High Quality Content by WIKIPEDIA articles! The Moon has been shown to have a "tail" of sodium ions too faint to be detected by the human eye. It is hundreds of thousands of miles long, and was discovered in 1998 as a result of Boston University scientists observing the Leonid meteor storm. The Moon is constantly releasing atomic sodium gas from its surface, and solar radiation pressure accelerates the sodium atoms in the anti-sunward direction, forming an elongated tail which points away from the Sun. The 1998 Leonid meteor shower temporarily tripled the mass of the tail by adding to population of sodium atoms being outgassed by the Moon.