Scientists think they know how the hidden ocean of Pluto remains liquid

Recent results suggest that Pluto has an ocean of liquid water buried under its icy shell. But how could such a thing be possible on the icy outer limits of the solar system? Scientists from Japan and the United States may have an answer.

In an article published Monday in Nature Geoscience, these researchers speculate that the ocean of Pluto may be kept isolated by a layer of gas under the ice. If this assumption turns out to be true, then this mechanism could prevent other icy worlds from freezing completely.

"If this mechanism is common, then the oceans could be common on other major [Kuiper Belt objects], Co-author of the study, Francis Nimmo of the University of California at Santa Cruz, told Gizmodo.

The document is primarily an inference based on the combination of other evidence. The New Horizons mission flew over Pluto in 2015 and discovered that it was quite geologically complex. In 2016, scientific models suggested that Sputnik Planitia, the left lobe of the "heart" of the dwarf planet, could have a partially liquid underground ocean such as the frozen moons of Jupiter or Saturn.

It's wild enough to think: something as distant and as small as Pluto is not completely frozen, but could have liquid water beneath its surface. Scientists have wondered how this could be possible. Pluto does not have the gravitational energy of a huge planet nearby to maintain the tides and help warm the water. According to the new document, the warming due to the radioactive decay of its elements would not prevent a complete freeze. And there does not seem to be enough ammonia in Pluto to dissolve in water and increase its melting point.

Instead, scientists suggest that the ice shell has a layer of ice cages containing gas, such as methane, inside. Without the layer, the ice would absorb heat from the inside of Pluto. But the "clathrate hydrate" caged gas layer would have different thermal properties that would slow down the ice's ability to capture the heat of the water. And the trapping of methane would also explain why scientists have not observed much methane in Pluto's atmosphere, said Nimmo.

The document is "very interesting," Gizmodo J. Hunter Waite, a program director at the Southwest Research Institute, said, not involved in this study. "Understanding the role of processes such as the formation of clathrates expands the knowledge base to explore the oceanic worlds and their role in the formation and evolution of the solar system, broadening our horizons in defining living environments." he continued.

But he warned that scientists were still unaware of Pluto's overall makeup and had to turn to other objects, such as comets and meteorites, to guide their assumptions.

It's still interesting. "Our results suggest that an ocean of long life can exist even without warming tides, which is important for keeping the oceans in icy satellites," said Gizmodo, the first author of the study, Shunichi Kamata from Hokkaido University in Japan.

New Horizons whistled far beyond Pluto, and there is no current mission that can verify the existence of these clathrate hydrates. But Nimmo and Kamata hope that in the future some missions will be able to verify their conclusions. And maybe there are other frozen oceans around the solar system that are kept warm in the same way.