Newsgroups: sci.space
Path: cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!noc.near.net!howland.reston.ans.net!gatech!udel!rochester!dietz
From: dietz@cs.rochester.edu (Paul Dietz)
Subject: Re: Life on Mars.
Message-ID: <1993May15.111337.29526@cs.rochester.edu>
Organization: University of Rochester
References: <1stqef$903@access.digex.net> <1993May13.165407.1225@cs.rochester.edu> <lv8fpoINNqo1@exodus.Eng.Sun.COM>
Date: Sat, 15 May 1993 11:13:37 GMT
Lines: 27

In article <lv8fpoINNqo1@exodus.Eng.Sun.COM> jmck@norge.Eng.Sun.COM (John McKernan) writes:

> Some new information has been discovered recently. Microscopic fossils
> have been found in VERY old rocks. The theory is that this life is so
> old that it must have been destroyed during the periodic intense 
> meteorite bombardments that were a feature of the early solar system.
> Under this theory life originated on Earth multiple times (between
> multiple meteorite bombardments), and therefore the conditions for
> the creation of life cannot be that unlikely.


This was all badly reported in the news.  There is no evidence that
signs of life found in old rock predate putative planet-sterilizing
events.  Rather, the argument was that if life arose shortly the last
sterilizing event, then it must be easily formed.  The *inference*
was that life originated before and was destroyed, but there was
no evidence of that.

However, even this argument is flawed.  It could well be that origin of
life requires specific conditions (say, a certain composition of the
atmosphere) that do not last for long.  So, perhaps life formed
early only because it would have had no other chance to do so,
not because it was likely that life would originate under those
conditions.

	Paul F. Dietz
	dietz@cs.rochester.edu
