21.   They are distinguished also by bright pinwheel-shaped features filled with stars that curve from a central structure that emitted a faint orange glow in the Hubble images.

22.   Under these conditions, the astronomers were able to detect the faint glow of sodium gas, which serves as a marker for other gases in the lunar atmosphere.

23.   Now the visitors can distinguish a faint glow that grows stronger as they make for the exit.