How Much Melt Breccia Can Be Found in South Pole-aitken Basin?

Introduction: The South Pole-Aitken (SPA) Basin is the largest, oldest basin on the Moon. The extreme size of the basin, ≤2,500 km in diameter and a present depth of up to 13km [1,2], suggests that much of the upper crust would have been excavated during the formation/impact event, exposing the lower crust or upper mantle. Also, a large volume of impact melt breccia containing extensive lower crust components is also expected to have been created [3, 4]. Samples of the SPA melt breccia can be used to constrain the age of the basin as well as the composition of the lower crust. However, some of the unique features of the SPA basin have been affected by billions of years of subsequent evolution of the lunar surface. While several processes have been active during this time (extensive impact cratering, emplacement of mare basalts, lateral mixing by craters, space weathering, etc.), this abstract will only consider the early emplacement and mixing of basin ejecta within the interior of SPA. Previous work [5] estimated the amount of foreign material that has been introduced into the center of SPA by later basin forming events. We extend these studies to include the interaction and mixing of this ejecta with the surface of the basin. Investigation of these processes allow an estimation of the percent of current surface components that is derived from the original SPA melt breccia. Approach: The basins used in this study include all identified basins on the same lunar hemisphere of SPA [6]. These basins are shown in Figure 1 and listed in Table 1. The Imbrium basin is also included because it is one of the most recent and largest basins on the Moon.