From: Ian Goddard (Ian@Goddard.net)
Date: Wed Feb 21 2001 - 19:43:52 MST
A question about this here (hick-up) moonshine...
One thing I notice as I review Appolo images is that the
lunar surface appears to have a specular-reflection effect
that causes some areas of lunar surface to reflect brighter
than other areas relative to sun & viewer positions (surface-
luminosity differential is also a function of ground slant).
Here's one of many examples (a panoramic 180-degree view):
http://www.hq.nasa.gov/office/pao/History/alsj/a11/a11.1093226_bm.jpg
The Effect: notice that the light is brightest in the middle
of the panorama and the shadows on either side point to that
bright area, ergo, the sun is directly behind the camera as
it faces that brighter area of the moon's surface. I believe
this effect causes a few of the so-called lighting "anomalies."
The Hypothesis: I believe this is a result of each dust particle
having a small area of specular reflection, or area of maximum
reflective luminosity, just like a round sphere has resting on
a table in a room with one light source. The location of this
bright area on the sphere depends on the observers's position
relative to the sphere and the light source. From one point of
view the bright area would be on the other side of the sphere,
which would thus appears dark from that position. So Apollo
images with a brighter area are where the camera is seeing the
bright areas on the millions of lunar surface-dust particle.
Supporting this lunar-reflectance hypothesis is this photo:
http://images.jsc.nasa.gov/images/pao/AS14/10075616.jpg
A strong specular solar reflection comes off the dust compressed
by the rover's wheels, check it out, quite an interesting effect!
The compression makes the dust surface uniform, like a shiny panel.
Here's an example of a specular-reflection effect coming of some
but not all the lunar hills (a good example of ground slant):
http://images.jsc.nasa.gov/images/pao/AS17/10075948.jpg
The Question: I believe I've heard what I've described above
before, but I cannot recall where and I haven't found anything
on the web pertaining to this feature of lunar-surface reflectance.
So (phew... finally to the question), anyone know more about this?
Would this effect itself constitute evidence of being on the moon
(as opposed to only being an effect that produces an "anomaly")?
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