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From: ftdjt@acad3.fai.alaska.edu (THOMAS DAVID J)
Newsgroups: sci.space,sci.bio
Subject: Sagan on Mars
Keywords: mars,exobiology
Message-ID: <1990Jun25.232510.21951@hayes.fai.alaska.edu>
Date: 25 Jun 90 22:18:11 GMT
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 To anyone who may know:
I am trying to find a reference in which Carl Sagan described a hypothetical
Martian model in which he stated that Mars may go through long ice ages due to
precession.  During those ice ages, the Martian environment becomes more
favorable for life.  I believe the original article was published ca 1971.  I
found an indirect reference to it in Patrick Moore's GUIDE TO MARS (1977).  
However, Moore did not give a direct reference to a publication.  Any info
would be greatly appreciated.
Thanks,
Dave Thomas