Thursday, October 29, 2015 - 2:00pm
Dr. Sujoy Mukhopadhyay of UC Davis will give a talk at Speakers Club entitled "Probing terrestrial accretion and early environments using noble gases" on Thursday October 29 at 2:00 PM in Webb Hall 1100.
Earth’s violent accretion3He to primordial 22Ne in the mantle preserves a record of magma oceans on the early Earth. Importantly, the 3He/22Ne ratio of the Earth’s shallow depleted mantle is significantly higher than the deep mantle. To explain this observation, I propose at least two giant impact-induced atmospheric blow-off and partial mantle magma oceans. While the geochemical data require substantial atmospheric loss via giant impacts, little of the water ocean would have to be lost. The need for atmospheric loss inferred from the noble gas data could be reconciled with the dynamics of giant impacts by considering the new high-spin Moon formation hypothesis.
New Xe isotopic data indicate that the catastrophic mantle outgassing and atmospheric blow-off events inferred from 3He/22Ne ratios were accomplished between ~40 to 70 Myrs after the start of the Solar System. These Xe data also require that reservoirs formed early in Earth’s history (<100 Myrs) have survived intact in the deep mantle till present day and mantle convection has led to at most seven overturns of the mid ocean ridge basalt source over the past 4.5 billion years.
October 21, 2015 - 10:18pm