Abstract EANA2025-169

Understanding the origin of life is an enduring challenge for scientists. Most of the oldest traces of life are preserved in silica, which was abundant on the Archean earth, especially in hydrothermal environments where life most likely originated. Protomembranes are precursors of modern cell membranes which could have self-assembled in these hydrothermal environments from single-chain amphiphilic molecules produced by Fischer-Tropsh type synthesis, such as fatty acids and 1-alkanols. Recent studies have suggested that protomembranes, formed in a variety of conditions, resulted in structures that mimic the morphologies of ancient microfossils, which would obscure the interpretation of these specimens. To the best of our knowledge, there is currently no data on the impact of silica on the formation of protomembranes in plausible prebiotic conditions, or on their possible preservation through silicification. The ERC ProtoSigns project combines experimental, computational and analytical approaches to answer these questions.

In this study, we investigated 1) the formation and temporal stability of protomembranes exposed to silica and in conditions relevant to Archean hydrothermal systems, especially alkaline vents, and 2) the resultant structures and their implications for the interpretation of ancient microfossils. Protomembranes were formed with decanoic acid and 1-decanol, two molecules widely used in the study of protocells. We show that vesicles could self-assemble and remain stable in the presence of silica (1 mM to 0.5 M), and in pH (6 to 13) and temperature conditions (up to 70 °C) relevant to alkaline hydrothermal vents. Protomembranes were entombed with amorphous silica and subjected to high pressure and high temperature to simulate artificial fossilisation. The resultant structures will be characterised with advanced analytical techniques to generate a dataset of physical and chemical parameters and compared to microfossils with a biogenic origin.

Overall, this research aims to advance our knowledge of protomembrane evolution on the early Earth, link fossilised microstructures to the environmental context of their formation, and allow for a clearer interpretation of biosignatures from Earth and beyond.