🚀 go-pugleaf

In article <1992Oct30.023542.4610@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes:
|In article <1346@tdat.teradata.COM> swf@tdat.teradata.com (Stanley Friesen) writes:
|
|> This last is an extremely unlikely requirement.  The basic upshot of the
|> Urey experiment and its follow-ups is that organics form spontaneously
|> under most non-oxidizing 'medium-energy' conditions.  The presence of
|> organics in interstellar dust clouds just confirms this basic ubiquity.
|
|The Miller-Urey experiment is widely acknowledged to be irrelevant,
|as it assumed an atmosphere that likely bears little resemblance
|to the early earth.  Specifically, methane and ammonia are unlikely
|to have been abundant in the early atmosphere, as they are destroyed
|within centuries by UV light.

That is why I specified 'and follow-ups'.  Almost every variant atmosphere
that was either reducing or 'neutral' has yielded organics.  The results
do *not* depend particularly on the exact original chemistry - though the
exact set of organics produced does vary with the initial conditions.

|When performed with more reasonable gas mixtures, the experiments have
|much lower yields.  And, in any case, all that these experiments
|indicate is that some of the basic molecules of life are rather stable
|(and, importantly, that others are not), not that a particular source
|is where they first came from.

They show them to be formed under a wide variety of conditions, so they are
liekly to be present on most otherwise suitable planets - perhaps from
*multiple* sources.  In short, it is more *lack* of organics is more
extraordinary, and thus more unlikely, than thier presence.

|The unstated assumption here is that life would *not* have had a hard
|time originating back then.  We simply don't know enough about how
|life started to say this.

Not really, the all I was talking about here was the fact that our
oxidizing atmosphere destroys all unprotected organics.
|
|Au contraire!  Our ignorance about origin of life is profound, and
|very little progress has been made in dispelling it.  There is no
|really plausible model for the origin of life.  We're missing at least
|one, and possibly several, fundamental ideas.
|
Have you read Cairns-Smith's "Seven Clues to the Origin of Life"?
I consider that to be an extremely plausible model (though the best
reasons are not in that, now out-of-date, book).

Also, one could argue, based on the usual defnitions of life, that the
recently produced self-replicatinf RNA molecule *is* alive, and thus
we *have* made life in the laboratory. (Of course the exact definition
of life in the boundry cases is decidedly difficult, so one could also
make a case that it is not alive).
-- 
sarima@teradata.com			(formerly tdatirv!sarima)
  or
Stanley.Friesen@ElSegundoCA.ncr.com