Thick Oxygen/Nitrogen atmosphere.  Specific gravity within 0.7 to 1.3 Earth
normal.  Random, but mostly manageable weather patterns, with temperatures
ranging from 0 to 40 degrees Celsius.  Fertile soil, excellent for Organic
production.  Mineral deposits, very good for Equipment production.  Chemical
elements good for Fuel Ore.  Class M planets are excellent for human
colonization and promote an excellent population growth curve as well as a
very good population harmony quotient.  They have an above average
"habitability band".  Drawbacks include overpopulation problems, political
unrest and human-induced destruction of the BioSphere.
