Copper;bright with somewhat blue edge

effects, but numerous data support the reality of the phenomena: Short (1975, p. 64) reports over 1200 citings of localized lunar brightenings, more than 300 of which have been associated with the Aristarchus crater. Link (1969, 88ff) summarizes and describes some of the evidence. The darkness of the moon during eclipse has been correlated with the solar cycle (see Link 1969, pp. 97-100). The astronomers Danjon (1920a,b) and de Vaucouleurs (1944) found that the brightness of the eclipsed Moon increases with phase of the 11-year cycle and drops sharply at the end of the cycle, so that the darkest Moon coincides with the beginning of the new cycle, when sunspots are few and are located at high solar latitudes. Matsushima (1966) found a correlation with the geomagnetic Kp index, which measures the strength of local geomagnetic effects of the solar activity cycle. As noted elsewhere, the reddening may be influenced also by the suspension of particles in the Earth's atmosphere, but Link (1947, 1969, p. 99) interprets the Danjon relation as evidence for luminescence excited by solar wind particles. Danjon's luminosity scale, created for prephotometric measurements, and therefore appropriate to apply to ancient eclipse descriptions, is indicated in Table 5.5.

Lunar volcanism is not considered a likely source of lunar events, although one observation of a possible volcanic event was reported by Kozyrev (1962), based on a spectro-scopic observation of possible volcanic outgassing from the lunar crater Alphonsus. No further event has been seen, and so the existence of active volcanism on the Moon has not been confirmed. The current theory of the Moon's interior calls for a cold crust and upper mantle, with seismic disturbances limited to a region 700 to 1200 Km beneath the surface. This is not the kind of model for which surface vol-canism is expected, and Opik (1977) suggested that a more likely explanation for Kozyrev's observation was luminescence from a sunlit peak. Despite a body of anecdotal material from visual observers about such enhanced brightenings, convincing measurements seem to be lacking.

0 0

Post a comment