Astronomers: Liquid oceans may be normal in universe

Based on a computer simulation, scientists state that subterranean oceans may be much more common in the universe than previously thought. The simulation indicates that gas hydrates are likely responsible for the existence of an ocean on Pluto.

An international team of scientists, including members from Japan’s Hokkaido University, says there is compelling evidence that an insulating layer of gas hydrates prevents a subterranean ocean below Pluto’s surface from freezing. According to the astronomers, the insulating effect of gas hydrates means that subterranean oceans can exist in other relatively large icy moons and other distant objects, without a source to generate heat. “This could mean that there are more oceans in the universe than previously thought, making the existence of extraterrestrial life more plausible,” said Shunichi Kamata, the leader of the research team.

For several years, scientists have suspected that there is an ocean beneath Pluto’s ice surface. That hypothesis was co-formulated after NASA’s New Horizons spacecraft flew past Pluto in 2015 and took the first close-up photos. It showed an unexpected topography, such as a white basin called Sputnik Planitia, which is located near the equator. Scientists suspected that a subterranean ocean existed under Sputnik Planitia’s relatively thinner ice sheet, but that statement is inconsistent with Pluto’s age; the ocean should have frozen long ago, which is partly due to Pluto’s great distance from the sun and the lack of a large object or planet nearby that can provide a heat source through gravity.

The research team hypothesized that an insulating layer of gas hydrates sits beneath the ice surface of Sputnik Planitia. Gas hydrates are ice-like compounds of gas and crystal water, often involving methane. To test the hypothesis, computer simulations were run, setting a time lapse of 4.6 billion years from when the solar system began to form. Two scenarios have been simulated: one where the layer of gas hydrates is present and a second where there is no such layer between the top ice layer and the ocean. This shows that in the absence of gas hydrates, an underground sea would be completely frozen after hundreds of millions of years. According to the scientists, the results support the possibility of a long-standing liquid ocean beneath the ice crust of Sputnik Planitia. They think the gas is methane, which would come from Pluto’s rocky core.

The research is published in the scientific journal Nature Geoscience under the title Pluto’s ocean is capped and insulated by gas hydrates.