True, they are based on assumptions of the composition of such a soup. But
a primordial soup in one form or another must have existed. Whether it be
the
composition as used by Miller/Urey or water or ....
If you are wondering if any soup existed then I am confused since we know
that there was an earth 4.5 billion years or so ago which must have had
some primordial composition.
> Such compounds, let alone nucleotides
< or polymers thereof, are extremely readily absorbed on a
< variety of rock and clay particles. In a primeval ocean
< therefore we would expect these concentrated organic soups
< to deposit their organic matter in the form of massive
< sediments over millions of years. These sediments would
Assuming that rocks this old can be found and that these rocks are in
'good' condition. At this moment the oldest rock (3.8 billion years ago)
are in no shape to help us out here.
Furthermore it assumes that the primordial soup was everywhere or at least
in the areas of interest and that the chemical composition of the
sediments would
1) reflect the soup 2) would not be changed over time.
< Proposed atmospheres and the reasons given to favor them are not
< discussed here. As described below, the more reducing atmospheres
< favor the synthesis of organic compounds in terms of both yields
< the variety of compounds obtained. Some of the organic chemistry
< can give explicit predictions about atmospheric constituents. Such
< considerations cannot prove that the earth had a certain primitive
< atmosphere, but the prebiotic synthesis constraints should be a
< major consideration.
< -- Stanley Miller, "Which Organic Compounds Could Have Occurred
< on the Prebiotic Earth?", Cold Spring Harbor Symposia on
< Quantitative Biology, Volume LII, pp 17-27.
----------------------------------------------------------
"The fact that certain prebiotic syntheses require a certain type
of atmosphere provides no evidence whatsoever regarding what the
primitive atmosphere actually was like. Instead, independent
evidence strongly suggests that the required atmosphere was not
present. Thus Miller's constraints on prebiotic synthesis are not
met, thus ..."
The question is 1) what is the relevance of tis 'independent and strong
evidence' ? The greenland rock reportedly are in bad shape to perform
chemical analysis 2) would the primordial soup and more importantly the
aminoacids be evident in the sediment ? 3) would the primordial soup in
the sediment be local or world wide ?
I do not know enough about sedimentation and marine chemistry to address
if the presence of aminoacids in the 'soup' should be reflected in the
sediments of those days.
It is hard to determine the depth dependent composition of the primordial
soup since we do not know what the earth looked like that long ago. But
according to the Urey/Miller experiment as well as other considerations
one would expect the production of aminoacids to be limited to the surface
area where 'evaporated' mixtures would precipitate similar to the
experiment. Would we therefor expect a homogeneously mixed 'ocean' ? Or
would there be variations in depth. Perhaps a "primordial oil slick"
So on one hand we have the lack of nitrates in sediments and on the other
hand an experiment which finds similar proportions of aminoacids as found
on meteorite rock. Does this mean that 1) meteorites were the source of
aminoacids on this earth ? 2) meteorites show that such aminoacids arise
in 'nature' and we should not be surprised to find them on the earth,
especially the primordial earth ?
I will have to do some research on Nitrate and sedimentation.
I was surprised when you stated that there was no primordial soup, which I
now understand as no primordial soup of the 'correct' consistence. I don't
believe that the Greenland rock is very useful for analysis. Although if
it were to believed it points to life already being present at that time.