ABSTRACT
Originally, it was of course assumed that the Moon must have an atmosphere dense enough to support life. This was the firm belief of observers such as Johann Schroter, the first really great lunar observer, wbo began his work in the late 1770s. William Herschel, discoverer of Uranus and arguably the most skilled of alJ observers, beUeved the habitability of the Moon to be "an absolute certainty'' (for good measure, he also beUeved in a cool,
P.\TRJCk MooRF
inhabited Sun), and in 1822 Franz von Paula Gruithuisen announced that he had identified a true dry with "dark gigantic ramparts", though, alas, there is nothing in this particular area other than low, haphazard ridges. This was in 1822; in the following decade many Americans were taken in by the celebrated Lunar Hoax, \vhen the New 'r'ork paper Sun announced that fantastic life-forms had been detected there by Sir John Herschel, who was busily surveying the southern skies from the Cape. (One earnest group even wrote to inguire whether there were any immediate plans to convert the Moon-men to Christianity.)
Low-type vegetation was still considered a possibility, even though a remote one, until less than a century ago, but so far as I know the last serious astronomer to believe in anything more advanced was WH. Pickering, who made very notable contributions to lunar and planetary astronomy. Pickering observed an occultation of Jupiter, in 1892, and recorded a dark band crossing the planer's disk, tilted with respect to the usual surface belts. This he attributed to the absorbing effect of a lunar atmosphere. He repeated the observation at several later occultations, and found that the dark band was seen only when Jupiter was cut the Moon's bright limb. At the dark or night side of the Moon it was never seen and Pickering concluded that the lunar atmosphere responsible for it was frozen solid during the Moon's night. He worked out that the ground density of the lunar atmosphere was about 1/1800 of the density of our own air at sea level.
