Dependence of the Hydration of the Lunar Surface on the Concentrations of TiO₂, Plagioclase, and Spinel

Abstract

We investigate the interrelation between the hydration of the lunar regolith and the mineral composition of the surface of the Moon with respect to the concentrations of plagioclase, TiO2 (highly correlated with the oxide mineral ilmenite), and Mg-spinel. The spectral properties of lunar regions with a low concentration of plagioclase or a high concentration of TiO2 or Mg-spinel show a significant reduction in hydration at lunar midday compared to other compositions. This suggests that these oxide minerals contain less of the strongly bound OH component, which is not removed at lunar midday. The time-of-day-dependent variation of the 3 μm band depth is greater in TiO2-rich areas compared to other mare regions. The TiO2-rich regions therefore appear to have a strong tendency to adsorb solar wind-induced hydrogen into binding states of low energy that can more readily desorb and readsorb OH/H2O on a daily basis.

Keywords

• moon
• composition
• hydroxyl
• ilmenite
• plagioclase
• Mg-spinel