There's much about Pluto that remains a mystery, but in the outer reaches of the solar system, its temperatures are well below freezing levels.
With the dwarf planet's icy shell of nitrogen, scientists have been hard-pressed to explain the liquid ocean that has been found lying in the heart of Pluto.
Now, a team of researchers from Japan and United States believe they've found the answer: a layer of gas hydrates between the frozen surface and the liquid ocean that separates and insulates the two regions. The scientists share evidence of an insulating layer preventing subsurface liquid from freezing in a new study published in the journal Nature Geoscience.
Back in 2015, NASA's New Horizons spacecraft flew near Pluto and captured images that showed evidence of a hidden ocean under an ellipsoidal basin known as Sputnik Planitia.
Upon learning of a possible liquid ocean lurking in Pluto, the team considered what could keep a liquid ocean warm in frozen Pluto. One promising hypothesis is the existence of an insulating layer of gas hydrates, which crystalline solids made out of gas in molecular water cages.
With computer simulations spanning since the birth of the solar system 4.6 billion years ago, the scientists analyze the evolution of Pluto's interior. In one scenario, the insulating layer of gas hydrates were included, while in another, it was not.
Results were simple: without the gas hydrates, the liquid ocean would have completely frozen over hundreds of millions of years ago. However, the presence of an insulating layer allows the ocean to persist hardly freezing at all over the same span of time.
According to the study authors, the gas in the insulating layer is most likely methane, which comes from the dwarf planet's core. This hypothesis is compatible with Pluto's atmosphere, which is low in methane and rich in nitrogen.
More Liquid Oceans In Icy Worlds
If an insulating layer of gas hydrates is possible in Pluto, it could also potentially exist in other frozen worlds throughout the universe. This means that water could be present in more celestial objects than initially assumed. With water essential for life, the new findings lets researchers cast a wider net in the search for alien lifeforms in the universe.
"This could mean there are more oceans in the universe than previously thought, making the existence of extraterrestrial life more plausible," explained study leader Shunichi Kamata of Hokkaido University.