Porous mineral formations near subsea alkaline hydrothermal vents embed microenvironments that make them potential hot spots for prebiotic biochemistry. But, synthesis of long-chain macromolecules needed to support higher-order functions in living systems (e.g., polypeptides, proteins, and nucleic acids) cannot occur without enrichment of chemical precursors before initiating polymerization, and identifying a suitable mechanism has become a key unanswered question in the origin of life. Here, we apply simulations and in situ experiments to show how 3D chaotic thermal convection-flows that naturally permeate hydrothermal pore networks-supplies a robust mechanism for focused accumulation at discrete targeted surface sites. This interfacial enrichment is synchronized with bulk homogenization of chemical species, yielding two distinct processes that are seemingly opposed yet synergistically combine to accelerate surface reaction kinetics by several orders of magnitude. Our results suggest that chaotic thermal convection may play a previously unappreciated role in mediating surface-catalyzed synthesis in the prebiotic milieu.thermal convection | prebiotic biochemistry | hydrothermal vents | chaos S ubsea hydrothermal microenvironments uniquely embed catalytically active mineral surfaces in the presence of thermal and chemical gradients, establishing disequilibrium pathways essential for emergence of biochemical complexity (1-3). Synthesis of organic monomers, for example, can be supported in these systems via pH conditions that favor hydrogen-dependent redox processes similar to the CO 2 reducing acetyl-CoA biochemical pathway (4). The recent discovery of alkaline vent systems [e.g., Lost City vent, mid-Atlantic ridge (5, 6)] has generated particular excitement because geochemical serpentinization yields surroundings abundant in hydrogen at moderate temperatures (150-200°C) (Fig. 1A). These attributes, combined with the excess hydrogen's ability to exothermically reduce carbon dioxide into methane, have fueled interest in elucidating the role of alkaline vents in orchestrating synthesis of prebiotic chemical precursors critical to the origin of life (4, 7).But, a favorable chemical environment alone is not sufficient to drive macromolecular synthesis owing to the extremely dilute concentrations of precursor compounds in the prebiotic ocean (8-11). Recent studies have explored the combined action of laminar (2D) thermal convection and thermophoresis as a physical enrichment mechanism, albeit in hairline-sized fissures (diameter d ≤ 100 μm) under steep thermal gradients (100-1,000°C/mm) (12-15). In contrast, surprisingly complex 3D flows characterized by chaotic thermal convection (16, 17) emerge over a broader pore size range [millimeters to centimeters, consistent with porosities in young active carbonate chimneys (18)] and under moderate temperature gradients (0.1-10°C/mm) (19,20) (Fig. 1A and SI Appendix). Here we apply simulations and in situ experiments to show how chaotic thermal convection under conditions mimi...