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BOUNCE starship-design: Non-member submission from ["Kevin 'Tex' Houston" <hous0042@email.umn.edu>]

>From stevev@darkwing.uoregon.edu  Mon Jul 21 20:18:34 1997
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Date: Mon, 21 Jul 1997 21:07:14 -0500
From: "Kevin 'Tex' Houston" <hous0042@email.umn.edu>
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Subject: Re: Aliens, why haven't they contact us?
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jimaclem@juno.com wrote:
> On Fri, 18 Jul 1997 00:42:30 -0400 (EDT) KellySt@aol.com writes:
> >
> >No way to know.  Can't even know anything basic about their celular
> >construction or chemistry.
> >
> Just a thought to consider folks.  All living organisms on this planet,
> including viruses have DNA and RNA constructed from the same four
> proteins, adenine, cytosine, guanine and tyrosine.  (And I do mean ALL
> life forms on this planet, from viruses to trees to us).  The chances
> that an alien microbe, or anything else, would use these same proteins
> seem rather small, thus rendering them and us relatively harmless to each
> other since we cant read each other's cellular codes.
> Jim

BZZZT!  Thank you for playing.  ;)  (sorry, I couldn't help it, I don't
often come across a subject that i know a whole lot about in this group,
but when I do, I pounce)

First, the observational evidence.  Large gas coulds in interstellar
space have been seen which contain each of these nucleotides in enough
abudance to outwiegh the earth.

Second the chemical evidence.  when simple molecules like ammonia,
methane, hydrogen cyanide etc are bombarded with UV, (in the lab here on
earth) They often breakdown into these very molecules

Third, the theoretical/thermodynamic reasons.  Left-handed amino acids
and right handed sugars are slightly, (theoretically) more
thermodynamically stable.  by being in a lower thermodynamic state,
these chiralities (fancy word for mirror image) tend to be favored in
chemical reactions.  Thus any organism that learned to eat
carbo-hyddrates would, through evolution, be drawn toward using
D-glucose (dextrose)  and would thus need proteins (if that's what they
used) with a left-handed structure

In short, any life that eats sugars and uses proteins, is VERY likely to
eat 'our' kind of sugar and use 'our' kind of protein.  

Chemical codes are a different matter, and would be a triple-edged
sword, while some alien microbe might be totally stymied by our
chemistry, Others would find it no problem, and some other kid of life
might be harmful to us as a side effect of thier own chemistry. 
Consider a life form that exhaled hydrogen cyanide for example:  While
they would be adapted to it, we would die in short order.  perhaps even
killing them with our exhaled carbon dioxide or water.

Kevin "Tex" Houston             http://umn.edu/~hous0042/index.html
Webmaster                       http://www.urly-bird.com/index.html
"Whoever undertakes to set himself up as a judge of Truth and
Knowledge is shipwrecked by the laughter of the gods." A. Einstein