The honor of the first recorded intermittent lunar phenomenon belongs to the astronomer William Herschel, on April 19, 1787. This phenomenon involves short-term changes in the appearance of certain regions of the lunar surface, manifesting as bright flashes, colored spots, or hazy formations. But what are the causes of these events? The portal livescience.com attempted to explore this question. A spectrum of physical processes could underlie the unexplained flashes on the Moon, but the duration of a specific lunar event allows for the determination of its probable cause. For example, if the flashes last less than sixty seconds, they are most likely caused by meteoroid impacts. Objects with a mass of about 0.2 kg (comparable in weight to a standard billiard ball), upon colliding with the lunar surface, generate light flashes. The source of the light itself is the impact energy, which heats lunar rocks to incandescence. Although such collisions have long been considered a cause for ultra-fast flashes, the scientific community could not obtain direct confirmation until the 1990s, when high-speed cameras became available. Even with their advent, the very short duration of the flashes made it difficult to entirely rule out the influence of external factors, such as electrical noise. For this reason, verifying the flashes required simultaneous observation from at least two different locations. Despite this limitation, some of these phenomena were first confirmed during the Leonid meteor shower in November 1999. Since then, astronomical programs have officially registered hundreds of similar events. Within the NELIOTA project, overseen by the ESA, 193 lunar flashes were documented over nine years. Analysis of their spatial distribution suggests that the impacts occur in specific “hot spots,” such as Oceanus Procellarum—a region potentially active tectonically. However, some experts suggest that this pattern might only be a result of bias in data collection. Glows on the Moon lasting for several minutes may result from radon escaping from beneath the planet’s surface. Scientific papers published in 2008 and 2009 in The Astrophysical Journal proposed the hypothesis that such glows arise from the sudden breakthrough of accumulated gases to the lunar surface due to tectonic activity. Radioactive radon emits light upon its decay, making it visible from Earth. Moreover, locations where prolonged glowing has been observed correlate with areas where high concentrations of radon have been detected. There are also flashes visible for hours. Such phenomena, at least according to a 2012 study, may only be indirectly related to the Moon. The authors of this work suggested that the solar wind causes the ionization of lunar dust particles, leading to the formation of fast cloud structures. These clouds, in turn, can reflect light from stars or other bright objects located near the Moon. Nevertheless, a portion of the scientific community questions the very existence of long-duration flashes.
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