[asa] moon dust

Since the moon dust argument is so popular, I thought it might be
helpful to post what I recently found in tracking down details.

The material on the moon's surface (or other planets) above the solid
rock is called regolith. As on Earth, it includes smaller and larger
pieces and is more solidly compacted below the surface. The claim
that the dust layer on the moon is very thin was based on a newspaper
photo of astronaut footprints. In reality, the astronauts were able
to hammer a hand core in 70 cm and mechanical drills went in over a
meter without reaching solid rock. Based on measurements by
seismometers and observation of shallow craters (no old small craters
are visible; young small craters appear to only penetrate the
regolith), average depth of regolith is estimated at about 4 m. Thus,
the claim that the layer is only a few cm or inches is off by a
similar order of magnitude to some of the high estimates for dust
layer thickness that are popularly cited in young-earth arguments.
(The presence of other, lower estimates for expected regolith
thickness is not usually mentioned.)

If you step on dust, on Earth or the Moon, you don't sink to solid rock.

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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