Extremely thin Oxygen-Nitrogen atmospheres.  Specific gravity from 0.5 to
1.7 Earth normal.  Meteorologically unstable causing violent conditions.
Temps range from -10 to -190 degrees Celsius.  Full life support necessary
for colonies and death rates are high.  No workable soil base so hydroponic
Organics are limited.  Modest mineral and chemicals exist so production of
Ore and Equipment will be below average to none.  Class C planets NOT
recommended for colonization, their violent condition makes it extremely
hazardous.  Some Class C planets have been adopted by the Federation and used
as prison colonies with very effective results.