It appears as though a liquid ocean is presently underneath Sputnik Planitia on the dwarf planet Pluto. It was believed that the temperate needed for an ocean to remain in liquid format on Pluto would have been too high because the thick ice would have melted. However, Japanese astronomers claim there is a layer of gas located underneath the ice and above the liquid which works as a type of insulation between the two.
This is very exciting news for scientists as they previously believed that all the water on Pluto would have been in a frozen state. The research, which was published in Nature Geoscience, read in part, “To maintain an ocean, Pluto needs to retain heat inside. On the other hand, to maintain large variations in its thickness, Pluto’s ice shell needs to be cold.” Additionally, they wrote, “Here we show... that the presence of a thin layer of clathrate hydrates (gas hydrates) at the base of the ice shell can explain both the long-term survival of the ocean and the maintenance of shell thickness contrasts.” They better explained how the clathrate hydrates work by writing, “Clathrate hydrates act as a thermal insulator, preventing the ocean from completely freezing while keeping the ice shell cold and immobile.”
As for the type of gas, they explained that “The most likely clathrate guest gas is methane, derived from precursor bodies and/or cracking of organic materials in the hot rocky core. Nitrogen molecules initially contained and/or produced later in the core would probably not be trapped as clathrate hydrates, instead supplying the nitrogen-rich surface and atmosphere.”
Researchers created a simulation of Pluto’s evolution, with and without a gas hydrate layer between the ice and the ocean in order to calculate how long it would take for the subsurface oceans to freeze over. They calculated that without the gas hydrate layer, the ocean would have been totally frozen around 800 million years ago. However, with the gas hydrate layer, the ocean hardly froze at all. In conclusion, without a gas hydrate layer, it would have taken the subsurface ocean approximately 100 million years to freeze over, but with the gas layer, it would take more than a billion years.
The simulation based on observations conducted by New Horizons not only shows the real possibility of a liquid ocean on Pluto, but it also gives a plausible explanation as to how the most iciest planets can still contain water in liquid format.