A Surface Hydrothermal Source of Nitriles and Isonitriles
Paul B Rimmer1, Oliver Shorttle2,3
1Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, UK.
Life (Basel, Switzerland)
|April 27, 2024
Summary
Giant impacts on early Earth may have created graphite-rich crusts. This graphite could then produce essential prebiotic molecules like nitriles and isonitriles in hydrothermal vents, aiding the origin of life.
Area of Science:
- Astrobiology
- Geochemistry
- Planetary Science
Background:
- Giant impacts during Earth's Hadean eon could form hydrogen-rich atmospheres, leading to atmospheric carbon reduction.
- This reduced carbon, after atmospheric condensation and surface deposition, would be incorporated into the crust and converted to graphite upon heating.
Purpose of the Study:
- To investigate the consequences of graphite-saturated Hadean crust on prebiotic chemistry.
- To model the chemical products of volcanic gases interacting with graphite-rich crust in a surface hydrothermal vent scenario.
Main Methods:
- Modeling a surface hydrothermal vent system with nitrogen-rich volcanic gas passing through graphite-saturated crust.
- Simulating conditions at high temperatures (1500–1700 °C) and pressures (1–1000 bar).
Main Results:
- Equilibrium reactions with graphite purified the volcanic gas.
- Substantial quantities of prebiotic molecules were produced, including nitriles (hydrogen cyanide [HCN], cyanogen [HC3N]) and isonitriles (hydrogen isocyanide [HNC]).
- Predicted methyl isocyanide concentrations of approximately 1 part per million (ppm).
Conclusions:
- Graphite-saturated Hadean crust is a plausible source for prebiotic molecules in hydrothermal vents.
- Surface or shallow hydrothermal environments are identified as key geochemical sources for methyl isocyanide, crucial for the non-enzymatic activation of life's building blocks.
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