Possible physical processes causing transient lunar events |
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| Authors: | JE Geake AA Mills |
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| Institution: | 1. Department of Pure and Applied Physics, The University of Manchester Institute of Science and Technology (UMIST), Manchester Great Britain;2. Departments of Geology and Astronomy, University of Leicester, Leicester Great Britain |
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| Abstract: | Transient lunar events appear to involve two main effects: the obscuration of surface detail, and changes in brightness and/or colour which could be caused either by modification of the way in which incident sunlight is scattered, or by the emission of additional light. We find it difficult to explain the obscurations in any other way than to assume that clouds of fine surface dust are raised either by bursts of gas emission from surface fissures, or by impacts; the possible duration and density of such clouds are considered.Modification of the albedo of a dust surface by agitation has been demonstrated in laboratory experiments: under certain conditions the albedo may increase, but the change appears to be permanent at atmospheric pressure; it may be reversible under lunar vacuum conditions. The most likely lunar process of this type again seems to be the agitation of surface dust by gas emitted from fissures; also, the scattering of sunlight by dust clouds could, under some conditions, result in weak colour effects. Processes that could result in the emission of light include incandescence, luminescence or thermoluminescence, glow discharge in gas clouds (possibly enhanced by the presence of charged dust grains), and lightning-type discharge in dust clouds. We conclude that the lightning-type discharge is the process most likely to be bright enough to be visible from earth, against the sunlit moon.We therefore conclude that transient lunar events of the different types that have been reported could be explained by various processes that may occur in gas-borne dust clouds. |
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