POLARIMETRIC PROPERTIES OF THE LUNAR SURFACE AND ITS INTERPRETATION. PART II. TERRESTRIAL SAMPLES.
Final scientific rept.,
OBSERVATOIRE DE PARIS (FRANCE)
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For the interpretation of lunar polarisation measurements, samples were measured in the laboratory, using orange light of a wavelength of 6000 A. In all 61 samples were used, representing a wide variety of meteorites, volcanic ashes, basalts and other rocks. 31 samples have been seived into 4 grain size groups, with average grain sizes ranging from 160 micrometers down to 26 micrometers. Both the maximum degree of polarisation and the normal albedo are dependent of the grain size. The lunar data indicate a linear correlation between the log of the normal albedo and the log of the maximum degree of polarisation. The meteorites and the terrestrial samples are different, except for the two measured bronzide-chondrites and the fine-grained basalts. It is shown that several physical processes i.e. upwelling, proton darkening, diminution of grainsize and surface compaction have a bearing upon the normal albedo and the degree of polarisation. Author