Why Does Life Start, What Does It Do, Where Will It Be, and How Might We Find It
Life was driven into being on our planet to resolve the disequilibrium between the fuels [H2 > CH4] emanating from submarine alkaline hydrothermal springs with the oxidants [CO2 >> NO3-] dissolved in the acidulous Hadean Ocean. The two fluids were kept largely at bay by the precipitation of iron minerals at the spring. It was in the mineral barriers that this 'free energy' was first converted via a protometabolism to organic molecules. Thus, we can say that life - as an entropy generator - hydrogenated, and hydrogenates still, carbon dioxide to produce a small, but ever-renewed stock of organic molecules. Therefore, we may expect life to emerge on any wet and rocky world that has an ocean rich in carbon dioxide, augmented by a high potential oxidant such as nitrate/nitrite, sulfite and/or chlorate. One possible candidate is Europa [Astrobiology 2017, 17(12):1265]. Life reveals itself as whole cells or bioorganic molecules that themselves are far from thermodynamic equilibrium.
Technical Talk: How Green Rust Was Coopted as Embryonic Life's First Disequilibria-Converting Nanoengine
The absolute dependency of all forms of life on macro-molecular mechano-chemical engines to carry out all of their molecular transformations had to have been a 'fact of life' from its very beginning. In this context, we compare the functioning of a ram-jet to that of green rust microcrystals comprising a portion of a barrier separating the iron- and nitrate-rich acidulous Hadean Ocean from a serpentinization-driven hydrogen-bearing alkaline vent. We illustrate how nitrate and protons in the ocean could be rammed into the green rust interlayers and rapidly reduced to ammonia by electrons stemming from the hydrothermal fluids. Amination of carboxylates to amino acids follows [Astrobiology 2017, 17(10):1053], which in their turn polymerize to offer peptide nests to phosphate and FeS. Excess amyloidal peptides are extruded. The amyloid forms a matrix around the green rusts, and the subordinate layered mineral, mackinawite (FeS). Differentiation produces myriads of amyloid protocells, each with a contingent of iron oxyhydroxide/sulfide protoenzymes/nanoengines.