns about the toxicity of the chemically reactive lunar dust grains,
which also contain nano-particles of natural metal and glass shards formed from
a combination of chemical reactions, meteorite impacts and solar wind
bombardment.
LADTAG
will help NASA set health standards for astronaut exposure to the dust — a
necessary step for designing the spacecraft, rovers, and habitats that will
return humans to the moon.
When
the first Apollo astronauts stepped onto
the moon, one of the lesser problems they were expecting was dust. But they
soon found the gray stuff clogging up instruments and causing breathing and
vision problems inside the lunar lander.
Alan
Bean, Apollo 12 astronaut, noted that trying to brush the dust off only rubbed
it deeper into their spacesuits. That clinginess comes from both the barbed
shapes of lunar dust grains and an electrostatic charge built up by solar wind
exposure, because the moon lacks a protective magnetic field like the one that
shields Earth.
Lunar
dust consists of uneven rock grains too small for the human eye to see. The constant
bombardment from solar radiation has left them porous like "swiss cheese," said
John James, chief toxicologist for NASA at the Johnson Space Center and
co-chair of LADTAG.
The
grains range from spherical to highly angular shapes, remaining sharp and
unworn by any wind or other natural processes.
"It's
the glassy properties and jagged shape that create abrasiveness," James said,
adding that the "sandpaper" effect could damage spacecraft hardware and
spacesuits.
The
LADTAG team wants to examine how such an effect could similarly damage
sensitive human skin and eyes, Khan-Mayberry noted.
The
moon's near-vacuum environment also leaves lunar dust grains covered with chemically
reactive bonds which would normally become neutralized through interaction with
atmospheric gases such as oxygen. That means they might react in highly toxic
ways when breathed into the lungs, although scientists hope that the dust will become
less threatening in a lunar habitat after reacting with the indoor air.
LADTAG
researchers test such exposure in two ways. One method injects fluid mixed with
lunar dust into the lungs of an anesthetized lab mouse or rat, while another
method puts lab animals in cylinders containing lunar dust to watch them inhale
it normally.
The
second method better simulates how astronauts might breathe in lunar dust, but
it also requires more of the "finite" lunar dust supply brought back from the
moon, Khan-Mayberry said. The LADTAG team may eventually resort to grinding
down larger lunar dust samples to add to the supply.
Figuring
out the quirks and characteristics of lunar dust has proven a team-building
exercise that combines geological studies with medical knowledge.
"What's
really made this interesting is getting lunar geologists and toxicologists to
communicate," said James. "I think we're going to come up with some really
remarkable stuff from our interaction."
LADTAG
plans to present its findings to NASA around 2010, which will hopefully allow
the space agency to set health standards for astronauts who may work around
lunar dust. That would also push engineers to design habitats and rovers that
could keep
dust out, and maybe even put lunar
dust to good use.
However,
the group's work won't end there — members will tackle the next challenge of
Mars by reorganizing as MADTAG.
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