Abstract EANA2024-43

Understanding the origin of life crucially relies on identifying the source of the organic compounds involved. Meteorites contain a variety of such compounds, including amino acids, carboxylic acids, nucleobases, and monosaccharides. This discovery suggests that meteorites might have served as the carriers of these essential building blocks of life. Amino acids present in carbonaceous chondrites (CC) range from trace amounts to several hundred parts per million, containing both proteinogenic (essential for protein formation) and non-proteinogenic varieties. However, for these amino acids to participate in the prebiotic chemistry, they must first be liberated from their meteoritic hosts and introduced into the terrestrial environment. While our understanding of the early Earth's environmental conditions is limited, various theories suggest that hydrothermal systems could have provided suitable settings for the emergence of life. Around 4.4 billion years ago, during the Hadean era, the Earth likely featured widespread volcanic activity with hydrothermal fields and multiple hot spring systems on subaerial surfaces. This environment would have facilitated the accumulation and concentration of organic compounds from exogenous sources in small freshwater bodies on volcanic landmasses. Exposure of CC to water would have also triggered the alteration of their mineral components. To investigate this, we conducted experiments involving immersing meteoritic samples in solutions simulating terrestrial, prebiotic ponds of the early Earth. We then analysed the solutions and meteoritic residues at intervals of increasing duration.

Powdered fragments of the Tarda and Aguas Zarcas CC were subjected to aqueous solutions with varying pH ranges and temperatures for a duration of up to 6 months, simulating the surface ponds on the early Earth. Following exposure, the liquid phase was separated from the solid residue, and subsequently, the resulting leachates were analysed using UHPLC-OT-MS (Ultra-High Performance Liquid Chromatography-Orbitrap-Mass Spectrometry), targeting amino acids. The identification and quantification of amino acids were carried out utilizing an in-house standard containing the amino acids of interest. The dried residue samples were studied through XRD (X-ray Diffraction), with fixed sample illumination ranging from 5° to 65° 2θ, employing a step increment of 0.02° and a counting time of 0.85 seconds per step. For the identification of minerals, we consulted the Crystallography Open Database.

A diverse array of intact amino acids was obtained from leachates of the Tarda and Aguas Zarcas meteorites, where both proteinogenic and nonproteinogenic amino acids were detected. Amino acids also displayed varying leaching capacities depending on the experimental condition to which they were subjected, as well as the class of the meteorite. XRD analyses of the CC residues indicated a generally consistent mineral composition before and after exposure to simulated pond conditions, except for the emergence of gypsum patterns in treated samples compared to pristine ones. The findings depicted here indicate that amino acids can be released into hydrothermal solutions originating from their meteoritic sources. While our understanding of the full role of prebiotic ponds remains incomplete, this study underscores their significance as potential cradles for life's emergence, where meteoritic amino acids may have been readily accessible for prebiotic chemistry.