[extropy-chat] volcanic gas- origins of life?

[Hal Finney]

Amara Graps writes:
> Filling in some parts from what Jeff Davis pointed extropy-chat to:
>
> http://www.eurekalert.org/pub_releases/2004-10/sri-cov100704.php
> ...
> Looking up the paper, to see the abstract and some details:
>
> Science, Vol 306, Issue 5694, 283-286 , 8 October 2004
>
> Carbonyl Sulfide-Mediated Prebiotic Formation of Peptides
> Luke Leman,1 Leslie Orgel,2 M. Reza Ghadiri1*
>
> ... We show that carbonyl sulfide (COS), a simple
> volcanic gas, brings about the formation of peptides from amino acids
> under mild conditions in aqueous solution. Depending on the reaction
> conditions and additives used, exposure of -amino acids to COS
> generates peptides in yields of up to 80% in minutes to hours at room
> temperature.

It seems strange that only now would people be doing testing to see how
reactions would occur in the presence of what I gather is a relatively
common gas in the atmosphere of the early earth.  I watched the PBS
show Origins a few weeks ago, and they were still talking about the 1953
Urey-Miller experiment in which an atmosphere thought to mimic that of the
prebiotic Earth was exposed to a spark gap (meant to simulate lightning);
after a few days testing showed the presence of amino acids.

The problem is that the gases used in that experiment are no longer
thought to represent a good model of Earth's atmosphere.  That makes the
experiments somewhat meaningless as evidence of anything other than
that amino acids can form in some hypothetical conditions that as far
as we know never occured anywhere but in that experiment.  Yet people
still point to this experiment as evidence of how life originated.

Why don't we hear about people running revised versions of that experiment
with a more accurate mixture of gases, including the one used in this
experiment, carbonyl sulfide?  Is it that there is still too much
uncertainty about what was present and their relative concentrations?
Or is it that the revised versions don't work, they don't get the nice
pat results of Urey/Miller with amino acids all laid out for us?

One page I found that sheds some light on this is by Leslie E. Orgel,
http://www.geocities.com/CapeCanaveral/Lab/2948/orgel.html.  He describes
Miller's work and then discusses some followups:

"Since then, workers have subjected many different mixtures of simple
gases to various energy sources. The results of these experiments can be
summarized neatly. Under sufficiently reducing conditions, amino acids
form easily. Conversely, under oxidizing conditions, they do not arise
at all or do so only in small amounts."
...
"Doubt has arisen because recent investigations indicate the earth's
atmosphere was never as reducing as Urey and Miller presumed. I suspect
that many organic compounds generated in past studies would have been
produced even in an atmosphere containing less hydrogen, methane and
ammonia. Still, it seems prudent to consider other mechanisms for the
accumulation of the constituents of proteins and nucleic acids in the
prebiotic soup."

It seems strange that the question of the effects of today's best
models of the early atmosphere must be disclaimed with an "I suspect".
Apparently the work has not been done.

And now in this new research, someone throws in a new gas and gets a new
result, the formation of peptides (chains of amino acids).  I can't help
wondering, what might happen if you put in yet other gases that would
have been present?  And how meaningful is it to leave out gases that
might have significant effects?  I realize that it makes the experiment
easier to have just a few gases, but who knows whether some gas you
are leaving out of the experiment might totally change the results?

In general, the quality of work in this area seems to leave much to be
desired.  Granted, it is an extremely difficult and frustrating problem,
the origin of life, and perhaps not one that gets much funding.  But it
surely is of great philosophical interest.  And when you look at how
much money NASA is spending on Mars probes whose purpose is largely to
shed light on this area, it would seem easy to spare a few billion for
Earthly lab experiments, which is probably about a thousand times more
than is currently being spent.

Hal