Water on the moon: What is derived from the observations?

Abstract

Introduction: Further exploration and utilization of the Moon crucially depends on the answer to the question: is there water on the Moon and, if so, in which form? Being a differentiated silicate planet without an atmosphere and with high day temperature, the Moon did not inspire many expectations for presence of water or any other volatile with small molecular weight. A hope of finding ice on the lunar surface was resuscitated by the hypothesis of ice delivery to the lunar poles after cometary impacts (Watson et al. 1961, Arnold 1979). Water molecules from a comet nucleus were supposed to migrate in the lunar exosphere until being trapped in cold polar regions. Less important sources of migrating water could be water-bearing meteorites and volcanic gases. Much effort has been devoted to study formation of polar caps and ice stability (e.g. Butler 1997, Starukhina 2008).