The first 500 million years of Earth history (4.5 to 4.0 billion years), known as the Hadean Eon, is the planet's 'dark age' as no rock older than 4 billion years are known in the geologic record. However, sand-grain sized crystals of the mineral zircon are found in younger quartzite rocks that are dated to almost as old as the Earth itself. Preliminary analyses suggest the possibility that the very early Earth shared more in common with present day than previously thought. This surprising result requires detailed examination, but Hadean grains are very rare, making up only about one part in a million of the sedimentary rock. Following an intensive analysis program, the lead scientist and his team have archived several hundred Hadean zircons and in this project, they plan to undertake experiments that may give us unprecedented insights into Earth's earliest evolution. The questions to address are the following: 1) Did early Earth differentiation include massive production of continental crust? 2) Did a mechanism akin to plate tectonics operate during the Hadean? 3) Why are rocks older than 4 billion years non-existent? 4) When did the atmosphere form? 5) Were there oceans during the Hadean Eon? 6) Are any of these ancient zircons of extra-terrestrial origin? To address these questions, the investigator will undertake nanoscale imaging of trace elements distributions in these zircons together with refined isotopic measurements.
This project showcases scientific and technical leadership in a field of global interest and aids in capturing the imagination of young people considering a career in science. Research outcomes are potentially of great public interest and could be akin to the results of a planetary exploration mission if the existing paradigm of Hadean Earth is overturned. Within the scientific community, evidence that the Earth was potentially habitable during the Hadean Eon would radically alter our views of the constraints on the emergence of life on this and other planets and lead genomic researchers to consider planting the roots of phylogenic trees a good deal deeper.
