Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Solar panels "Bright new star" ?
Date: Sat, 2 Dec 2000 18:21:55 GMT

In article <V8aW5.38481$nh5.2627402@newsread1.prod.itd.earthlink.net>,
John M. Darnielle <johndarnielle@earthlink.net> wrote:
>  The Moon looks pretty bright even
>> though its surface is actually as black as coal (!)...
>
>Huh? I've seen coal, and I've seen lunar rocks, and I'm sure that one was
>black and one was grey (dark grey to light grey, but grey)

You've seen *cleaned* lunar rocks.  Here's what Don Wilhelms (a planetary
geologist) had to say about the opening of the Apollo 11 sample boxes, in
his "To A Rocky Moon":

  After what seemed like an eternity, the first box was opened at 3:49 PM.
  Then the first Teflon bag was slit open.  All eyes focused on what looked
  like: the Rosetta Stone? primordial chondrites? sparkling pegmatites?
  No; dirty coal.  Astronomers had been saying that the Moon is really dark
  and not off-white as it seems in the night sky, and obviously they were
  right...

The appearance of those first rocks has also been compared to badly burnt
potatoes.

>My understanding
>is that the moon is as bright as it is because of the high concentration of
>titanium dioxide in it's soil, the same pigment that makes white paint
>white.

While there is a bit more titanium dioxide than is usual on Earth, it's
not in the highly-purified form used in paint.  The *brightest* lunar
soils reflect less than 25% of the light that hits them, and 5-10% is more
typical.

>...I just don't see how the moon's surfuce can be as "black as coal".

As I noted before, consider that when the Moon -- an object in bright
sunlight! -- is in the daylight sky, it's dim to the point of being almost
invisible.  Even coal will look bright if it's brilliantly lit against an
absolutely dark background.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)