Widespread Mixing and Burial of Earth’s Hadean Crust by Asteroid Impacts
When: December 7, 2016 2PM PST
In this talk, Marchi will present a new bombardment model of the Hadean Earth that has been calibrated using existing lunar data and terrestrial highly siderophile elements. He has found that the surface of the Hadean Earth was widely reprocessed by impacts through mixing and burial by impact-generated melt. This model may explain the absence of early terrestrial rocks. Furthermore, he will discuss an intriguing correlation between the age distribution of Hadean zircons and the impact flux, possibly indicating impacts played an important role in Hadean zircon formation. In addition, by tracking the magnitude and timing of early collisions, he concludes that existing oceans would have repeatedly boiled away into steam atmospheres as a result of large collisions as late as about four billion years ago. Finally, he will discuss recent developments in understanding impact-induced effects on the tectonic evolution of the early Earth with implications on the faint young Sun paradox.