By Allan Mai ‘20

Experimental studies and thermodynamic calculations have shown that abiotic synthesis of amino acids and hydrocarbons – specifically during the hydrothermal alteration of mantle rocks – is theoretically possible. However, this phenomenon has only recently been demonstrated in a terrestrial setting. Benedicte Menez and his team at the Institut de Physique du Globe de Paris used high resolution imaging techniques to obtain evidence for the abiotic formation of aromatic amino acids under the Mid-Atlantic Ridge. Menez theorized that these aromatic amino acids could have formed from Friedel-Crafts reactions, a set of reactions that attach substituents onto an aromatic ring. Based on the researchers’ conclusions, it is very much possible that early organic compounds found their origins in the deep oceanic lithosphere using the iron rich saponite clay of the Earth’s mantle as a catalyst.

The abiotic synthesis of organic compounds is driven by the thermodynamically favored production of molecular hydrogen. H2 is formed when the reduction of water is coupled to the oxidation of ferrous iron in two types of rocks found in the deep ocean. Menez and his team focused their study on a serpentinized harzburgite – a rock consisting of orthopyroxene – that was recovered by deep sea drilling. Using scanning electron microscopy and other complex techniques, the researchers observed spectral features on this rock that indicated the presence of tryptophan, a type of amino acid. With the help of an advanced type of microscopy known as S-FTIR, these advanced imaging techniques also confirmed the presence of other nitrogen-bearing organic compounds.

These observations show that the clay-forming hydrothermal alteration of oceanic rocks has a crucial role in the synthesis of complex organic compounds such as tryptophan. Further studies in this field may reveal how ancient life forms utilized abiotic synthesis of amino acids to aid their own metabolic needs.

References

1. B. Menéz, et. al., Abiotic synthesis of amino acids in the recesses of the oceanic lithosphere. Nature (2018). doi: https://doi.org/10.1038/s41586-018-0684-z.  
2. Image retrieved from: https://unsplash.com/photos/0aNUp-RV-Pk