I can think of a place other than the moon where NASA could develop a closed life-support system for staging rehearsals of manned Mars exploration. Why not Earth? Advantages would include a protective atmosphere, a day length closer to the Martian sol, bone-and-muscle-friendly gravity, and easy access to mechanical and medical resources. The cost would be much less than that of a moon base, and crew rotation would involve motor vehicles rather than launch vehicles. Why not keep the rehearsal safe and relatively cheap?

Jeffry D. Mueller
Eldersburg, Md.