What sort of atmosphere could a rogue planet have?

[CCWilson]

Let's say that a planet of approximately Earth's size - containing, as Earth does, core heat - were tossed out of orbit. Could it maintain any sort of atmosphere, or would all the component gases liquify and freeze, or be gradually lost to space? If it could retain any atmosphere, what gaseous elements would be most likely?

 

[Mordred]

Well the planets gravity is what keeps the atmosphere. most of the gases however would solidify. However that would also depend on its internal temperature. The question is highly varied so difficult to answer as their are so many variables involved.

 

[CCWilson]

I saw on the internet speculation that some rogue planets - and apparently there are a lot of them in the universe - might be able to retain a heavy atmosphere, enough to allow the possibility of life. However, the gas mentioned was hydrogen, which wouldn't sustain our kind of life, although it might keep the temperature slightly warmer. The gases in our atmosphere with the lowest liquifying/freezing points are hydrogen, neon, and helium, by the way.

But take planet Earth as an example. Any idea whether its internal temperature would be enough to keep nitrogen and oxygen from liquifying? There's not much hydrogen, neon, or helium in our atmosphere.