Magnetic Moondust

Taylor has since designed a prototype air filter with permanent magnets inside. "When the filter gets dirty, you pull the magnets out, and the dust falls into a box." A later design with electromagnets works more efficiently: "You pull the plug on the electromagnet, tap it, and the dust rains down into a container." He's now working on a prototype design for a "dust brush" using permanent magnets.

Earth dust is not magnetic, so why should moondust be?

"Moondust is strange stuff," explains Taylor. "Each little grain of moondust is coated with a layer of glass only a few hundred nanometers thick (1/100th the diameter of a human hair)." Taylor and colleagues have examined the coating through a microscope and found "millions of tiny specks of iron suspended in the glass like stars in the sky." Those iron specks are the source of the magnetism.

Researchers believe the glass is a by-product of bombardment. Tiny micrometeorites hit the surface of the moon, generating temperatures hotter than 2,000°C, literally the surface temperature of red stars. Such extreme heat vaporizes molecules in the melted soil. "The vapors consist of compounds such as FeO and SiO2," says Taylor. If the temperature is high enough, the molecules split into their atomic components: Si, Fe, O and so on. Later, when the vapors cool, the atoms recombine and condense on grains of moondust, depositing a layer of silicon dioxide (SiO2) glass peppered with tiny nuggets of pure iron (Fe).

A thin coating of iron isn't enough to make sand- or gravel-sized particles noticeably magnetic, any more than spraying a thin coating of iron on a heavy basketball would make it stick to a magnet, says Taylor. But a thin coating is plenty for particles smaller than about 20 microns. They have so little mass compared to their surface area, they're easily lifted by Taylor's magnets.

Magnets aren't the only way to deal with moondust. NASA is considering a whole suite of options from airlocks to vacuum cleaners. But, if Taylor is right, magnets will prove important, and astronauts won't find moondust so troublesome the next time around.

For more info, visit:

The Lunar Dust Problem: A Possible Remedy
http://www.lpi.usra.edu/meetings/resource2000/pdf/7004.pdf

Magnetic Properties of Apollo 17 Soil Sample 70051
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1945.pdf

Video: The Moon [FirstScience presents]
Since its formation 4.5 billion years ago the Moon has been edging away from Earth yet it has influenced our planet in many profound ways.