Contents — T through Z Locations and Compositions of Mare Ponds in South Pole - Aitken Basin on the Moon and Its

Locations and compositions of mare ponds in South pole-Aitken (SPA) basin are correlated to the structure of the SPA impact basin. The coverage of mare emplacements indicates that, inside the inner ring, the floor is relatively filled with mare deposits, whereas, in the regions of just inside the middle and outer rings, some mare extrusions exist. The lack of Hi-Ti basalt in mare ponds could result from the subsurface structure of the SPA post impact. Introduction: Most of volcanic activities were taken place in impact basins on the moon. The structure of impact basins is a key to the development of the magma chamber in the lunar mantle and the extrusion of the magma to the lunar surface. On the farside of the moon, the large impact basin –South pole-Aitken (SPA) exists, and mare ponds are well discrete to locate their eruptive sites relative to the impact basin. In order to examine the correlation of the impact tectonics of the SPA cratering and volcanic activities, locations and compositions of mare ponds are related to the SPA impact structure. Distribution of Mare ponds: Methods: The area coverage of mare ponds becomes an index of the eruptive activities. The coverage is estimated as a function of the radial distance from the center of the SPA crater (180°E, 50°S) using the estimate of locations and extended area of mare ponds [1]. The SPA is divided into several concentric circles with a radial distance of 4 degrees (approximately 120 km/bin). The total area of mare ponds in each bin is divided by the area of the bin, and then the coverage of the mare deposits is calculated. Results: Figure 1 shows the highest coverage in the SPA central region (<20degree ~ radial distance of 630 km) and small peaks near ring regions. A similar tendency is observed in the Orientale basin [2]. In the inner ring, crater floor is rather filled with volcanic emplacements, whereas, some mare extrusions were emplaced in regions just inside the middle and outer rings. This implicates that volcanic dikes from the lunar mantle could easily reach the surface inside and along rings. Tectonic normal faulting systems of middle and outer rings could assist the extrusion of magma to the surface. Inside the inner ring, the shallow-seated magma chambers could be erupted due to the lack of excavated crust excavated crust materials, brecciated deposits and lower-pressurized subsurface materials in the center of impact. Thus, the structure of the crater is possibly related to the inductions of volcanic emplacements. The depth of these faulting roots and magma source can be derived from the compositional analysis. Thus, in next, Clementine UVVIS data is utilized for further compositional analysis of mare deposits. Figure 1. Area ratio of mare ponds as a function of radial distance from the center of SPA crater (180°E, 50°S). The radius of the SPA crater is approximately 40 degree). Locations and estimated area of mare ponds [1] are utilized. The interior of the SPA is divided into several concentric circles with a radial distance of 4 degrees (~ 120 km/bin). The total area of mare ponds in a bin is divided by the area of the bin, and then the coverage of the mare deposits are calculated. FeO and TiO2 contents of mare ponds: Methods: In order to clarify the relationship between magma eruption and impact tectonics, the compositional variations of mare deposits are correlated to the impact structure of the SPA basin. Mare regions are selected from the original distribution of Clementine CD-ROM set. Photometric [3] and geometric corrections are applied. The method of Blewett et al. [4] estimating FeO and TiO2 contents for the hemispherical reflectance data is modified to estimate the contents for the images of bi-directional reflectance. Then, FeO and TiO2 maps of mare ponds are obtained. In order to avoid the effect of mixing of highland materials and debris from crater wall, the fresh and plain region with the area >10x10 pixels (2 x 2 km) are examined. Large Meteorite Impacts (2003) 4058.pdf