Theoretical origin of life: simple organic molecules in rock (Introduction)

by David Turell , Wednesday, March 31, 2021, 21:13 (1333 days ago) @ David Turell

A new discovery that ancient rocks hold simple carbon compounds and gasses:

https://www.nature.com/articles/s41467-021-21323-z#Sec9

"It is widely hypothesised that primeval life utilised small organic molecules as sources of carbon and energy. However, the presence of such primordial ingredients in early Earth habitats has not yet been demonstrated. Here we report the existence of indigenous organic molecules and gases in primary fluid inclusions in c. 3.5-billion-year-old barites (Dresser Formation, Pilbara Craton, Western Australia). The compounds identified (e.g., H2S, COS, CS2, CH4, acetic acid, organic (poly-)sulfanes, thiols) may have formed important substrates for purported ancestral sulfur and methanogenic metabolisms. They also include stable building blocks of methyl thioacetate (methanethiol, acetic acid) – a putative key agent in primordial energy metabolism and thus the emergence of life. Delivered by hydrothermal fluids, some of these compounds may have fuelled microbial communities associated with the barite deposits. Our findings demonstrate that early Archaean hydrothermal fluids contained essential primordial ingredients that provided fertile substrates for earliest life on our planet.

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"As yet, however, such distinctive organic molecules have not been found in rocks that directly testify to the emergence of life on our planet. (my bold)
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"Here we report on the presence of biologically-relevant primordial organic molecules in primary fluid inclusions trapped in barites of the c. 3.5 billion-year-old Dresser Formation. To explore the full range of volatiles, we combined gas chromatography–mass spectrometry (GC–MS), microthermometry, fluid inclusion petrography, and stable isotope analysis. Our findings reveal an intriguing diversity of organic molecules with known or inferred metabolic relevance and provide a strong clue as to how ancient hydrothermal fluids sustained microbial life ~3.5 billion years ago.

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"Black barites studied here classify as primary hydrothermal sediments that precipitated from discharging fluids. This interpretation is additionally supported by the facts that (i) the originally sulfidic stromatolite interbeds are still largely intact and show no indications for a progressive replacement by barite and (ii) that the barite does not contain relicts of potential precursor materials. Our observations are therefore consistent with earlier studies that argued for a primary, synsedimentary origin of the Dresser barites analysed herein (i.e. precipitation in surface environments linked to hydrothermal activity)"

Comment: Simple carbon-based molecules do not make the complex molecules such as amino acids necessary for living organisms, but it shows possible molecular substrates to help start life.