On Sat, 13 Jan 2024 08:49:08 -0800
erik simpson <eastside.erik@gmail.com> wrote:

https://www.nature.com/articles/s43247-023-01196-4.pdf

Generation of long-chain fatty acids by hydrogen-
driven bicarbonate reduction in ancient alkaline
hydrothermal vents

[Cut'n'Pasted]

AHV conditions at <100 °C.
We hypothesised that having both continuous flow and pressurised
hydrogen would enable the generation of long carbon
chain fatty acids on Fe-minerals. Therefore, we built a pressurised
continuous flow reactor to more accurately mimic key elements
of the chemistry of upwelling alkaline hydrothermal vent fluid
and Hadean-Archaean surface water mixing. An HCO3
− solution
was mixed with dissolved H2 at concentrations comparable to
modern and putative ancient AHV, kept in disequilibrium at
90 °C and 16 bar and passed over magnetite (Fe2O3), a mineral
associated with AHV54 (Detailed method in Supplementary
Methods). We used a range of complementary bulk and mineral
surface-sensitive techniques to analyse the organic molecules
generated in experiments, alongside monitoring changes in the
inorganic chemistry.
Results
Characterisation of organic material generated in the AHV
simulator. The magnetite and quartz composition before and
after the reactions were obtained with X-ray diffraction (Supplementary
Note 1 and Supplementary Data 1), which indicated
that these minerals were unaffected by the reactions in the AHV
simulator. Methane levels above background levels were not
observed in the AHV simulator gas trap (Supplementary Methods)
in the test experiment using magnetite following the HCO3
−
and H2 hydrothermal reaction or in the control experiments
where HCO3
− was absent, or where quartz replaced magnetite
(Supplementary Note 2). In contrast, low molecular weight
organic acids (C2–C4) were detected (µM concentrations) in the
aqueous phase of the test experiment, but not in control experiments (Supplementary Note 3 and Supplementary Data 2) and
the presence of such material in the effluent was indicated using
1H nuclear magnetic resonance (Supplementary Note 4).
Importantly, after 16 h, even under our low temperature hydrothermal
conditions (90 °C, 16 bar total pressure, 5.5 mM H2 and
110 mM HCO3
−, pH 8.5 to 9.3) our thermal desorption/volatilisation-gas chromatography-mass spectrometry (TD-GC/MS)
analyses demonstrated that a range of functionalised straight and
branched long-chain (C10-C20) aliphatic organic compounds were
generated on the magnetite after the reaction with H2 and
HCO3
− (Fig. 1a). This included methyl, hydroxyl, ketones, a
...


--
Bah, and indeed Humbug.

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