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, Dionysius, Glushko, and Tycho. Smaller examples include Censorinus, Stella, and Linné. Similar ray systems also occur on the far side of the Moon, such as the rays radiating from the craters Giordano Bruno, Necho, Ohm, Jackson, King, and the small but prominent Pierazzo. Most lateral transport of primary ejecta from impact craters is limited to a distance of a few crater radii, but some larger impacts, such as the impacts that made the Copernicus and Tycho craters, launched primary ejecta halfway around the moon. North Ray and South Ray craters, each with a clear ray system, were observed from the ground by the astronauts of Apollo 16 in 1972. See also List of craters with ray systems Reiner Gamma References Citations Sources Martel, L.M.V. (Sept., 2004) Lunar Crater Rays Point to a New Lunar Time Scale, Planetary Science Research Discoveries. http://www.psrd.hawaii.edu/Sept04/LunarRays.html. (Accessed 9/15/2005) Burnham, R. (March, 2005) Chipping pieces off Mars: Martian craters with rays may be the long-sought sources for the Mars meteorites found on Earth, Astronomy Magazine Online. http://www.astronomy.com/asy/default.aspx?c=a&id=2980 (Accessed 8/07/2006) Impact craters