On the basis of a computer simulation, scientists state that subterranean oceans may occur much more frequently in the universe than previously thought. The simulation indicates that gas hydrates are probably responsible for the existence of an ocean on Pluto.
Pluto structure An international team of scientists, including members from Japan’s Hokkaido University, argue that there is convincing evidence that an insulating layer of gas hydrates prevents an underground ocean from freezing beneath Pluto’s surface. According to astronomers, the isolating effect of gas hydrates means that subterranean oceans can exist in other relatively large ice moons and other distant objects, without a source of heat being generated. “This could mean that there are more oceans in the universe than previously thought, making the existence of extraterrestrial lives more likely,” said Shunichi Kamata, the leader of the research team.
For several years, scientists have suspected that there is an ocean beneath the ice surface of Pluto. This hypothesis was partly formulated after NASA’s New Horizons spacecraft had flown past Pluto in 2015 and had taken the first pictures up close. There was an unexpected topography on it, such as a white basin with the name Sputnik Planitia, which is located near the equator. Scientists suspected that an underground ocean exists under the relatively thinner ice layer of Sputnik Planitia, but that proposition cannot be reconciled with the age of Pluto; the ocean should have been freezing for a long time, which is partly due to Pluto’s great distance from the sun and the lack of a large object or planet nearby that can cause a heat source through gravity.
The research team hypothesized that an insulating layer of gas hydrates is located below 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 the moment the solar system began to form. Two scenarios have been simulated: one where the layer of gas hydrates is present and a second situation where such a layer is missing between the upper 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 under the ice crust of Sputnik Planitia. They think the gas is methane, which would come from the rocky core of Pluto.
The research is published in the scientific journal Nature Geoscience under the title Pluto’s ocean is capped and insulated by gas hydrates.