From: salsa.the.geek@gmail.com   
      
   I'm working on a planetary system generator, and I've come to the realization   
   that there's not a formal classification system for planets, or at least not   
   one that I have found. Naturally, I felt this needed addressing, so I've come   
   here to get some    
   feedback on my first stab at coming up with one.   
      
   Mercurian - Rocky planet little to no atmosphere, no surface ice, and no   
   icy/hydrous mantle.   
   Terrestrial - Rocky planet with an atmosphere.   
   Gaian - Terrestrial that is habitable by life as we know it.   
   Ceresian - Rocky planet with no surface ice/water, but has an icy/hydrous   
   mantle beneath the crust.   
   Kuiperian/Plutonian - Icy/rocky planet with surface ice.   
   Uranian - A gas/ice giant that is not massive enough to produce metallic   
   hydrogen.   
   Jovian - A gas/ice giant that is massive enough to produce metallic hydrogen,   
   but not massive enough to start nuclear fusion.   
   Brown Dwarf - a body that is massive enough to start nuclear fusion, but is   
   not undergoing nuclear fusion.   
      
   And it'd probably be useful to define some things which might come up.   
      
   Planet - An object massive enough to be rounded by it's own gravity.   
   Protoplanet - An object that isn't massive enough to be fully-rounded, but is   
   massive enough to have produced a differentiated interior.   
   Double (Proto)Planet - A pair of planetary objects that are gravitationally   
   bound to each other and where the barycenter of the system is beyond the   
   surface of either object.   
      
   Defining things this way neatly avoids having to write a few hundred words to   
   define the difference between a planet and a dwarf planet. If Pluto was in an   
   orbit where its "neighborhood" was clear of similar sized bodies, would it   
   still be a dwarf planet?   
    Anyway, I'm getting off topic in my own opening post.   
      
   So, applying this to the Solar System, Mercury is a Mercurian. Venus and Earth   
   are Terrestirals, but Earth is, to be more specific, a Gaian. Mars is also a   
   Terrestrial, but I'd say it's close to a borderline Mercurian. Basically, the   
   dividing line is    
   whether the atmosphere is substantial enough to have a practical effect on   
   something passing through it. Ceres is a Ceresian. Vesta is a Mecurian   
   protoplanet, though I might be wrong about it being big enough to have some   
   differentiation. Jupiter and    
   Saturn are Jovians. Uranus, Neptune, and the hypothetical Planet 9 are all   
   Uranians. Pluto, Makemake, Hamuea, and all the other Kuiper Belt objects that   
   are planets as defined above are Kuiperian/Plutonian.   
      
   If we wanted to apply this to some fictional planets, then Hoth would be a   
   Kuiperian/Plutonian Gaian because it is a icy/rocky planet with surface ice   
   and is habitable by life as we know it. Tatooine and Arrakis are Gaians,   
   because while they may have    
   had water underground, they didn't have icy/hydrous mantles.   
      
   So, any suggestions or comments? I thought about adding classes for Hot   
   Jupiters, but I think it's better to define the planet by its characteristics   
   that are at least somewhat independent of its orbit.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)