Origin of volatile element depletion in the Earth

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Based on results of the proposals we propose in this renewal to expand the experimental studies to investigate evaporation and condensation behavior of volatile elements. In the former two periods of funding we concentrated on early nebular processes. We applied the experimental results to scenarios of chondrule formation and were able to explain - at least qualitatively - the different Mn/Na ratios of Earth, Moon, and Vesta. In the third period of funding we propose to quantify the evaporation and (re)condensation processes and fluxes that occurred within the first million years of the history of the solar system. We will also focus on the chemical fractionation between the Earth and Moon. The low contents of volatile elements (Na, K, etc.) in the Moon are the result of evaporation processes during the Moon-forming impact. These processes may have affected W, as WO3 is very volatile. The similarity in Hf/W ratios of Earth and Moon suggests that W was not volatized. This needs experimental verification. We therefore want to include WO3 in our experiments to find out how volatile WO3 really is. The results may have far reaching consequences for Hf/W dating. All experiments will cover a wide range of conditions (temperature, oxygen fugacity, total pressure (less than 1 bar), silicate melt compositions). In addition, we plan to extract relevant physical parameters based on a thermodynamic - kinetic analysis that allows further extrapolations. We will then be better able to model the processes that led to the depletion of volatile elements in the Moon (but also in Earth, other planets, and meteorites).