TITLE: Widespread Mixing and Burial of Earth’s Hadean Crust by Asteroid Impacts
PRESENTER: Simone Marchi
Southwest Research Institute, Boulder
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.
Simone Marchi’s research interests span from the formation and geology of terrestrial planets the moon and asteroids, to the spectroscopy and dynamics of minor bodies and meteorites. He is associated with several space missions, including: Dawn, Rosetta, BepiColombo and JUICE. He has been a fellow of the NASA Lunar Science Institute, the Observatoire de la Cote d’Azur, the German Aerospace Agency and Padua University. He holds a PhD in applied physics from the University of Pisa, Italy.