Depletion of Moderately Volatile Elements by Wind-Driven Mass-Loss in the Early Solar Nebula

The pervasive depletion in meteorite parent bodies and terrestrial planets of Moderately Volatile Elements (MVE), having condensation temperatures between ~ 650–1350 K, is a long-standing, unsolved puzzle. Processes such as incomplete condensation of the nebular gas, mixing of volatile-rich and volatile-poor meteoritic components, an MVE-depleted parent molecular cloud, or a natural outcome of the mixing of solids during the evolution of the solar nebula have been studied in the past. However, these efforts are yet to reproduce the trend with a wide range of physically self-consistent parameters. In this talk, we test a new hypothesis that Disk Winds, significant in both outer and inner part of the solar nebula, irreversibly remove the vapor phase materials, including the MVEs inside their evaporation fronts in the inner nebula, leaving nearly all forms of more refractory solids behind in larger particles. The inventory in the inner nebula is further replenished by the inward drift of unfractionated solid material from the cooler outer nebula. First, we discuss our 1+1D nebula evolution model for particles and gas with the recent implementations of disk winds, MVEs, and a new thermal opacity prescription consistent with higher temeperatures. The selected MVE species are tracked in both solid and vapor form in the course of our simulations. Next, we discuss how the depletion trend is dependent on the wind mass loss rate, underlying level of global turbulence, and duration of the process. We can best reproduce the depletion trend using a higher mass loss than typically assumed in existing disk wind models, and a relatively short duration. We note that the conditions are reminiscent of so-called FU-or or YSO active stages. We also discuss the effects of porosities of the dust grains and the level of global disk turbulence on the said depletion trends. Finally, we discuss future work.