earth had hardly any ocean, just rock and volcanoes (hot core), how it had hot core im not sure , more the density of gravity was 'just right' along with the drawn in materials from space was also 'just right'...over a looong period of time, the overflowing ceased...some how the cooling took place with the layers of gases remained within the gravitational pull, hence this layer eventually become atmosphere then over a loooong period of time some kind of reaction took place where the surface become opitimised for life....
it would be interesting to know whether planets have nitrogen breathing lifeforms, how it is possible for this to occure what kind of orgaism evolved to relate to that particular atmospherical condition (and suface?, soil, rock, crystals, even - metal laden? )...intelligence would be another thing altogether...perhaps the evolution of life/creatures took place too but under a whole different sets of atmospherical conditions and regulations by plants or pools of liquid form of nitrogen (LN2 lake???) who knows...
LN2 freezed super cold is actually founded and recorded to be 'equal' to the coldest part of the universe. On Earth, radiowave scientists actually accidentially found this out.
perhaps another criteria, is the sun's size and age, as it might emit different wavelengths which might be contributing factor deciding if life can take place or even what forms...?
blah i think i raved abit too much here just enjoyed this splash of imagination about planetary science lol
cheers