Prebiotic reactions in a Mars analog iron mineral system: Effects of nitrate, nitrite, and ammonia on amino acid formation. (1st November 2022)

• Record Type: Journal Article
• Authors: Barge, Laura M.; Flores, Erika; Weber, Jessica M.; Fraeman, Abigail A.; Yung, Yuk L.; VanderVelde, David; Martinez, Eduardo; Castonguay, Amalia; Billings, Keith; Baum, Marc M.
• Is Part Of: Geochimica et cosmochimica acta. Volume 336(2022)
• Page Start: 469
• Page End: 479
• Publication Date: 2022-11-01
• Subjects: Nitrate -- Iron hydroxides -- Astrobiology -- Prebiotic chemistry; Geochemistry -- Periodicals; Meteorites -- Periodicals; Géochimie -- Périodiques; Météorites -- Périodiques; Geochemie; Astrochemie; Electronic journals; 551.905
• DOI: 10.1016/j.gca.2022.08.038
• Languages: English
• ISSNs: 0016-7037

Abstract

Abstract: Iron minerals are highly reactive drivers of abiotic/prebiotic organic chemistry, and in the presence of ammonia (NH3 /NH4 + ) or other reduced nitrogen (N) compounds, have been shown to promote amino acid synthesis from organic precursors. On early Mars, oxidized nitrogen species (NOx − ) such as NO3 − and/or NO2 − may have been present, which could be reduced by Fe(II) to form various species including N2 O and/or NH3 /NH4 + . The production of NH3 /NH4 + from Fe(II)-driven NO3 − or NO2 − reduction may be able to feed into prebiotic organic reactions including amino acid formation. In this study, we tested whether iron mineral-driven reduction of NO3 − or NO2 − could provide a source of NH3 /NH4 + to form amino acids from two prebiotically relevant precursors (pyruvate and glyoxylate); or, whether an exogeneous source of NH3 /NH4 + would be required. We observed that pyruvate and glyoxylate reacted with Fe-oxyhydroxide minerals in NOx − -containing experiments to form reduced hydroxy acid products; and in experiments containing only NH3 /NH4 +, amino acids were also formed. However, significant amino acid formation was not observed in any experiments containing NO3 − or NO2 − unless sufficient NH4 + was also added; furthermore, colorimetric analysis did not show any generation of NH4 + from NO3 − /NO2 − reduction at these conditions. NO2 − was observed to be highly reactive with Fe 2+ and Fe(II)-bearing minerals, resulting in Fe oxidation during mineral precipitation and the formation of oxidized mineral phases (hematite). The Fe(II)/Fe(III) ratio in oxyhydroxide minerals is an important parameter for determining organic product distributions from pyruvate and glyoxylate; therefore, Fe-mediated NOx − reduction does impact organic chemistry. However, amino acid formation, at least under these conditions, would also require an exogenous source of NH3 /NH4 + or other reduced N species. These results have implications for organic-N chemistry on early Mars, as well as for some early Earth origin of life scenarios regarding organic synthesis in mineral-containing systems.