Vapor drainage in the protolunar disk as the cause for the depletion in volatile elements of the Moon.

摘要: Lunar rocks are severely depleted in moderately volatile elements such as Rb, K, and Zn relative to Earth. Identifying the cause of this depletion is important for understanding how Earth-Moon system evolved aftermath Moon-forming giant impact. We measured Rb isotopic compositions lunar terrestrial understand why Moon. Combining our new measurements with previous data reveals that Moon has an 87Rb/85Rb ratio higher than Earth by +0.16 permil. This composition consistent evaporation into a vapor medium was ~99 percent saturated. Evaporation under saturation can also explain previously documented fractionations Ga, Cu show possible setting achieving same upon diverse volatilities through viscous drainage partially vaporized protolunar disk onto In framework alpha-disk model, alpha-viscosity needed ~99% calculated here 0.001 0.01, which where viscosity controlled magnetorotational instability.