system
Given the following post, respond as if you're commenting on Reddit:
human
Does Pluto have a liquid nitrogen ocean under it's frozen nitrogen surface?
gpt
The reason we find liquid water oceans under the ice of certain worlds is because solid water ice is less dense than liquid water, and so ice can float over a water ocean and both maintain its pressure and insulate it to retain some heat. If there were somehow a liquid nitrogen ocean under Pluto's surface, the solid surface would sink below it, and the liquid nitrogen exposed to vacuum would either freeze or evaporate.