Material Mixing in the Earth-Moon Formation Scenario

Many of the seemingly contradictory results of prior Moon-formation simulations can be tied to numerical deficiencies of the standard SPH method. Oftentimes, insufficient mixing is the result of SPH's E0-error, and Lunar formation disks that seem to abruptly collapse are often plagued by overly diffusive artificial viscosity. While these numerical deficiencies are serious enough to drastically alter the evolution of any simulation, leading to unphysical results, they are nevertheless surmountable problems that can be eliminated through careful examination of each physical process in isolation, illuminating those processes where the assumptions that underlie the standard SPH method do not hold. When these numerical deficiencies are overcome, we may establish a common methodological framework for studying the Moon's formation, and that framework must necessarily include some form of a higher-order kernel and a linearly-limited artificial viscosity. My work is aimed at suggesting solutions to many of these problems, and at starting a conversation with the broader community about what that common methodological framework should include.