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January 23rd, 2015: Widespread mixing and burial of Earth’s Hadean crust by asteroid impacts

Posted on Aug 6, 2014 in Seminars

Simone Marchi (Univ. of Colorado at Boulder/Southwest Research Institute)

In this talk I will present a new bombardment model of the Hadean Earth that has been calibrated using existing lunar data and terrestrial highly siderophile elements. We find 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, we will discuss an intriguing orrelation between the age distribution of Hadean zircons and the impact flux, possibly indicating impacts played an important role in Hadean zircon formation. Finally, by tracking the magnitude and timing of early collisions, we find that existing oceans would have repeatedly boiled away into steam atmospheres as a result of large collisions as late as about 4 billion years ago.