It is shown that from the appearance of certain photographs taken from STS-5, it is possible to make several useful statements about the production mechanism of the visible glow around the shuttle, and presumably other space vehicles. These are: 1) the electronic excitation of particles in the gas phase by either electrons or fast neutrals is probably not important, 2) the interaction of thermal atoms and molecules with the surface does not generate the glow, and 3) translational energy accommodation of fast particles is efficient enough that a single surface collision reduces the kinetic energy below the threshold for glow production. There is no glow without the direct interaction of fast particles with the surfaces, and the sum of the contributions of the three above processes does not exceed 14% of the observed surface intensity.