Heat flows through thin rock cracks can enhance the reactivity and concentration of prebiotic building blocks. This study demonstrates that geological networks of interconnected cracks can selectively purify a wide range of prebiotically relevant compounds, increasing their concentration ratios by up to three orders of magnitude. Using thermophoretic properties, the researchers numerically model and experimentally verify the effect of heat flows in rock fractures, showing that these flows can separate and enrich compounds like amino acids, nucleobases, and nucleotides. The study highlights how geologically driven non-equilibria could have facilitated prebiotic chemistry by creating parallelized reaction conditions. The results show that heat flows can significantly enhance reaction yields, as demonstrated by the dimerization of glycine, where selective purification of trimetaphosphate increased yields by five orders of magnitude. The findings suggest that heat flows in geological systems could have provided a natural mechanism for the separation and enrichment of prebiotic compounds, enabling the formation of biopolymers. The study also shows that this mechanism is robust across various conditions, including different crack sizes, pH values, solvents, and temperatures. The results have implications for understanding the origins of life on Earth, as they demonstrate how geological processes could have contributed to the development of prebiotic chemistry.Heat flows through thin rock cracks can enhance the reactivity and concentration of prebiotic building blocks. This study demonstrates that geological networks of interconnected cracks can selectively purify a wide range of prebiotically relevant compounds, increasing their concentration ratios by up to three orders of magnitude. Using thermophoretic properties, the researchers numerically model and experimentally verify the effect of heat flows in rock fractures, showing that these flows can separate and enrich compounds like amino acids, nucleobases, and nucleotides. The study highlights how geologically driven non-equilibria could have facilitated prebiotic chemistry by creating parallelized reaction conditions. The results show that heat flows can significantly enhance reaction yields, as demonstrated by the dimerization of glycine, where selective purification of trimetaphosphate increased yields by five orders of magnitude. The findings suggest that heat flows in geological systems could have provided a natural mechanism for the separation and enrichment of prebiotic compounds, enabling the formation of biopolymers. The study also shows that this mechanism is robust across various conditions, including different crack sizes, pH values, solvents, and temperatures. The results have implications for understanding the origins of life on Earth, as they demonstrate how geological processes could have contributed to the development of prebiotic chemistry.