An ocean on Pluto, which has long been thought to be frozen over, could actually only be covered by an insulating gas cloud, scientists say.
The new research suggests that there may be more oceans in the universe than previously thought and increase the likelihood of extraterrestrial life.
In July 2015, NASA's New Horizons spacecraft flew through Pluto's system, providing the first close-up of the distant dwarf planet and its moons.
After analyzing the images, the scientists believed that an underground ocean had to exist beneath an ice sheet that thinned in a Texan basin called Sputnik Planitia.
The team of the Japanese Hokkaido University, the Tokyo Institute of Technology, Tokushima University, Osaka University, Kobe University and the University of California in Santa Cruz believed that the ocean should have frozen millions of years ago.
However, the land formation shown in the pictures contradicted previous ideas about the surface, as the inner surface of the ice bowl facing the ocean had to appear flat.
In the new study, published in the journal Nature Geoscience, researchers created computer simulations for a period of 4.6 billion years as the solar system began to form to simulate two scenarios.
The simulations showed that the subterranean sea would have frozen for hundreds of millions of years without an insulating layer of gas hydrate, as it would have taken only a million years for the ice crust to completely form over the ocean.
However, the results suggest that the ocean with the insulating layer barely freezes and slows the process from one million to one billion years.
The team believes, therefore, that there must be an "insulating layer" of crystalline, ice-like solids that consists of gas and is trapped in submerged molecular water cages.
Since these gas hydrates are highly viscous and have a low thermal conductivity, they can develop an insulating effect.
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The team is of the opinion that the insulating layer is likely to be methane from the rocky core of Pluto – because the Pluto atmosphere is low in methane and rich in nitrogen.
Similar insulating gas hydrate layers could sustain other subterranean oceans in other icy moons and distant celestial objects, the team said.
Senior author, associate professor Shunichi Kamata of Hokkaido University, said, "This could mean that there are more oceans in the universe than previously thought, making the existence of an alien life more plausible."