Colour and Spectral Characteristics of the Lunar Surface

Abstract

In the broad complex of optical studies of the Moon, the most complete information which does not lead to differences of opinion is available only for the photometric characteristics of its surface. The colour and polarization characteristics of the Moon's surface have been studied in less detail; and as far as the question of the colour contrasts on the Moon's surface is concerned, no unanimity of opinion has existed until recently, since colorimetric observations conducted by various investigators have often produced contradictory results. At the same time, the question of the existence and magnitude of colour differences on the surface of the Moon is not an academic one. The colour of the lunar surface reveals just such characteristics of its physical state as do other optical characteristics—such as photometric and polarizing peculiarities which inform us about the microstructure of the surface layer of the Moon. The observed colour of the lunar formations characterizes also the external layer, which represents the result of protracted and continuous influences on the lunar surface of various external factors—such as meteorites, micrometeorites, cosmic rays, and ultraviolet, corpuscular and X-ray radiation of the Sun, etc. Differences in colour of lunar features, just as differences in the albedo, depend on the characteristics of the basic lunar rocks and not on the changes which these rocks have undergone in the course of time. Therefore, although the alteration of characteristics of the external layer of these rocks does not permit comparison of the external optical characteristics of the Moon's topography with terrestrial rocks with certainty, one can, by means of various photometric and colour data, draw a number of conclusions about the characteristics of emerging basic rocks found on its surface.