Lunar transient phenomena: What do the clementine images reveal?

Lunar Transient Phenomena (LTP) have been reported for at least 450 years. The events range from bright flashes, to reddish or bluish glows, to obscur ations. Gaseous spectra and photometric measurements of the events have bee n obtained. Several theories have been offered as explanations for LTP, inc luding residual volcanic activity or outgassing, bombardment by energetic p articles, and piezoelectric effects. As the first set of digital multispect ral images of the entire Moon, the Clementine data offer a unique opportuni ty to couple inferences of compositional relationships with lunar geomorpho logy in the regions of LTP. We have selected 11 regions from which numerous reliable historical reports of LTP exist. Our analysis of the Clementine m ultispectral images shows that many events occur in regions of bright, spec trally reddish deposits, which may be characteristic of volcanic ejecta. Th e events may be associated with outgassing of volatiles collected in or ben eath mare basalt flows, We find that LTP tend to occur near the edges of ma ria, in agreement with a suggestion originally made by Cameron (1972, Icaru s 16, 339-387), and in other regions of crustal weakness. We also find that some of the reported events tend to be in craters with rims of distinctly different (bluer) composition. This compositional difference may result fro m recent slumping of the rim, accompanied by the appearance of fresher unde rlying material. In some cases, slumping may be triggered by the release of pockets of volatiles; in turn the slumping events may cause additional poc kets of trapped material to be released. There are four instances in which Clementine multispectral images were acqu ired both before and after an event that was reported by a terrestrial team of amateur astronomers mobilized to observe the Moon during the mapping ph ase of Clementine. None of these four sets of images shows clear changes th at could be attributed to the reported LTP. (C) 2000 Academic Press.