Scientists examine role of iron sulfides in life's origins at early Earth hot springs

Scientists examine role of iron sulfides in life's origins at early Earth hot springs
by Simon Mansfield
Sydney, Australia (SPX) Dec 06, 2024

A recent study has revealed how iron sulfides may have influenced the emergence of life on early Earth by catalyzing the formation of prebiotic organic molecules in terrestrial hot springs. This research, conducted by an international team, suggests that these minerals played a pivotal role in converting gaseous carbon dioxide (CO2) into essential organic compounds through nonenzymatic chemical pathways.

Published in Nature Communications, the study explores Earth's ancient carbon cycles and the chemical reactions that may have sparked life, emphasizing the role of iron sulfides in the terrestrial hot springs origin of life hypothesis. Researchers from institutions such as the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences; Japan's National Institute for Materials Science; and the University of New South Wales, Australia, contributed to this work.

The abundance of iron sulfides in early Earth's hydrothermal systems has long intrigued scientists due to their capacity to drive key chemical reactions akin to modern metabolic processes. While much of the research on iron sulfides has focused on deep-sea hydrothermal vents, terrestrial hot springs have gained attention as alternative sites for life's emergence, thanks to their rich mineral diversity, chemical abundance, and sunlight exposure.

The research team synthesized nanoscale iron sulfides, including pure forms and those doped with elements commonly found in hot springs such as manganese, nickel, titanium, and cobalt. Experimental results demonstrated that these minerals could catalyze the H2-driven reduction of CO2 at moderate temperatures (80-120 C) and atmospheric pressure. Gas chromatography quantified methanol production during these reactions.

Manganese-doped iron sulfides exhibited the highest catalytic activity at 120 C, a process further enhanced by exposure to ultraviolet and visible light. The findings indicate that sunlight could have facilitated chemical transformations in early Earth environments. Additionally, the introduction of water vapor amplified the catalytic activity, supporting the hypothesis that vapor-rich hot springs were critical settings for prebiotic chemistry.

To unravel the mechanisms behind the reactions, researchers used diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for in-situ analysis. The data suggested a pathway involving the reverse water-gas shift (RWGS) reaction, where CO2 is first converted to carbon monoxide (CO) and subsequently hydrogenated to methanol. Density functional theory (DFT) calculations revealed that manganese doping significantly reduced activation energy and enhanced electron transfer, improving reaction efficiency.

The study likens the redox properties of iron sulfides to modern metabolic enzymes, presenting a plausible chemical framework for prebiotic carbon fixation. These findings open new avenues for understanding life's origins and inform ongoing efforts to search for extraterrestrial life.

Research Report:Iron sulfide-catalyzed gaseous CO2 reduction and prebiotic carbon fixation in terrestrial hot springs