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Re: Biological Origin of Earliest Fossils Substantiated



> The evidence of 3.85 billion year old life (if I remember correctly) comes
from Greenland and only consists of indirect isotope chemistry (no actual
fossils).

Those from Greenland are 3.8 Ga old. Those from Australia (not the Apex
Chert) are 3.85 Ga old. Both are isotope affairs.

>  C12: C13 ratios played a major role in this.  Because photosynthetic
organisms (bacteria and plants)

Many other lithotrophs, too (e. g. the symbionts of rift worms); not only
photosynthesizers take up carbon dioxide. The ratios are evidence for life,
but not for photosynthesis.

> In terms of Sulfur (like the S34 atom David mentioned), different analyses
using S32:S34 ratios can ascertain what type of life was present when a
certain sulfite

Sulfate.

> rock layer was deposited.  Chemoautotrophs (sulfate reducing bacteria)

That's not an equation. All sulfate breathers are chemotrophs, though.
Chemoautotrophs are all organisms that get their energy from chemicals
rather than light (chemo- rather than photo-) and build their biomass from
scratch (e. g. CO2) rather than from ready organic matter (-auto- rather
than -hetero-), IIRC. (I may have jumbled the latter with -litho-
vs. -organo-, which IIRC means that heterotrophs eat inorganic vs. organic
molecules... or something like that. :-) )

> make energy by adding hydrogen to sulfur atoms (usually cut from sulfate
dissolved in sea water).

Mmm... I'd rather express it that way: They breathe sulfate like others
breathe oxygen, nitrate... or (the methanogens) carbon dioxide. (To make it
more complicated, there are also heaps of prokaryotes that can breathe
thiosulfate, sulfite, and/or elementary sulfur in addition or instead.
Sulfur breathing -- attaching electrons and protons to it, which liberates
hydrogen sulfide -- is the last step of sulfate, thiosulfate, and sulfite
breathing.)

> This liberates the gas hydrogen sulfide, which, when given off by living
chemoautotrophs, is enriched in the lighter S32.  On the other hand,
nonbiologic sulfur evaporates, such as gypsum, contain a higher amount of
S34, the heavier isotope.

Correct AFAIK.

> Anyway, that's some basic geochemistry.

Microbiogeochemistry, to be exact (the word exists). :-)

> And, since the Mars concretions/contaminants/"fossils" were mentioned, I
have to say that I hope the new technology is used to study them.
Additional experiments cannot hurt.

Sure.