The Interaction of Carbonaceous Chondrites with Prebiotic Environments: Implications for Amino Acid Leaching and Meteorite Alteration

Understanding the origin of life on Earth requires reconstructing how organic molecules first emerged and persisted within early planetary environments. Carbonaceous chondrites (CCs), primitive meteorites containing pre-solar materials and organic-rich matrices, play a central role in this reconstruction because they record both the chemical composition of the early Solar System and the alteration processes that occurred on their parent bodies. Besides being carriers of organic matter, CCs host dynamic mineralogical and geochemical systems capable of catalysing organic synthesis and mediating redox reactions. Their ability to preserve diverse amino acids, nucleobases, and macromolecular carbon over billions of years makes them valuable archives for understanding how extraterrestrial organics could have contributed to early Earth’s chemical evolution.

The early Earth, particularly during the Hadean eon, experienced heavy meteoritic bombardment that delivered substantial quantities of extraterrestrial material, including CCs enriched in amino acids and other prebiotic molecules. For these compounds to participate in biochemical pathways, they needed to be released from their mineral hosts into surface waters such as prebiotic ponds, hydrothermal settings, and evaporitic basins. Laboratory studies suggest that amino acids can be efficiently liberated through aqueous leaching, hydrothermal reactions, and hydrous pyrolysis, depending on environmental pH, temperature, and mineralogy. However, surface environments of the early Earth also received intense ultraviolet (UV) radiation in the absence of an ozone layer, and this radiation could both drive photochemical synthesis and degrade vulnerable molecules like glycine. The chemical composition of prebiotic ponds, whether ferrocyanide-rich, carbonate-dominated, or saline, would therefore have strongly influenced molecular stability, either enhancing organic complexity or accelerating degradation.

This thesis investigates how aqueous alteration shaped amino acid formation and preservation within CCs, how these molecules may have been released into Hadean surface environments, and whether they could have survived exposure to intense UV radiation on the young Earth. To address these interlinked processes, this thesis integrates meteoritic organic analysis, controlled leaching experiments, mineralogical characterization, and UV irradiation simulations. The results provide new insights into how organic matter in CCs was synthesized, preserved, released, and altered from parent-body environments to early Earth surface settings. They underscore that meteoritic organics were not uniformly stable or reactive but were instead shaped by a complex interplay of mineralogy, aqueous conditions, and environmental exposure. The work highlights carbonate-rich, salt-buffered pond setting as promising locations for persistent prebiotic molecule preservation.

Looking forward, the study emphasizes the need for expanded organic analyses across a wider diversity of meteoritic samples, more comprehensive modelling of early Earth aqueous systems, and broader experimental simulations of UV–mineral–organic interactions. With upcoming sample-return missions poised to deliver pristine materials from asteroids, comets, and icy moons, integrating high-resolution organic and mineralogical datasets will be crucial for tracing the early evolution of life’s chemical precursors across the Solar System.