Ok, I found this here: http://phl.upr.edu/library/notes/ama...rasolarplanets
It seems to be a scientifically based classification system. I think Christopher is on to something and if we look at adding in sub-categories to include common sci fi issues such as survivability using pressure suits and pressure domes and ship survivability as key points in the subcategories.
Planet Type Mass (Earth Units) Radius (Earth Units)Potential Atmosphere*
Asteroidan 0 - 0.00001 0 - 0.03Asteroidans are small irregular bodies (below the hydrostatic equilibrium) that are not able to hold a stable atmosphere.
Mercurian 0.00001 - 0.1 0.03 - 0.7Mercurians are only able to hold a significant atmospheres in the cold zones beyond the snow line (i.e. Titan).
Subterran 0.1 - 0.5 0.5 - 1.2Subterrans are able to hold a significant atmospheres after the outer edges of the habitable zone (i.e. Mars).
Terran 0.5 - 20.8 - 1.9
Terrans are able to hold a significant atmosphere with liquid water within the habitable zone (i.e. Earth).
Superterran 2 - 10 1.3 - 3.3Superterrans are able to hold dense atmospheres with liquid water within the habitable zone.
Neptunian 10 - 50 2.1 - 5.7Neptunians can have dense atmospheres in the hot zone.
Jovian 50 - 5000 3.5 - 27Jovians can have superdense atmospheres in the hot zone.
* The cold zone
is the zone farther from the star after the habitable zone (which includes the snow line), the hot zone
is the zone between the star and the habitable zone.