Lunar Rays
The physical nature of lunar rays has historically been a subject of speculation. Early hypotheses suggested that they were deposits of salt from evaporated water. Later they were thought to be deposits of volcanic ash or streaks of dust. After the impact origin of craters became accepted, Eugene Shoemaker suggested during the 1960s that the rays were the result of fragmented ejecta material.
Recent studies suggest that the relative brightness of a lunar ray system is not always a reliable indicator of the age of a ray system. Instead the albedo also depends on the portion of iron oxide (FeO). Low portions of FeO result in brighter materials, so such a ray system can retain its lighter appearance for longer periods. Thus the material composition needs to be factored into the albedo analysis to determine age.
Among the lunar craters on the near side with pronounced ray systems are Aristarchus, Copernicus, Kepler, Proclus, and Tycho. Similar ray systems also occur on the far side of the Moon, such as the rays radiating from the craters Giordano Bruno and Ohm.
Read more about this topic: Ray System
Famous quotes containing the words lunar and/or rays:
“A bird half wakened in the lunar noon
Sang halfway through its little inborn tune.”
—Robert Frost (1874–1963)
“The rays which stream through the shutter will be no longer remembered when the shutter is wholly removed.”
—Henry David Thoreau (1817–1862)