"New" data from the Moon landings, 40 years on
Using data that NASA thought it had lost, a lone scientist has determined why ...
One of the big unknowns during man's journey to the Moon was what would happen when we actually landed. The exact nature of lunar dust was a mystery that wasn't fully resolved until the Apollo 11 moon landing. Over the course of the six moon landings, NASA - and the rest of humanity - learned that moon dust is sticky, and would attach itself to spacesuits, equipment, and spacecraft alike.
A new study set to appear in an upcoming issue of Geophysical Research
looks at the nature of why moon dust attaches to
everything. The study found that the sun and the time of day on the
moon play a key role in its adhesion. Brian O'Brien, the
author of the paper, found that lunar dust's stickiness is a balancing act between electrostatic attraction and the
weak lunar gravity.
Over the course of a 710 hour lunar day, the Sun's position on the horizon changes, and the amount of ionizing radiation reaching the surface of the moon changes accordingly. In the early hours of the lunar day, the radiation manages to generate an electrostatic charge on individual dust particles - these average only 70 microns in diameter, so it does not take much charge to enable them to overcome the weak force of lunar gravity. Once the Sun reaches a certain position, the downward pull of lunar gravity takes over, and the dust falls off a surface.
An interesting study in its own right (who doesn't like drawing freebody diagrams of small particles?), it is made all the more interesting because the data used for it was "lost." The experimental data came from a pair of Dust Detector Experiments left on the lunar surface by Apollo 11 and 12 in 1969. O'Brien has a long history with lunar dust; 29 years ago, he published a paper that claimed the official NASA report on the failure of a lunar seismometer after only three weeks was incorrect. He contended that lunar dust kicked up from the launch of the ascent stage of Apollo 11 caused the device - the first ever placed by humans on another celestial body - to overheat.
Fast forward to late 2006. O'Brien learned from NASA's website that it had lost the tapes that contained the data from these dust experiments. NASA considered the tapes lost to time, but, thanks to his earlier work, O'Brien had his own set of 173 data tapes. Using printouts from 1969 and 1970, O'Brien revisited his earlier results (examining some for the first time) and used them to conclude that a balance between competing forces control the stickiness of lunar dust.
After deducing the mechanics behind lunar dust's properties, O'Brien offered a solution for future lunar missions. A simple "wide sun-proof shed, to block the rays that enhance dust's adhesive forces," O'Brien suggested. "Getting closer to understanding the physics of the lunar dust problems means moving one giant step towards management of the hazards."
Geophysical Research Letters, 2009. DOI: 10.1029/2008GL037116 (not yet active)