Deciphering Earth's Earliest Atmospheres: A Micrometeorite-Based Multi-Proxy Reconstruction of Atmospheric Composition Across the Great Oxidation Event

Objective

The PRECAM-MM project aims to reconstruct Earth's ancient atmospheric composition, including triple oxygen isotopic composition, CO2 partial pressure, and Gross Primary Productivity (GPP), from the Mesoarchean to the Paleoproterozoic eras (~3.2 to 1.6 billion years ago), specifically targeting the Great Oxidation Event (GOE). This will be achieved through the novel analysis of fossil I-type cosmic spherules (melted micrometeorites) extracted from precisely dated geological formations like the Keonjhor Paleosol, Vempalle Dolomite, and Kajrahat Limestone in India. The methodology involves a comprehensive multi-proxy approach, beginning with the extraction and initial characterization of micrometeorites using techniques such as SEM, EPMA, µXRF, and µRaman to determine their cosmochemical nature and preservation state. Subsequently, detailed isotopic analysis will be performed, including oxygen isotopes via LG-SIMS (at CNRS-CRPG during a secondment) and LF-IRMS, and iron isotopes using LA-MC-ICP-MS. These micrometeorite-derived data will then be integrated with existing geochemical proxies from sedimentary rocks to develop a unified paleoatmospheric evolution model, providing a more robust understanding of the transition from an anoxic to an oxygenated atmosphere. Under the supervision of Prof. Steven Goderis at VUB and with a secondment to Prof. Yves Marrocchi at CNRS-CRPG, the project offers extensive training in advanced micro-analytical techniques, data integration, and grant writing, significantly enhancing the researcher's career prospects in cosmochemistry and early Earth studies. The expected impacts are substantial, contributing scientifically by providing direct insights into cosmic dust's role in atmospheric evolution, societally by informing long-term climate discussions and highlighting the extraterrestrial influence on Earth's habitability, and economically by demonstrating a cost-effective approach to planetary science.