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In article <1cnihlINN59s@uwm.edu> wlee@csd4.csd.uwm.edu (Wan Ngai Wayne Lee) writes:
>   ... the astronauts passed through a "dead man's zone" during
>   which a descent stage failure could not be solved by using
>   the ascent stage to return to orbit...
>   a. Did this only apply to the early missions or did the "dead
>      man's zone" possibility apply to all of the moon shots?

All of them.  Such zones are also known as "black zones".  In the case of
the lunar landings, as far as I know there was only one:  a descent-stage
failure at very low altitude would not leave enough time for staging and
ascent-stage ignition before the crash.  As far as I know, if they could
get the ascent stage lit and if it stayed lit for a while, they always
had an abort procedure available (although some required CSM cooperation).

>   b. If the descent stage would have failed, would the procedure
>      have been for the astronauts to continue dropping to the
>      surface or attempt an abort to orbit?

Without the descent stage, landing was not possible.  The descent stage
carried the landing gear.  It also had the throttlable engine needed for
a soft landing.  (Making a rocket engine throttlable is not simple and
is done only when necessary; the ascent-stage engine was not throttlable.)
Even if you could land with the ascent stage, you wouldn't have the fuel
to return thereafter.

>   During the Apollo missions, was it ever possible for Earth-based
>   radar to determine where moon-orbiting craft were?  It is my
>   impression that the answer was no...

Wrong, in fact very wrong.  All the precision navigation was done by
Earth-based tracking.  However, this tracking did rely heavily on the
transponders (which, speaking sloppily, basically amplify the received
signal and retransmit it) carried by the spacecraft.  "Skin tracking" --
tracking an uncooperative object by its radar reflection -- was not
practical for objects of that size at that distance, and still isn't.

>   Has the prehistoric "flip" of Earth's magnetic field been proven?

It's about as well proven as it can be, although the geologists are
still arguing about details.

>   What may cause this in the future?

It seems to happen periodically.  Just how quickly it happens, and
whether it is spontaneous or triggered by something, is unclear.

>   Does the Moon has its own magnetic field?  If I had a compass on
>   the moon, how would it behave?

The Moon's magnetic field is feeble and confused.  A compass would not
be useful.

>   In the 1970's, I read that Apollo 12 & 14 ALSEP sensors (ION) picked
>   up what seemed to be a water vapor emission near Fra Mauro.  What
>   would be an alternative explanation for such readings?

Nobody seriously doubts that the Moon still outgasses a little here
and there.  Whether substantial deposits of volatiles still exist in
reachable places is another question.

>   How respectable is the notion that frozen water may exist on the moon
>   and how would such a discovery related to moon's origin & history? 

Very respectable, but it would have to have arrived after the Moon's
formation and early volcanic period.  There is considerable suspicion
that volatiles deposited on the Moon by comet impact may still exist,
frozen in polar craters which never get direct sunlight.  Suspicions
have been strengthened considerably of late because radar mapping has
discovered what is probably ice at the poles of Mercury (!).  Flying
a gamma-ray spectrometer in low lunar polar orbit, which would (among
other things) let us survey the entire Moon for near-surface ice, is
a very high priority for lunar scientists.

>   By the way, Arthur C Clarke has put moon water in his 2061 novel.

Lunar water, either as fossil ice or water of hydration, has been a
staple of science fiction for a long time.  It came as a bit of a shock
when Apollo samples showed that the Moon was very thoroughly baked early
in its history, which means no fossil ice and no water of hydration.
Any volatiles on the Moon are more recent arrivals.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry