In a few instances astronomers have been able to photograph the color spectrum of a meteor in flight, to analyze the spectral lines and determine exactly what elements were present[V-10]. As a rule, however, the chemical content must be found from a laboratory analysis of recovered meteorites. Some meteors do contain traces of copper, and free nodules of pure copper have been found in several meteorites [V-5, p. 81]. Magnesium occurs in fairly high percentages in most meteorites and the amount is unusually high in green meteors[V-11]. It produces a color almost identical with that from copper. Seeing the green of a vaporizing meteor, no observer could tell whether the color came from copper or from magnesium unless he could photograph the spectrum or make a chemical analysis of the meteorite. The color displayed by the New Mexico fireballs may have come from copper, but more probably from magnesium. Another possible source is frozen nitrogen. Laboratory experiments relating to problems of satellite re-entry[V-12] have shown that when frozen nitrogen vaporizes, it emits a brilliant green glow whose wave length is almost identical with that of the New Mexico fireballs, as judged from the paintings made by witnesses. One of the prevailing theories suggests that meteors of this type may be icy “cometoids”--cometary debris, chunks of ice, and frozen gases (including nitrogen) at very low temperatures. When they enter the earth’s atmosphere and are slowed down to speeds of several hundred miles an hour, they become heated and vaporize, and the surface alternately melts and refreezes; the vaporizing nitrogen would produce the green color seen in the fireballs. Such a process would account for the color, the short lifetime, and the lack of fragments of the New Mexico meteors. To summarize: Meteors _can_ exhibit the particular green color shown by the New Mexico fireballs. It can result from copper, magnesium, or frozen nitrogen, which can normally occur in meteors.