Possibility of H and S Detection on the Moon by Selene Mission

Introduction: The possible existence of water ice in permanently shadowed regions near the lunar poles has been postulated by Watson et al. [1]. The delivery rate of water into the cold lunar polar craters due to degassing from the lunar interiors, micrometeorite bombardment, solar wind, and comet impacts was investigated [2]. Some experiments have been made to search for the existence of water in the polar regions. Areas with ice-like radar echoes were detected during the Clementine-Deep Space Network bistatic experiment [3]. Another attempt to detect hydrogen-containing compounds near the lunar poles was made using Lunar Prospector neutron data [4]. The mass of water ice was estimated as 2*10 g in the south polar region, and its mass fra ction as about 1.5 % in the south polar caps [4]. The observable amount of lunar polar hydrogen can be explained by action of solar wind flux on the lunar surface [5]. However, a recent analysis of hydrogen content based on Lunar Prospector data supports the idea that a significant portion of the enhanced hydrogen near the poles is most likely in the form of water molecules [6]. The possibility of polar volatiles other than water ice has been considered by some investigators [7-9]. Sprague et al. [7] proposed that unusual radar properties of Hermean poles make a compelling case for the presence of elemental sulfur at the upper layers of polar regolith on Mercury. Comet hypothesis for the origin of lunar polar volatiles has not been well studied. The fraction of cometary matter captured by lunar gravitation field is estimated by Berezhnoi and Klumov [10], which showed that volatile compounds in lunar temporary atmosphere finally accumulated completely in cold traps. Comet impacts deliver H2O, CO2, SO2 ices to cold traps.