Water on The Moon, I. Historical Overview

By mid-19th century, astronomers strongly suspected that the Moon was largely dry and airless, based on the absence of any observable weather. In 1892, William H. Pickering made a series of careful occultation measurements that allowed him to conclude that the lunar surface's atmospheric pressure was less than 1/4000th of Earth's. Any number of strange ideas arose to contradict this. Respectable scientists realized that significant amounts of water on the Moon's surface would rapidly sublime into the vacuum. Since 2007, however, the field has started another revolution in thought, and we describe this, including some lesser known aspects.