Amino acids are present in all known life, so identifying the environmental conditions under which they can be synthesized constrains where life on Earth might have formed and where life might be found on other planetary bodies. All known abiotic amino acid syntheses require ammonia, which is only produced in reducing and neutral atmospheres. Here, we demonstrate that the Fe-bearing hydroxide mineral ferroan brucite [Fe0.33,Mg0.67(OH)2] can mediate the reaction of nitrate and glyoxylate to form glycine, the simplest amino acid used in life. Up to 97% of this glycine was detected only after acid digestion of the mineral, demonstrating that it had been strongly partitioned to the mineral. The dicarboxylic amino acid 3-hydroxy aspartate was also detected, which suggests that reactants underwent a mechanism that simultaneously produced mono- and dicarboxylic amino acids. Nitrate can be produced in both neutral and oxidizing atmospheres, so reductive amination of nitrate and glyoxylate on a ferroan brucite surface expands origins of life scenarios. First, it expands the environmental conditions in which life's precursors could form to include oxidizing atmospheres. Second, it demonstrates the ability of ferroan brucite, an abundant, secondary mineral in serpentinizing systems where olivine is partly hydrated, to mediate reductive amination. Finally, the results demonstrate the need to consider mineral-bound products when analyzing samples for abiotic amino acid synthesis.
Keywords: astrobiology; origins of life; prebiotic chemistry.