On lateral mixing efficiency of lunar regolith

[1] To reexamine the potential for lateral mixing over large distances (>100 km) by impact craters, a mathematical model utilizing the stable probability distribution is proposed for estimating lateral mixing efficiency on the Moon. The proposed model divides material mixing into shallow slope and steep slope regimes. Mixing in the shallow slope regime conforms to the condition that the exponent of the power law describing lunar crater size frequency is larger than the exponent of the power law describing the rim thickness plus 2; otherwise the mixing is called the steep slope regime. The model suggests that in the shallow slope regime, lateral mixing on the Moon is efficient enough to deliver 20–30% exotic components over distances greater than 100 km (e.g., highland material to the mare). The model indicates that lateral mixing conforming to the steep slope regime is not efficient if linear addition of ejecta deposits is assumed because in this regime, impact cratering is driven by small craters reworking lunar surface, and the addition of crater ejecta is an invalid assumption. If the result of the proposed model for the shallow slope regime is applied to regolith layers below the reworked zone, a significant number of ‘‘exotic’’ components is predicted.