Materials and formation of the Imbrium basin

A study of Imbrium basin deposits has been conducted, including geologic mapping, analysis of orbital geochemical data, earth-based near-IR spectroscopy, and analytical modeling. The morphologic facies of the deposits display an unusual bilateral symmetry with respect to the main rim of the basin, which is thought to be 1160 km in diameter and composed of Apennine-Carpathian-Alpes mountain ranges. The Imbrium ring structure consists of six concentric rings ranging from 550-3200 km in diameter. The evolution of the target for the Imbrium basin impact is discussed. It is suggested that the Imbrium impact, which occurred 3.85 Gyrs ago, formed a basin predominantly by a proportional-growth crater-forming mechanism.