Explanation of Transient Lunar Phenomena based on Lunar Samples Studies

Abstract

VARIOUS authors^1–4 have shown that transient lunar phenomena (TLPs) are unlikely to arise from the excitation of luminescence in lunar rocks by such agents as the solar wind⁵, but the luminescent efficiency is many orders of magnitude too low for this emission to be detected even by “line fill” techniques⁶. To see an effect against the normal moonlight a contrast brightness change of at least 10% is necessary representing an incremental light flux from the surface of the order of 10⁻² W cm⁻². The most likely cause of such a change is a change in the albedo. The low albedo of about 7% is a factor of 2 or 3 times lower than that of a terrestrial basaltic dust of similar composition. This is because of the “fairy castle” structure of the lunar dust, giving deep intergrain penetration of sunlight and little return except in the incidence direction. If this structure could be destroyed by breaking of the intergrain cohesion, then the albedo would rise. This could be achieved if the dust was “fluidized”. Such a process has already been associated with TLPs by Mills⁷ but he assumes that the TLP is seen because of the light emission caused by electrical discharges in the venting gases between grains. But the efficiency of excitation of such discharges will be rather low and the same kind of estimate as that made by Nash et al.³ for the luminescence of lunar dust will apply.