Spontaneous Mineral-driven electrochemical synthesis of organic matter under Martian conditions

Organic molecules preserved in Martian meteorites indicate that reduced carbon can form abiotically. Yet, the processes capable of generating and sustaining such material without biological or external energy inputs remain unresolved. Here, we demonstrate that a purely mineral-based system can spontaneously convert CO2 into complex organic matter through self-sustained electrochemical coupling. By embedding TiO2 and Fe3O4 nanoparticles within an amorphous SiO2 matrix, we construct a mineral assemblage that integrates an anodic phase, a cathodic phase and an electrolyte into a single electrochemical circuit. When immersed in CO2-bearing brine, this mineral junction drives directional electron transfer without applied voltage, illumination or heating. The system reduces CO2 to small oxygenated intermediates (e.g., formate, acetate) and subsequently converts them into aromatic-rich macromolecular carbon that accumulates at Fe-rich mineral interfaces. Nanoscale spectroscopic analyses show that these products closely resemble organic matter preserved in Martian meteorites. Unlike previous abiotic carbon synthesis studies that rely on isolated catalysts or external energy sources, this mineral assemblage sustains spontaneous, dark CO2 reduction driven solely by intrinsic mineral redox disequilibria. These findings identify mineral-driven geo-electrochemistry as a previously unrecognized pathway for abiotic carbon fixation and imply that similar processes could have operated on early Mars, early Earth and other water-bearing planetary bodies, while offering a conceptual framework for low-energy mineral-enabled carbon conversion.