Thursday, November 21, 2013

Apollo 12 ALSEP first to measure dust accumulation

Apollo 12 ALSEP Central Station
Apollo 12 ALSEP, Central Station, with DTREM (Lunar Dust Collector) marked with arrow. Alan J. Bean, EVA-1;  Oceanus Procellarum, November 19, 1969 (AS12-47-6927) [NASA/JSC/ALSJ].
A dataset thought to have been lost, from an ingenious experiment deployed on the Moon by Apollo astronauts more than four decades ago, has been rediscovered and analyzed. As a result, the Lunar Dust Collector deployed as integral to the Apollo 12 ALSEP system, has become the first instrument to record a measurable rate of dust accumulation on the lunar surface. 

The news is timely, of course, coming the beginning of the Lunar Atmosphere and Dust Environment Explorer (LADEE) science mission, and arriving on November 19, the 44th anniversary of the Apollo 12 expedition.

Keith Cowing (LOIRP)

The Lunar Dust Detector, attached to the corner of (the ALSEP Central Station, pictured above), left by the Apollo 12 astronauts, made the first measurement of lunar dust accumulation. As the matchbox-sized device's three solar panels became covered by dust, the voltage they produced dropped.

When Neil Armstrong took humanity's first otherworldly steps in 1969, he didn't know what a nuisance the lunar soil beneath his feet would prove to be. The scratchy dust clung to everything it touched, causing scientific instruments to overheat and, for Apollo 17 astronaut Harrison Schmitt, a sort of lunar dust hay fever. The annoying particles even prompted a scientific experiment to figure out how fast they collect, but NASA's data got lost.

Retrieving a surface sample behind boulders on a crater rim at Apollo 17 Science Station 5, Taurus Littrow valley; December 12, 1972 - Lunar module pilot and geologist Harrison Schmitt already carries a substantial sampling of abrasive, fine lunar dust on his moon suit. Schmitt endorsed development of 'dust mitigation' technology as a high priority for program planners prior to establishing 'extended human activity' on the Moon (Eugene Cernan - AS17-145-22157) [NASA/JSC/ALSJ].
Or, so NASA thought. Now, more than 40 years later, scientists have used the rediscovered data to make the first determination of how fast lunar dust accumulates. It builds up unbelievably slowly by the standards of any Earth-bound housekeeper, their calculations show -- just fast enough to form a layer about a millimeter (0.04 inch) thick every 1,000 years. Yet, that rate is 10 times previous estimates. It's also more than speedy enough to pose a serious problem for the solar cells that serve as critical power sources for space exploration missions.

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