Coping with a lunar dust-up

CLEVELAND — Of all the hazards humans face in returning to the moon, one of the biggest may be the smallest: flecks of lunar dust far tinier than the period at the end of this sentence.

They blanket the orb's craggy surface with a powdery coating several inches thick. The moon is one vast desert of dust.

Though the Apollo astronauts ventured outside for only a few hours at a time, the clingy dust quickly dimmed their snow-white spacesuits to Pigpen gray. It got on their skin, in their eyes and up their noses, giving Apollo 17 lunar-module pilot Harrison Schmitt a temporary case of "lunar-dust hay fever."

Always in the way

The pervasive crud gummed up mechanical joints and coated the radiators on the lunar rover, causing its batteries to overheat.

It sneaked into oxygen-hose connections, snagged zippers and clotted Velcro fasteners. Scaling the ladder of the lunar lander with dust caked in his boot treads, Neil Armstrong almost made one small slip for mankind.

There was so much dust that, on Apollo 16, the cabin vacuum cleaner that was supposed to suck it up choked and died instead.

And the stuff wasn't soft, like lint. It had sharp, glassy edges that scratched helmet visors and camera lenses.

The Apollo 12 astronauts discovered that tramping around in the abrasive dust had worn away the outer layer of their spacesuits in several spots, exposing the insulation underneath.

The grit had gotten into the seals around their helmets and gloves, causing them to bleed oxygen. After two four-hour stints on the surface, Pete Conrad's suit was so close to the leak safety margin that he probably wouldn't have been allowed outside again had a third excursion been planned.

Focus of research

As NASA prepares to send crews back to the moon by 2020, with eventual six-month stays compared with the three-day Apollo sorties, mission planners have dust on their minds.

Researchers at NASA centers are studying why lunar dust behaves the way it does, whether it's toxic and how it might be controlled.

Much of the basic work is under way in Cleveland's Glenn Research Center labs. One approach mimics the extreme conditions on the moon's surface that give the dust its unique properties. Another involves a sandbox the size of a volleyball court where engineers test the traction of prototype lunar buggies.

But to aim for the future, NASA first had to look back — to the surprising Apollo experience with dust nearly four decades ago, and then much deeper into the past, to the formation of the dust itself over the past 4.5 billion years.

Without an atmosphere, the moon lacks liquid water and wind, the forces of erosion on Earth. But meteorite strikes have filled that void, relentlessly pummeling lunar rocks into the fine, talcum-like grains that cover the surface today.

Other powers are at work to further disrupt the dust. Tiny micrometeorites regularly ping the moon's face at more than 60,000 mph — enough energy to melt or partially vaporize dust particles and change their chemical makeup.

The melting welds individual grains into flea-sized chunks called agglutinates. Their glassy, jagged edges give the dust its abrasiveness and help it stick to stuff.

Wild electrons

Most of its clingy-ness, however, is due to static electricity, the same pesky mechanism that mates socks with sweaters in the dryer.

On the moon's "day" side, X-ray and ultraviolet radiation beaming in from the sun blast away electrons from the dust grains, leaving them with a positive charge.

Some NASA scientists think the repulsing forces between these like-charged dust particles are strong enough to shoot the lightest grains 60 miles or more above the moon's surface. They speculate the dust regularly rises and falls, like water droplets in a fountain, although the specks would be too small to see.

By the same theory, dust fountains should erupt on the moon's night side, too, but oppositely charged ones. Without sunlight's positive influence, the dusty surface acquires a negative buildup from electrons delivered by the solar wind — a gale of high-energy particles billowing out from the sun.

At the tumultuous divide between dark and light — a twilight zone called the terminator that marches across the surface as the moon rotates — the shifting electric fields may shove the dust sideways, scattering it greater distances.

Though this idea of "dynamic," fountaining dust is new, it is based in part on observations Apollo astronauts made more than 30 years ago.

NASA scientists had figured the actions that stir up the most lunar dust were localized, human-caused ones: spacecraft landing and blasting off, rovers skidding around, astronauts stomping and jumping and, in the future, construction machinery digging and scooping as a moon base takes shape.

Now, the dust-busters may have to plan for the moon's own dust-churning processes too.

"That's another thing we're attempting to address," said Mark Hyatt, a researcher at the Glenn center. "What's the magnitude of the effect, and do we have to design for it because we're going to be there for such a long period of time?"

Whether dust clouds are kicked up by astronaut boots or the sweep of the terminator, the outcome is the same: It sticks to everything.