Pluto discovery suggests vast oceans hide beneath gassy bubble

21 May 2019

Image: © Fox/

More vast oceans could be hiding beneath the surface of Pluto than we once thought, hidden by an insulating layer of gas.

The solar system’s most famous dwarf planet continues to impart more knowledge about our universe following 2015’s New Horizons flyby that revealed the first ever close-up image of Pluto and its moons.

Researchers from five different Japanese universities have announced that there is now compelling evidence for the existence of a thick, insulating layer of gas hydrates hiding significantly more vast oceans beneath the dwarf planet than once thought.

Computer simulations have shown that this gas bubble could be enough to prevent the oceans from freezing, and the same could be said for countless other undiscovered planets across the universe.

Following the New Horizons flyby, scientists noted the unexpected topography of the planet, most notably the heart-shaped, white-coloured basin named Sputnik Planitia. At the time, it was suggested that a subsurface ocean could be found beneath the ice shell at Sputnik Planitia.

However, if this were the case, the age of the planet means that any oceans would have frozen over a long time ago and the inner surface of the ice shell facing the ocean would have also flattened. The Japanese researchers, publishing their findings to Nature Geoscience, theorised what could keep an ocean warm enough from freezing over, eventually leading to the hypothesis of the gaseous insulating layer.

Gas hydrates are crystalline ice-like solids formed from gas trapped within molecular water cages. They are highly viscous and have low thermal conductivity, so could therefore provide insulating properties.

More life in the universe

To test this, the researchers ran two computer simulations covering the 4.6bn years of the solar system’s life so far. This showed the thermal and structural evolution of the interior of Pluto and how long it would take for a subsurface ocean to freeze and its icy shell to become uniformly thick.

The first simulation looked at where an insulating layer of gas hydrates existed between the ocean and the icy shell, and one where it did not. This showed that without a gaseous insulating layer, the oceans would have frozen over hundreds of millions of years ago, but not if it has one.

Also, the researchers showed that it would take 1m years for a thick ice crust to form over Pluto, but more than 1bn years with a gaseous layer. In the case of Pluto, the gas is most likely methane originating from its rocky core. This is consistent with the unusual composition of the planet’s atmosphere, which is methane-poor but rich in nitrogen.

The researchers suggested that similar layers could be hiding subsurface oceans in other planets and moons in the universe.

“This could mean there are more oceans in the universe than previously thought, making the existence of extraterrestrial life more plausible,” said Shunichi Kamata of Hokkaido University, who led the team.

Colm Gorey was a senior journalist with Silicon Republic