Structure of the South Pole-Aitken lunar basin

Abstract

The hypsometric map and the basin height profiles, for the first time relying upon a spherical daturence surface, have been constructed based on the generalization of the heights measured within the hemisphere including the ring structure of the South Pole-Aitken basin. The distribution of the major chemical elements (Fe and Th), depending upon the structure height levels, has been obtained. The relationship between these lunar rock indicators and the height levels of the rock preferential distribution has been revealed. The outer basin ring has been distinguished and the ring structure of the central basin depression has been revealed against a combined hypsometric and geochemical background. A total basin diameter of about 3500 km has been reliably determined for the first time. A unique feature of the basin structure consists in that the arrangement of the basin inner rings does not show a central circular symmetry, which can indicate that a hypothetical impactor moved along the trajectory (or orbit) oriented almost normally to the ecliptic plane. In combination with the revealed very small depth-diameter ratio in the initial basin structure, this circumstance makes it possible to put forward the hypothesis that a comet impact produced the South Pole-Aitken basin.