Figuring out how life first took off is (much like) rocket science!

摘要

A pedagogical comparison of emergence-of-life research and rocket science is made in order to inform how environmental disequilibria at the ocean/crust interface on the early Earth - a 1 V battery - forced life's emergence as an inescapable mechanism for their dissipation. Likely fuels and oxidants to drive life into being were hydrogen plus methane, borne by rising alkaline hydrothermal solutions, juxtaposed with ocean waters containing dilute nitric plus carbonic acids carbureted along the outside of a spontaneously precipitated semipermeable metal hydroxide/sulfide mound. As a comparison, hydrogen and methane can also be used as fuels for rockets, with nitric acid as an oxidant, carefully distributed through the mixing head to the combustion chamber. Whereas a full burn is the goal of the rocket engineer, the first living entities were best served by incomplete reactions and thereby the production of metastable intermediates that could further interact to beat the first metabolic pathway to life. In this analogy the hydrothermal mound is broadly comparable to the rocket while individual engines comprise the variable valence and conformationally flexible mineral, green rust (similar to[Fe42+Fe23+(OH12](2+)[CO3 center dot 3H(2)O](2-)) dosed with Ni, Co, Mo and W. With its internal layers of water and counter ions, we also compare the operations of green rust to a slow ramjet. This green rust 'ramjet' is driven by steep gradients in protons, electrons, anions and uncharged molecules, through the hydrous interlayers from either side of the mineral membrane separating the contrasting fluids and which green rust partly comprises. The mineral can rapidly reduce nitrate to ammonia and, therefrom, aminate pyruvate to the amino acid alanine. The higher amino acids may also be synthesized and polymers thereby act as primitive proteins, enzymes and cell walls. The main challenge now is to figure out how this green rust system, with its variable valence pattern of 2 + and 3 + cations, could govern growth and reproduction and, eventually, evolve toward a replicative world partly governed by nucleotides. Inanimate rockets of course, need their guidance systems installed, and most are fully autonomous.