A newly-identified spectral reflectance signature near the lunar South pole and the South Pole-Aitken Basin

摘要

Signal analysis of Galileo images of the Moon suggests the presence of an absorption band centered near 0.7 μm in the reflectance spectra of areas located adjacent to the equatorward walls of lunar craters at latitudes ranging from -58 to -78° and areas contained in the South Pole-Aitken Basin. We propose three potential explanations: an Fe²⁺→Fe³⁺ charge transfer transition in oxidized iron in clinopyroxenes (high-Ca bearing pyroxenes) or phyllosilicates (Fe- and Mg-bearing sheet silicates containing adsorbed H₂O and interlayer OH^-), or an effect of titanium in ilmenite (a common lunar opaque material). No identification of the mineralogy is conclusive. The presence and nature of the absorption feature could be confirmed using AMICA images of the lunar far side from the Japanese mission Hayabusa, spectroscopic results from the Japanese mission Selene scheduled for launch in 2007, or the Moon Mineralology Mapper on the Indian mission Chandrayaan-1