The atmosphere of the Moon

The possible existence of a lunar atmosphere has both fascinated and challe nged astronomers for hundreds of years. Galileo searched for evidence of cl ouds, and Kepler imagined an Earth-like climate. Landings during the Apollo era brought instruments that measured a weak atmospheric pressure. Decades later, new spectrographic and imaging instruments detected sodium and pota ssium gas that extended to surprisingly large distances, making the Moon's gaseous environment appear as comet-like. The sources of the lunar atmosphe re involve the impact of sunlight, solar wind plasma and meteors upon the s urface to release atoms and perhaps molecules. Solar radiation and the grav itational influence of the Earth play dramatic roles in the subsequent evol ution of the lunar atmosphere.